Preparation, structure, and unique thermal [2 + 2], [4 + 2], and [3 + 2] cycloaddition reactions of 4-vinylideneoxazolidin-2-one

Article abstract of DOI:10.1002/chem.200304586

The terminal allene C_α=C_β bonds of 4-vinylidene-2-oxazolidinone (2) readily undergo [2 + 2] cycloaddition with a wide variety of terminal alkynes, alkenes, and 1,3-dienes irrespective of their electronic nature under strictly thermal activation conditions (70-100°C) and provide 3-substituted (Z)-methylenecyclobutenes 6, 3-substituted methylenecyclobutanes 7 and 8, and 3-vinylmethylenecyclobutanes 9, respectively, in good to excellent yields. Alkenes react with 2 with complete retention of configuration. The [2 + 2] cycloaddition is concluded to proceed via a concerted [(π_2s + π_2s)_allene + π_2s] Hueckel transition state on the basis of experimental evidences and quantum mechanical methods. Some highly polarized enones and nitrile oxide, on the other hand, react with 2 selectively at the internal C₄=C_α double bonds and give spiro compounds 10 and 11, respectively. The bent allene bonds (173-176°) and the unique reactivity associated with 2 are attributed to a low-lying LUMO (C_α=C_β) that is substantiated by a through-space σ*(N-SO₂)-π*(C_α= C_β) orbital interaction.

Full text of DOI:10.1002/chem.200304586

FULL PAPER
Preparation, Structure, and Unique Thermal [2 ‡ 2], [4 ‡ 2], and [3 ‡ 2]
Cycloaddition Reactions of 4-Vinylideneoxazolidin-2-one
Yoshikazu Horino,[a] Masanari Kimura,[a] Shuji Tanaka,[a] Toshiya Okajima,[b] and
Yoshinao Tamaru*[a]
ˆ
Abstract: The terminal allene Ca Cb
bonds of 4-vinylidene-2-oxazolidinone
(2) readily undergo [2 ‡ 2] cycloaddition
with a wide variety of terminal alkynes,
alkenes, and 1,3-dienes irrespective of
their electronic nature under strictly
thermal activation conditions (70
1008C) and provide 3-substituted (Z)-
methylenecyclobutenes 6, 3-substituted
methylenecyclobutanes 7 and 8, and
3-vinylmethylenecyclobutanes 9, respec-
tively, in good to excellent yields. Al-
kenes react with 2 with complete reten-
tion of configuration. The [2 ‡ 2] cyclo-
addition is concluded to proceed via a
concerted [(p2s ‡ p2s)allene ‡ p2s] H¸ckel
transition state on the basis of exper-
imental evidences and quantum me-
chanical methods. Some highly polar-
ized enones and nitrile oxide, on the
other hand, react with 2 selectively at
ˆ
the internal C4 Ca double bonds and
give spiro compounds 10 and 11, respec-
tively. The bent allene bonds (173 1768)
and the unique reactivity associated with
2 are attributed to a low-lying LUMO
ˆ
(Ca Cb) that is substantiated by
a
Keywords: alkenes
¥
alkynes
¥
ˆ
through-space s*(N-SO2) p*(Ca Cb)
orbital interaction.
allenes ¥ cycloaddition ¥ dienes
R
Introduction
Owing to their inherent strain, allenes have been recognized
as an active and excellent reaction partner for many types of
cycloaddition reactions. Especially, [2 ‡ 2] cycloaddition of
allenes with alkenes has been of special interest because of the
synthetic importance of the reaction, providing methylenecy-
clobutane units of structural interest.
The Woodward Hoffmann rule and the Fukui frontier
orbital theory predict that [2 ‡ 2] cycloaddition is photo-
chemically allowed, but thermally forbidden. In accord,
photochemical reactions of allenes proceed smoothly and
provide products with expected regio- and stereochemistry in
good yields and have been utilized for the syntheses of natural
and unnatural products of structural complexity.[1] On the
other hand, thermal [2 ‡ 2] cycloaddition of allenes requires
high temperatures (>2008C) and/or long reaction times. This
process has suffered from low regio- and stereoselectivity, and
O
NTs
Ar
Ar
6
O
N
O
R
O
NTs
O
NTs
O
11
O
7
β
O
N
C Ar
•
Ar
W
α
4
O
NTs
O
O
2
W
O
O
NTs
O
NTs
O
10
O
8
O
NTs
W = electron
withdrawing group
O
9
[a] Prof. Y. Tamaru, Dr. Y. Horino, Dr. M. Kimura, Dr. S. Tanaka
Department of Applied Chemistry
Scheme 1. Regio- and stereoselective, [2 ‡ 2], [4 ‡ 2] and [3 ‡ 2] cyclo-
addition of 2.
Faculty of Engineering, Nagasaki University
1-14 Bunkyo-Machi, Nagasaki 852-8521 (Japan)
Fax : (‡81)95-847-9008
in general, low yields of the methylenecyclobutane products.[2]
Therefore, as an alternative, a variety of methods relying on
activation of allenes (e.g., allene carboxylic esters and
heteroatom substituted allenes) with Lewis acids[3] or tran-
sition metals[4, 5] and also relying on an intramolecular version
that facilitates the reaction by virtue of entropic factors,[6]
have been developed. From a practical point of view aimed at
E-mail: tamaru@net.nagasaki-u.ac.jp
[b] Dr. T. Okajima
Department of Chemistry
Faculty of Culture and Education, Saga University
Honjo, Saga 840-8502 (Japan)
Supporting information for this article is available on the WWW under
http://www.chemeurj.org/ or from the author.
Chem. Eur. J. 2003, 9, 2419 2438
DOI: 10.1002/chem.200304586
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2419

Y. Tamaru et al.
FULL PAPER
the construction of the cyclobutane ring, ketene is the reagent
of choice since, owing to its polarized structure, ketene is
much more reactive than allene and readily reacts with many
formation of 6 11 is discussed on the basis of quantum
mechanical methods (RHF/3-21G* level).
The 4-vinylidene-2-oxazolidinones 2 are characteristic in
the bent structure of the allene bonds, where the Cb carbons
bend away from the N-sulfonyl group in the plane defined by
N-C4-C5, and the bond angles €C4-Ca-Cb significantly deviate
from linearity, from 172.5 176.08.[13]
ˆ
ˆ
types of double bonds (C C, C N, etc.) to form for example
cyclobutanones, b-lactams.[7]
In 1968, two contradicting reports appeared, one supporting
the concertedness of [2 ‡ 2] cycloaddition of allene and alkene
and the other not; Okamura et al.[8d] reported the concerted-
ness of the reactions of dimethyl maleate and fumarate with
1,1-dimethylallene, which proceeded in a stereospecific man-
ner. On the other hand, Dolbier et al.[9e] claimed that the [2 ‡
2] cycloaddition of [D2]allene and acrylonitrile proceeded via
stepwise processes (radical addition cyclization) on the basis
of secondary deuterium kinetic isotope effects.
ˆ
The allene p*(Ca Cb) orbital may lie low in energy owing to
ˆ
a through-space s*(N SO2) p*(Ca Cb) orbital interaction,
which brings about the allene bent bond (an attractive
ˆ
n (
)
p*(Ca Cb) charge transfer type interaction) as well
ˆ
SO
O
as the unique reactivity of 2.
In 1979, Pasto proposed an attractive idea that [2 ‡ 2]
cycloaddition might proceed concertedly by virtue of a
contribution of the cumulated orthogonal p-bond of allene
via a [(p2s ‡ p2s)allene ‡ p2s, alkene] process (see Figure 6).[10e] In
fact, however, despite extensive studies by himself[10] and
others,[2, 9, 11] the vast majority of results that have been
accumulated to date seems to point to a stepwise biradical
mechanism. Concertedness has been claimed sporadically in a
few reports with some limited number of examples.[8]
In this article, we would like to disclose for the first time
that the allene moiety of 4-vinylidene-2-oxazolidinones 2 is
surely able to undergo [2 ‡ 2] cycloaddition via a concerted
mechanism under mild, strictly thermal reaction conditions; 2
Results and Discussion
Preparation of 4-vinylidene-2-oxazolidinones 2: Bis-N-sul-
fonyl (1a c), bis-N-acyl (1d,e), and bis-N-phenyl (1 f)
biscarbamates of but-2-yn-1,4-diol were prepared quantita-
tively by treatment of the corresponding isocyanate
(2.2 equiv) and the diol in the presence of triethylamine
(2.2 equiv) in THF at 08C ! room temperature. Other bis-N-
tosyl biscarbamates involving unsymmetrical ones (1g r)
were also obtained in a similar way using the corresponding
but-2-yn-1,4-diols in quantitative yield. These biscarbamates,
except 1e, p, and r, form a nice crystalline solid (or powder)
and withstand storage for months in a refrigerator. Biscarba-
mates 1e, p, and r each appear as a heavy oil; purification by
means of column chromatography over silica gel and/or
crystallization from reaction mixtures all resulted in signifi-
cant loss owing to decomposition. Accordingly, these biscar-
bamates were prepared prior to use and used without
purification.
We planned preparation of 2 in expectation that the CuI ¥
Et3N catalytic system, developed by the authors for the
cyclization of propargyl carbamate to 4-methylene-2-oxazo-
lidinone,[14] might promote cyclization at the N atom of one of
the two carbamates of 1 in conjunction with elimination of the
other carbamate in an SN2' fashion. However, the expected
reaction did not take place; instead, only the cyclization
product 3 was produced in modest yield (run 6, Table 1).
Next, we examined palladium complexes as a catalyst
bearing in mind that oxidative addition of one of the two
carbamate moieties to the Pd0 species followed by extrusion
of p-toluenesulfonamide and carbon dioxide might form a
propargylpalladium I or an allenylpalladium intermediate II,
which would be reactive enough to undergo an intramolecular
displacement of Pd by the N anion of the other remaining
carbamate via either SN2' or reductive elimination, respec-
tively (Scheme 2).[12a] As was expected, all the palladium(0)
species examined turned out to serve as a catalyst for the
transformation of 1 to 2, though the efficiency largely
depended on the kind of palladium species (runs 3 5). The
phosphine-free [Pd2(dba)3] ¥ CHCl3 ¥ Et3N system was the
combination of choice, judging from the reaction temperature
and the yield of 2.
ˆ
reacts at the terminal Ca Cb bond with alkynes and alkenes of
a widely varying structural and electronic nature and gives rise
to methylenecyclobutenes 6 and methylenecyclobutanes 7 9,
respectively, in good to excellent yields by heating at 70
1008C(Scheme 1).[12]
With terminal alkynes and alkenes, the reactions are highly
regio- and stereoselective, delivering their unsaturated bonds
syn to the N-substituents of 2 and placing the substituents of
alkynes and alkenes at the 3-position of methylenecyclobu-
tenes and methylenecyclobutanes, respectively. Importantly,
alkenes react with 2 with complete retention of configuration
of their double bond geometries.
ˆ
Furthermore, the internal C4 Ca double bond of 2 partic-
ipates in [4 ‡ 2] and [3 ‡ 2] cycloaddition reactions toward
highly polarized enones and nitrile oxide and provides 10 and
11, respectively. Some enones provide 8 exclusively, while
some other enones furnish 10 selectively along with 8 as the
minor products. The mechanistic detail for the selective
Abstract in Japanese:
Remarkably, lowering the catalyst loading to 0.5 mol%
showed a significant increase in the yields (cf. runs 1 and 3,
Table 1). It should be noted that the use of a catalytic amount
2420
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
Table 1. Transition-metal catalyzed preparation of 4-vinylidene-2-oxazolidin-
to the elimination cyclization reaction of the other biscarba-
mates 1.
2-ones 2.[a]
O
Results for the elimination cyclization reaction of biscar-
bamates with various N-substituents, 1b f, are summarized in
Table 1. Bis-N-o-tosyl (1b), bis-N-methanesulfonyl (1c), and
bis-N-benzoyl biscarbamates (1d) reacted with similar ease,
and the reaction was completed within 12 h at room temper-
ature. Bis-N-a-methacryloyl biscarbamate (1e) was rather
reluctant and required over 2 d for completion of the reaction
(run 10). The expected product 2e was isolated in low yield
(14%). In addition to 2e, 4 (15%) was obtained in a
comparable amount. At an elevated temperature, only 4 was
produced in 33% yield (run 11). These results suggest that 2e
is a primary product and is labile under the conditions,
undergoing subsequent reactions, that is 1) aza-Claisen rear-
rangement, 2) imine enamine isomerization, and 3) cycliza-
tion and/or 1) intramolecular Michael addition of the enam-
ine moiety to enone and 2) hydrogen shift, to finally provide 4.
Bis-N-phenyl biscarbamate (1 f) was completely unreactive
and was recovered even by heating at 508C over 2 d (run 12).
In the presence of a stronger base, it decomposed (run 13).
These results clearly indicate that the ease of the conversion
of 1 to 2 depends on the acidity of carbamates.
Among 2a d, the allene carbamates 2a and b form a nice
stable crystalline solid, while 2c and d are a heavy oil and
partially decompose during purification by flash column
chromatography over silica gel and also during storage in a
refrigerator. Accordingly, 2c and d were prepared and used
promptly after purification by chromatography over silica gel
with a short column.
Table 2 summarizes the results for the cyclization of bis-N-
tosyl biscarbamates of 1-substituted but-2-yn-1,4-diols (1g
p). In these reactions, two regioisomers of products 2 and 5 are
•
ZHN
NHZ
O
metal catalyst
(1)
O
NZ
O
O
2
1
O
OCONHTs
O
O
NTs
O
N
O
3
4
O
Run
1
(Z)
Metal
(equiv)
Base
(equiv)
T/t[b] Product Yield
[%][c]
1
2
1a p-Ts
1a p-Ts
1a p-Ts
1a p-Ts
1a p-Ts
1a p-Ts
1b o-Ts
1c Ms
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
[Pd2(dba)3] ¥ CHCl3 none
(0.005)
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.1)
[Pd(PPh3)4]
(0.1)
[Pd(OAc)2]
(0.1)
CuCl
(0.1)
25/7
65/3
25/2
65/4
25/4
50/5
2a
2a
2a
2a
2a
3
73
0
3
44
45
3
(0.1)
Et3N
(0.1)
Et3N
(0.1)
Et3N
(0.1)
4
5
6
54
53
54
66
7
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
1e a-Met[d] [Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
1e a-Met[d] [Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
[Pd2(dba)3] ¥ CHCl3 Et3N
(0.005) (0.1)
[Pd2(dba)3] ¥ CHCl3 tBuOK 50/55 dec.[g]
(0.005) (0.1)
25/12 2b
25/12 2c
25/10 2d
8
9
1d Bz
10
11
12
13
25/47 2e
14[e]
15
33[e]
4
4
50/7
1 f Ph
1 f Ph
50/55
no rx[f]
Table 2. Preparation of 5-substituted 4-vinylideneoxazolidine-2-ones
[a] Reaction conditions: (1 mmol), transition-metal complex and base
1
2g p.[a]
(amount given) in dry THF (5 mL) under N2. [b] Temperature in8C and
reaction time in h. [c] Isolated yield for spectroscopically homogeneous
product. [d] a-Met ˆ a-methylacryloyl. [e] Overall yield based on but-2-yn-
1,4-diol. [f] Recovery of 1e. [g] Decomposition of 1 f.
O
2 TsHN
O
R
[Pd2(dba)3]•CHCl3
R1
(2)
(0.005 equiv)
THF
O
NHTs
R1
•
R2
1g-p
O
R2
•
R1
Pd
+
O
NTs
O
NTs
O
O
N
O
5g-p
Ts
2g-p
O
TsHN
NHTs
O
•
I
Pd0
O
Run
1
R1
R2
T [8C]/t [h]
% yield
2:5[b]
O
O
NTs
- TsNH2
- CO2
1
2
3
4
5
6
7
8
9
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
Me
Et
iPr
cHex
Ph
tBu
Me
(CH2)4
(CH2)5
2-adamantyl
H
H
H
H
H
H
Me
25/6
47
47
45
40
58
58
70
56
56
20[c]
2.1:1
1.7:1
2.5:1
2.5:1
2.1:1
2.1:1
30:1
O
•
O
1a
2a
25/56
50/24
60/20
25/11
40/25
25/13
25/4
O
O
Pd
N
Ts
II
Scheme 2. Palladium-catalyzed cyclization of biscarbamate 1.
20:1
21:1
25/6
60/23
10
2p only
of Et3N is essential to promote the reaction. In the absence of
Et3N, no trace amount of 2a was formed even under harsh
conditions; instead, 1a decomposed completely to give an
intractable mixture of products (run 2). Hereafter, we uni-
formly applied the conditions established in run 1 of Table 1
[a] Reaction conditions: 1 (1 mmol), [Pd2(dba)3] ¥ CHCl3 (0.005 mmol),
Et3N (0.1 mmol) in dry THF (5 mL) under N2. For runs 7 and 8, the
palladium catalyst in 0.02 mmol. [b] Non-separable mixture by means of
column chromatography over silica gel, the ratio being determined on the
1
basis of H NMR (400 MHz). [c] Overall yield based on but-2-yn-1,4-diol.
Chem. Eur. J. 2003, 9, 2419 2438
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2421

Y. Tamaru et al.
FULL PAPER
conceivable, depending on which one of the two carbamates
serves as a nitrogen nucleophile and the other as a leaving
group. Surprisingly, the regioselectivity of the cyclization of
1-monosubstituted biscarbamates 1g l was almost independ-
ent of the steric bulkand the electronic nature of the
substituents, and mixtures of 2 and 5 were obtained in a ratio
of about 2:1. On the other hand, 1,1-geminally disubstituted
biscarbamates 1m p underwent cyclization to provide 2
almost exclusively. The regioselectivity may be attributed to
0
À
steric hindrance of oxidative addition of the C1 O bond to Pd
as well as to the Breseley Ingold Thorpe effects[15] (but-
tressing effects) of the C1 substituents that make the nitrogen
atom of C1 carbamate and the C2 carbon come close to each
other.
Equations (3) and (4) demonstrate that the present Pd-
catalyzed cyclization is applicable not only to highly substi-
tuted biscarbamates, but also to biscarbamates with a variety
of electron-withdrawing substituents on the nitrogen atom.
The products 2q and 2r form a nice crystalline solid. It should
Figure 1. Chem 3D drawing of X-ray structure of 4-vinylidene-2-oxazoli-
À
dinones 2, placing C4-Ca Cb atoms in an xy plane. One of the sulfonyl
oxygens points to Ca and forms a loose planar five-membered ring. For
clarity, all hydrogens are omitted.
O
TsHN
O
•
[Pd2(dba)3]•CHCl3
(3)
(0.005 equiv)
Et3N (0.1 equiv)
THF, 25 °C, 16 h
O
NHTs
1q
O
NTs
O
O
2q (59%)
O
Cl3CH2CO3SNH
O
[Pd2(dba)3]•CHCl3
(4)
O
NHSO3CH2CCl3
(0.005 equiv)
Et3N (0.1 equiv)
THF, 25 °C, 16 h
O
1r
•
O
O
NSO3CH2CCl3
2r
(28% overall based on
1,1-dimethyl-2-butyn-1,4-diol)
Figure 2. Chem 3D Drawing of X-ray structure of 4-vinylidene-2-oxazo-
lidinones 2, placing C5-C4-Ca atoms in an xz plane. Except the one of 2p, all
Cb reside in the C5-C4-Ca plane. For clarity, all hydrogens are omitted, and
tolyl is replaced by Me.
be noted that 2r was obtained in 28% overall yield based on
1,1-dimethylbut-2-yn-1,4-diol in three-step assembly-line op-
erations without purification of the intermediates: moisture
and thermal-sensitive 2,2,2-trichloroethoxysulfonyl isocya-
nate[16] and biscarbamate 1r with a propensity to readily
undergo polymerization.
repulsion between one of the adamantyl methylene groups
(indicated by an arrow) and the allene Cb. In fact, as is seen by
ˆ
ˆ
a close examination of Figure 2, the C4 Ca Cb allene bond of
2p deviates from linearity and the Cb carbon is located out of
the C4-C5-Ca plane, though the Cb carbons of the other 2
compounds all reside on the plane. Second, either one of the
two oxygen atoms (O3) of the sulfonyl group points to the
allene central carbon, Ca, and seems to form a loose, planar
five-membered ring composed of Ca, C4, N, S, and O3, as if
there exists an attractive interaction between them (Figure 1).
Structure of 4-vinylidene-2-oxazolidinones 2 characterized by
the bent allene bond: Figures 1 and 2 list the Chem 3D
presentation of the structure of allene carbamates 2 of
interest, determined by single-crystal X-ray diffraction meth-
ods. The dihedral angles, bond angles and lengths of interest
for all 2 determined by X-ray analyses are compiled in
Table 3.[17, 18] The X-ray crystallographic analyses have re-
vealed that all of the oxazolidinones 2 possess common but
unique structural features.
À
The O3 Ca distances are in the range of 2.82 2.87 ä and are
shorter than the sum of van der Waals radii of O (1.75 ä) and
C (1.70 ä).[19] This feature may be inherent in allene
carbamates 2, and may not be due to crystal packing effects
since, as is seen in Figure 1, the p-tolyl and o-tolyl groups take
a variety of conformations in the crystals. Furthermore, this
arrangement seems to be a general feature of all 2 and not
First, the 2-oxazolidinone ring of 2 is almost planar, except
that of 2p (Figure 2). For this particular compound, the
deformation of the oxazolidinone ring may be caused by steric
2422
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
Table 4. Allene bond angles [8] of 4-vinylidene-2-oxazolidinones calculated at
RHF/3-21G(*). Values in parentheses were determined by X-ray crystallo-
graphic analyses.
affected by the space requirements of the C5 and/or Cb
ˆ
ˆ
substituents. Finally, and most importantly, the C4 Ca Cb
allene bonds significantly deviate from linearity away from
the sulfonyl groups, forming the bond angles between 173
1768 (Figure 1 and Table 3), where the Cb carbons reside
almost in the plane defined by N-C4-Ca (cf., dihedral angles,
€N-C4-Ca-Cb and €C5-C4-Ca-Cb Table 3) even for the mole-
cules that possess sterically bulky substituents at the C5
position (e.g., 2n, 2q).
À
À
À
N H N Me N SO2Me N-SO2-o-Tol
N-SO2-p-Tol
C5 H,H
C5 H,Me
178.9 178.5
174.8
174.0 (174.5) 175.0 (172.5)
174.9 (175.3)
C5 Me,Me 178.8 178.4
C5 (CH2)4 179.0 178.5
174.9
174.9
175.2 (176.0)
175.0 (172.4)
This is, to the best of our knowledge, the first example
which demonstrates that the allene bond deviates from
linearity in the absence of any steric factors (e.g., ring strain,
torsional strain and/or packing effects).[13, 20]
In order to address the reason why 2 take such an
unfavorable configuration and conformation on steric
grounds, we examined the quantum mechanical calculations.
The RHF/3-21G* optimized parameters for the atomic angles
for the allene bond of 4-vinylidene-2-oxazolidinones with H,
Me, SO2Me, SO2-o-Tol, and SO2-p-Tol substituents on the
nitrogen atom are listed in Table 4, together with the angles
determined by X-ray studies (in parentheses). The results
indicate that a clear-cut discrepancy does exist in the
optimized bond angles between N-H, -Me derivatives and
N-sulfonyl derivatives; the N-H and N-Me derivatives are the
most stable with an almost linear allene bond, irrespective of
the C5 substituents while, in good accord with the experimen-
tal results, N-sulfonyl derivatives take uniformly a bent allene
bond. The amount of the bending angle determined by
calculation is about 58.
Figure 3. Population analyses of 2c based on MSK scheme.
evaluated at Becke3LYP/6-31‡G*//RHF/3-21G*) for the
simplest allene carbamate 2c. For the most stable parallel
conformer a) the oxygen atom, pointing to Ca, carries a
considerable amount of negative charge (À0.45), which is
The population analysis based on the Merz Kollman
scheme (MSK) in shown in Figure 3; the values were
Table 3. Selected bond and dihedral angles [8] and bond lengths [ä] of 4-vinylidene-2-oxazolidinones 2.
β
R
•
α
O3
4
5
1
O
N
S
2
O4
Me
O
2
2a
2b
2g
2k
angles
2m
2n
2p
2q
C4-Ca-Cb
N-C4-Ca
C5-C4-Ca
N-C4-C5
C2-N-C4
C2-N-S
172.5
128.7
126.8
104.5
109.0
122.0
125.0
31.0
174.5
175.3
129.5
125.9
104.5
109.0
123.0
124.7
31.8
173.6
176.0
172.4
175.0
125.8
130.4
103.7
109.8
122.0
127.5
À 16.6
À 16.0
81.5
À 102.8
173.5
129.8
125.6
104.5
111.0
121.0
126.9
À 6.8
11.9
129.2
127.0
103.8
110.5
121.5
127.8
2.9
130.4
126.3
103.3
112.2
120.5
127.3
6.7
13.9
164.5
14.6
129.5
126.2
104.3
110.0
122.3
125.4
25.2
À 0.5
166.3
À 12.6
129.5
126.0
104.5
111.0
119.7
125.3
20.4
À 28.3
174.6
À 8.8
S-N-C4
O3-S-N-C4
S-N-C4-Ca
N-C4-Ca-Cb
C5-C4-Ca-Cb
À 14.2
À 163.0
15.3
10.2
À 15.0
À 147.5
28.5
À 176.9
180.0
2.0
5.7
bond lengths
1.479
À
O1 C2
1.334
1.338
1.318
1.413
1.429
1.496
1.431
1.291
1.292
1.191
1.687
2.837
1.337
1.338
1.341
1.333
À
C2
N
1.398
1.434
1.487
1.435
1.296
1.283
1.195
1.683
2.854
1.394
1.435
1.500
1.431
1.295
1.297
1.192
1.673
2.829
1.396
1.406
1.497
1.402
1.276
1.285
1.193
1.711
1.400
1.432
1.520
1.466
1.298
1.293
1.193
1.680
2.845
1.396
1.437
1.523
1.470
1.286
1.290
1.202
1.686
2.834
1.398
1.433
1.521
1.486
1.300
1.293
1.194
1.681
2.867
1.391
1.431
1.519
1.462
1.294
1.302
1.195
1.678
2.817
À
N C4
À
C4 C5
À
C5 O1
À
C4 Ca
À
Ca Cb
À
C2 O2
À
N S
Ca ¥¥¥ O3
2.852
Chem. Eur. J. 2003, 9, 2419 2438
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2423

Y. Tamaru et al.
FULL PAPER
8.2
apparently less than that of the other oxygen atom (À0.47).
The bisect b) and orthogonal c) conformers are higher in
energy by 4.3 and 5.1 kcalmolÀ1, respectively, as compared
with the parallel conformer a). From the results of the
calculations we conclude that the stability of the bent bond
structure of allenes 2 of the parallel conformer a) is brought
about by a charge transfer type interaction between the
H
N
4.4
CO2Me
H
H
4.0
H
Ph
H
10.0
6.4
H
H
H
H
H
6.5
O
SO2
O
N
H
SO2
H
O
O
(Z)-6b
ˆ
ˆ
oxygen of the parallel S O bond and the Ca Cb double bond,
(Z)-6a
3.0
Hd
ˆ
that is, an nO p*(Ca Cb) interaction. This n p* interaction
12.1
4.5
ˆ
may be substantiated by the low-lying LUMO (Ca Cb), which
Hd Ph
Hc Ph
13.8
1,5
2.3
ˆ
might be caused by p*(Ca Cb) À s*(N-SO2) interaction.
He
Ha
Hc
Et
1.4
3.8
4.6
These orbitals are aligned parallel in close proximity to each
other and might be able to interact through space effectively.
D
Hb
N
Ha
O
3.5
O
N
SO2
H
SO2
H
O
O
Concerted thermal [2 ‡ 2] cycloaddition of 2 at the terminal
ˆ
Ca Cb bonds with alkynes, alkenes, and dienes: When 2a was
7c
[D1]-(Z,E)-7h
heated in an excess amount of phenylacetylene at 1008C for
4 h, a spot of 2a (Rf ˆ 0.45, hexane/AcOEt 2:1 v/v) disap-
peared completely and a new spot (Rf ˆ 0.55) appeared on the
1
Figure 4. NOE increment (%) determined by H NMR (400 MHz).
1
TLC [Eq. (5)]. The H NMR spectrum of the crude reaction
mixture measured after removal of excess phenylacetylene
under reduced pressure revealed that product 6a was
composed of a single isomer, which decomposed gradually
in an NMR tube upon standing for several hours at room
temperature. Crystallization from dichloromethane/hexane
provided 6a as a fine colorless solid, which also partially
decomposed and the color turned brown even in a refrigerator
within a few days.
Encouraged with the unique and unprecedented reactivity
of the allene bond of 2 toward alkynes, we next examined
extensively the reaction with alkenes of a wide structural and
electronic variety. The results are summarized in Table 5. In
general, alkenes bearing conjugated p-systems (e.g., styrenes
and dienes) and electron-withdrawing groups showed parallel
results. The results for the reactions with dienes are summar-
ized separately in Table 6.
Of the two conceivable stereoisomers, we first expected the
structure of 6a to be (E)-6a, simply because of the easier
access of acetylene to 2a from the less crowded side of the
allene bond, being distal from the N-sulfonyl group. Surpris-
ingly, however, NOE experiments of the product indicated
Alkenes bearing electron-donating substituents (e.g., enol
ethers,[22] allylsilanes)[23] displayed a completely different
reactivity [Eq. (6)]. They induced 1,3-sulfonyl migration and
provided tetrahydropyridines formed by a formal [4 ‡ 2]
cycloaddition reaction. This type of reactivity of 2 is general
toward a variety of other nucleophiles, encompassing alco-
hols, silanes (SSiH), indoles; the results will be reported
elsewhere in due course. Simple alkenes, such as 1-decene and
3-phenyl-1-propene, were unreactive and 2 were recovered in
almost all cases.
Ph
•
100 °C, 4 h
Ph
+
(5)
O
NTs
O
NTs
(Z)-6a (61%)
25 equiv
2a
O
Ph
O
Ts
•
100 °C, 36 h
O
NTs
(E)-6a (0%)
OMe
+
(6)
O
N
O
N
Ts
dioxane
O
OMe
86 %
O
2a
O
that 6a should in fact be (Z)-6a (Figure 4). The reproduci-
bility of the experiment was confirmed by three individual
runs. Each time, the absence of (E)-6a was confirmed by close
In contrast to the instability of methylenecyclobutenes 6,
methylenecyclobutanes, 7 and 8, were stable and could be
readily purified by means of column chromatography over
silica gel and/or, in some instances, direct crystallization from
the reaction mixtures. As might be apparent from Table 5, no
discernible differences in reactivity among 2 were observed,
although they differed in the N-substituents and the C5
substituents. Adamantane derivative 2p was one exception,
which was totally unreactive and was recovered quantitatively
by exposure to styrene and acrylonitrile under usual and even
somewhat harsh conditions (1008C for 10 h). The adamantyl
group may sterically protect the allene bond from an attackof
these alkenes.
1
scrutiny of the H NMR spectra (400 MHz).
In order to confirm this unexpected high stereoselectivity,
we next examined ethyl propiolate as an alkyne of different
electronic nature under similar reaction conditions (run 1,
Table 5). To our pleasant surprise, the reaction proceeded
much smoother and was completed within 4 h at 808C, giving
rise to (Z)-6b as a single isomer. The methylenecyclobutene
product (Z)-6b (m.p. 66.0 66.58C from CH2Cl2/hexane)
again turned out to be rather unstable especially in a solution
under air; the color gradually turned brown or black-
brown.[21]
2424
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
Table 5. Thermal [2 ‡ 2] cycloaddition of 2 with alkynes and alkenes.[a]
Among the data in Table 5, the selective reaction of
2-methylbut-1-en-3-yne at the double bond, giving rise to 7 f
(run 13) and a quantitative formation of 8g by the reaction
with methyl a-siloxyacrylate are especially impressive
(run 15). These results along with the reaction with a-
(trimethylsiloxy)styrene (run 12) demonstrate that the pres-
ent [2 ‡ 2] cycloaddition is highly tolerant of a wide range of
alkenes with different electronic nature; this is in sharp
contrast to the reaction pattern displayed by simple electron-
rich alkenes [Eq. (6)].
Run Allene 2
Alkene
or alkyne
T [8C]/ Product
t [h] (%isolated yield)
1
80/4
2
3
2a
2a
100/22
80/22
Interestingly, however, the reaction is tolerant only of
terminal alkenes and alkynes. Internal alkenes, such as methyl
b-methylacrylate, b-methylacrylonitrile, b-phenylacryloni-
trile, 2-cyclohexenone, dimethylmaleate, and internal alkynes,
such as dimethyl acetylenedicarboxylate and diphenylacety-
lene, were all unreactive and resulted in a recovery (or slight
decomposition) of 2 under usual reaction conditions. All
attempts employing higher temperature and longer reaction
time (e.g., 1208C for 1 d) resulted only in the decomposition
of 2.
4
5
6
2a
2a
2a
80/17
80/10
80/22
The decisively low reactivity of internal alkenes might be
rationalized by assuming that the alkenes would react with 2
in similar way to alkynes and the allylic methylenes of the
cyclobutane ring syn to N-Ts might be delivered from the
alkene terminal carbons. The methylene groups of 7 and 8 syn
to N-Ts suffer from allylic strain against the N-Ts group.
Therefore, there is not enough room to accommodate
substituents on the methylene carbon.
7
80/23
8
9
2d
2d
80/46
80/22
In fact, this proved to be the case. In order to clarify the
stereochemical course of the [2 ‡ 2] cycloaddition reaction,
commercial [D8]styrene was used as a probe [Eq. (7) and (8)].
10
11
12
100/5
80/48
80/48
1
The 400 MHz H NMR spectrum of the cyclobutane part of
the product [D8]-7c (b) is shown in Figure 5 along with that of
7c (a) for comparison. Fortunately, all the methylene protons
and the methyne proton of 7c appeared separately and could
be assigned unequivocally as indicated in Figure 5a on the
basis of NOE experiments (Figure 4).
2m
2m
Comparison of Figure 5a and b clearly indicates that [D8]-
7c is composed of a single stereoisomer and possesses a (Z)-
structure, since the methylene protons syn to the tosyl group,
Hb and Hc, of 7c disappear completely and the methylene
protons anti to the tosyl group, Hd and He, remain and appear
as a pair of doublets. The absence of a pair of doublets
ascribable to Hb and Hc of the other stereoisomer, (E)-[D8]-
7c, indicates that the degree of stereoselectivity is more than
97% (a limit of 1H NMR detection). The reaction of 2a with
[D8]styrene showed completely parallel results [Eq. (7)],
though the 1H NMR spectra of 7a and (Z)-[D8]-7a appeared
not as simple as those of 7c and [D8]-7c owing to a long-range
coupling with the C5 methylene protons.[21]
Parallel results were obtained for the reactions of 2a with
[D5]-a-methylacrylonitrile [97% atom D, Eq. (9)] and 2m
with b,b-dideuterio-a-(trimethylsiloxy)styrene [96% atom D,
Eq. (10)], where [D5]-(Z)-8c and [D2]-(Z)-7e, respectively,
were produced exclusively.[21] The results given in Equa-
tions (7) (10) clearly indicate that the allylic methylene
groups of methylenecyclobutanes syn to the N-Ts group
originate from the terminal sp2 carbons of alkenes, irrespec-
tive of the stereoelectronic nature of the substituents.
13
2m
80/120
14
15
2m
2m
80/17
100/8
16
17
80/13
80/10
[a] Unless otherwise specified, 2 (0.5 mmol) and alkyne or alkene (4.0 mL,
30 60 mmol) were heated under N2. [b] 2 (0.5 mmol) and alkene
(5.0 mmol) were heated under N2. [c] 2 (0.5 mmol) and alkene (10.0 mmol)
in dioxane (1.0 mL) were heated in a sealed tube under N2. [d] 2 (0.5 mmol)
and an alkene (10.0 mmol) were heated under N2.
Chem. Eur. J. 2003, 9, 2419 2438
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2425

Y. Tamaru et al.
FULL PAPER
OTMS
Ph
D
OTMS
Ph
80 °C, 12 h
D
+
(10)
2m
D
O
NTs
D
10 equiv
[D2]-(Z)-7e (74%)
O
In order to shed more light on the stereochemical course,
we next examined the reaction of 2a and 2m with cis-b-
monodeuteriostyrene (96% atom D) [Eq. (11) and (12)], and
we were gratified to find that these reactions proceeded with
complete retention of configuration of the double bond
(Figure 5c).[24] Disappearance of the resonance of Hb, no
change in the coupling pattern of Hd, coalescing of the
resonance of He from a ddt to a ddd, and a change in the
absorption of Hc from a ddt to a broad doublet, all combine to
indicate the substitution of D for Hb.
Ph
H
H
100 °C, 6 h
Ph
20 equiv
(11)
+
2a
D
NTs
D
O
[D1]-(Z)-cis-7a (68%)
O
Ph
H
H
100 °C, 28 h
Ph
20 equiv
(12)
2m
+
D
D
O
NTs
O
[D1]-(Z)-cis-7c (90%)
Furthermore, stereochemically defined trisubstituted al-
kene, (E)-a-ethyl-b-monodeuteriostyrene [90% atom D,
Eq. (13)], was subjected to the reaction. Figure 5d and the
Ph
Et
D
Et
100 °C, 28 h
(13)
+
2m
Figure 5. 1H NMR spectra (400 MHz) of the cyclobutane moieties of 7c
(a), (Z)-[D8]-7c (b), (Z)-cis-[D1]-7c (c), and (Z,E)-[D1]-7h (d). In (d), the
small peaks, Hb' and Hc', are due to [D0]-a-ethylstyrene.
D
H
Ph
20 equiv
O
NTs
O
[D1]-(Z,E)-7h (90%)
C6D5
D
NOE data in Figure 4 clearly indicate that the reaction
proceeds stereoselectively and the selectivity is more than
•
D
D
100 °C, 10 h
D
+
(7)
D
C6D5
16 equiv
O
NTs
1
97% (a limit of H NMR detection).[24] The product (Z,E)-
O
NTs
D
2a
O
[D8]-(Z)-7a (80%)
[D1]-7h is Z with respect to the exocyclic double bond and E
with respect to the substituents of the cyclobutane ring. The
spectrum is contaminated by small peaks Hb' (brd) and Hc'
(dt), which are apparently attributed to the product formed by
the reaction with non-deuterated a-ethylstyrene (10%)
present in the starting material as a contaminant.
Allenes are good reaction partners in the Diels Alder
reaction and serve as reactive dienophiles.[25, 26] The internal
allene double bonds of vinylallenes form a 4p-system in
conjunction with the vinyl groups and, in turn, they serve as
reactive dienes toward a variety of dienophiles.[26a, 27] In sharp
contrast, the allene of 2 displayed no dienophilic reactivity
toward a variety of dienes, but instead, selectively underwent
[2 ‡ 2] cycloaddition to provide 3-vinyl-1-methylenecyclobu-
O
C6D5
D
•
D
D
100 °C, 10 h
D
+
(8)
D
C6D5
O
NTs
O
NTs
[D8]-(Z)-7c (80%)
D
2m
O
50 equiv
O
CD3
CN
D
CD3
CN
80 °C, 16 h
D
+
(9)
2a
D
O
NTs
D
[D5]-(Z)-8c (58%)
20 equiv
O
2426
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
tanes 9 in good to excellent yields (Table 6).[6, 28] Furthermore,
in general, the [2 ‡ 2] cycloaddition of 2 with dienes pro-
ceeded much easier than that with alkenes and alkynes. This
may be apparent by comparing the reaction conditions shown
in Tables 5 and 6; for the reaction with dienes, in most cases,
10 equivalents or less of dienes (runs 4 and 12) were used. In
addition, the reactions proceeded smoothly even as a diluted
solution in dioxane. Dioxane was used uniformly as a solvent
in order to avoid the loss of dienes by evaporation.
The exclusive [2 ‡ 2] preference over [4 ‡ 2] cycloaddition
associated with 2 is quite remarkable taking into consider-
ation the fact that [2 ‡ 2] cycloaddition of allenes and dienes
has been reported sporadically only for a limited number of
intramolecular reactions, where allenes and dienes are
designed deliberately to undergo [4 ‡ 2] cycloaddition under
great difficulty.[29]
Table 6. Thermal [2 ‡ 2] cycloaddition of 2 with 1,3-dienes.[a]
Run Allene
1,3-Diene
T [8C]/ Product
t [h]
(% isolated product)
1
70/44
A general trend has been observed for the regioselectivity
of dienes; one of the two double bonds undergoes reaction
selectively; 1) 1-substituted dienes react at the distal non-
substituted 3,4-double bonds (e.g., runs 3 and 9, Table 6), 2) 2-
substituted dienes react selectively at the 1,2-double bonds
irrespective of the electronic nature of the substituents (e.g.,
runs 2, 6, and 11), and 3) unsymmetrically 2,3-disubstituted
dienes react selectively at the double bonds with higher
electron density (run 13). For example, although both the
methyl and triisopropylsilyloxy groups of 2-methyl-3-triiso-
propylsiloxy-1,3-butadiene are electron-donating, the latter is
by far more powerful in the ability; hence, this diene reacted
2
3
4
2a
2a
2a
80/36
80/9
80/22
À
exclusively at the C3 C4 double bond and provided 9m as a
single product (run 13).
5
70/91
It should be noted that dienes bearing siloxy substituents
either at the 1- or at the 2-position (runs 4, 9, and 13), like a-
siloxystyrene [run 12, Table 5 and Eq. (10)], all undergo [2 ‡
2] cycloaddition, which is in contrast to the reaction behavior
that simple vinyl ethers display [Eq. (6)].[22] The geometry of
dienes was retained completely in the products, that is, trans
dienes provided 3-(trans-1-alkenyl)methylenecyclobutanes
(e.g., runs 3, 4, and 8 10) and cis-dienes 3-(cis-1-alkenyl)me-
thylenecyclobutanes exclusively [Eq. (14)]. A mixture of cis-
and trans-5-trimethylsilyl-1,3-pentadiene (E:Z 1.0:3.6) pro-
vided 9o as a single isomer in excellent yield. Interestingly, the
reaction with a trans-enriched mixture (E:Z 4:1, obtained by
isomerization of the cis-rich mixture by catalytic amounts of
phenylmercaptane/azobisisobutyronitrile (AIBN), benzene
reflux) was very slow and provided 9o in 45% isolated yield
with recovery of 2m in 30% yield under the same reaction
conditions as Equation (14) (96 h). These results indicate that
only cis-5-trimethylsilyl-1,3-pentadiene participates in these
reactions and provide 9o with retention of configuration of
the double bond.
6
7
8
2m
2m
2m
80/10
80/42
80/22
9
2m
2m
80/22
80/29
10
11
12
13
2m
2m
2m
80/42
80/22
80 °C, 35 h
SiMe3
2m
+
SiMe3
dioxane (1 mL)
O
N
Ts
(14)
5 mmol
(E:Z = 1:3.6)
0.5 mmol
O
100/37
9o (97 %)
As was observed for internal alkynes and alkenes and in
good accord with 1), described above, internal dienes, such as
1,3-cyclohexadiene and 1,3-cyclopentadiene, were also un-
reactive and no expected products were obtained at all.
The mechanistic details associated with the thermal [2 ‡ 2]
cycloaddition (either concerted or stepwise) constitute a topic
of much study and debate. Most studies, evidenced by the
14
80/45
[a] Unless otherwise specified, 2 (0.5 mmol) and diene (5.0 mmol) in
dioxane (0.5 mL) were heated under N2. [b] 2 (0.5 mmol) and diene
(20 mmol) in dioxane (1.5 mL) were heated under N2. [c] 2 (0.5 mmol) and
a diene (2.0 mmol) in dioxane (0.5 mL) were heated under N2.
Chem. Eur. J. 2003, 9, 2419 2438
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2427

Y. Tamaru et al.
FULL PAPER
11, 26, 27]
regio- and stereochemical outcomes[6, 9
and H/D
isotope effects,[9e] seem to strongly favor a stepwise biradical
mechanism. In sharp contrast to this, all experimental results
obtained for the [2 ‡ 2] addition of 2 with a wide variety of
alkynes, alkenes and 1,3-dienes presented here seem to point
to a concerted mechanism involving a six-electron H¸ckel
[(p2s‡p2s)allene ‡ p2s] transition state, proposed by Pasto[10e] and
predicted by Fukui et al. based on the frontier orbital theory
(Figure 6).[30]
Figure 7. RHF/3-21G* transition structures leading to 8b (a) and 8k (b)
with SO2Me in place of SO2-p-Tol. For clarity, all hydrogens except the
hydrogens on the reaction centers were omitted. For further discussion of
the TS structure b) leading 8k, see next Section.
quantum mechanical methods for the concerted [2 ‡ 2] cyclo-
addition of ketene and ethylene;[7l] the single bonds between
the Ca and the alkene C2 are almost fully formed (1.70
À
1.71 ä). The other incipient carbon carbon bonds, between
Cb and the alkene C1, are much longer (2.65 2.73 ä). The C1
carbons are in fact much closer to the Ca in the transition
states (2.37 2.39 ä) than to the Cb to which they will be
bonded in the products.
Concerted thermal [4 ‡ 2] and [3 ‡ 2] cycloadditions of 2 at
the internal double bonds with enones and nitrile oxides: In
contrast to the fact that electron-deficient alkenes, such as
acrylonitrile, acrylamide, and ethyl acrylate, selectively under-
Figure 6. Possible explanation for a thermal, concerted [2 ‡ 2] cycloaddi-
tion based on ™the orbital interaction in three-systems∫.[30] a) Reactions for
electron-deficient alkenes and alkynes. b) Reactions for electron-rich and
conjugated alkenes and alkynes.
ˆ
went [2 ‡ 2] cycloaddition toward 2 at the terminal Ca Cb
bonds (Table 5), a similarly electron-deficient ketone, methyl
vinyl ketone, displayed completely different reactivity; this
ˆ
ketone selectively reacted with 2n at the internal C4 Ca bond,
The unique reactivity associated with 2 might be primarily
giving rise to a spiro compound, 10a, as the major product
along with a [2 ‡ 2] cycloaddition product 8i as the minor
product (run 1, Table 7). Other enones that display this
inverse electron demand [4 ‡ 2] cycloaddition reactivity[31]
are summarized in Table 7.[32]
ˆ
attributed to a strong s*(N SO2) À p*(Ca Cb) interaction of
ˆ
2a,m,o,r (or s*(N CO) À p*(Ca Cb) interaction for 2d),
ˆ
which causes 1) the lowering of the p*(Ca Cb) energy level
(and hence, lowering of the activation energy for the [2 ‡ 2]
ˆ
addition) and 2) the rehybridization of the p*(Ca Cb) orbitals
The common structural feature of electron-deficient al-
kenes that show [4 ‡ 2] reactivity is that they are all a,b-
unsaturated aldehydes and ketones. Judging from the reaction
conditions (temperature, time, and equivalency of enones
relative to 2), the enones are more reactive than the electron-
deficient alkenes listed in Table 5. The ratio of 10 to 8 largely
depends on the kind of enones, ranging from 80:18 (%
isolated yield, run 1) for methyl vinyl ketone to 11:83 (run 4)
for a-methylacrolein.
(sp3-like, and hence, better overlap between the p orbitals of
alkene C1 and allene Cb in the opposite face to N-Ts). As is
illustrated in Figure 6a for electron-deficient alkynes and
alkenes and in Figure 6b for electron-rich and conjugated
alkynes and alkenes, the three-system interaction,[30] with a
coaxial overlap of the p orbitals of Ca and C2 and a
perpendicular overlap of the p orbitals of Cb and C1,
necessitates a 908 counter-clockwise rotation of the oxazoli-
dinone ring (i.e., a rotation of the N-Ts group toward C2) to
furnish (Z)-6 9.
Before discussing the product ratios in detail, it should be
clarified whether the ratios are due to either kinetic or
The mechanism proposed here was supported by the RHF/
3-21G* concerted transition-state structures and the geo-
metrical transformation along the intrinsic reaction coordi-
nate for the reaction of 2a (SO2Me in place of SO2Tol) with
acrylonitrile (Figure 7a) and methyl a-methylvinyl ketone
(Figure 7b). An alternative coaxial approach of the p orbitals
of Cb and C1, accompanied with perpendicular interaction
between the p orbitals of Ca and C2, could hardly be
reconciled with the reactivity observed for 2m and 2n, since
the bulky C5 substituents of these allenes would render this
mode of approach sterically unfavorable.
À
thermodynamic control, because the cyclobutane C C bonds
À
of 8i l and the dihydropyran C O bonds of 10a d [indicated
with a dotted line, Eq. (15)] are expected to be prone to
undergo heterolytic cleavage, giving rise to zwitterionic
intermediates III (a pair of ‡/ À ) characterized by the
carbanions stabilized by aldehyde or ketone and the allylic
O
-/•
COMe
+/•
O
(15)
O
N
Ts
O
N
O
N
Ts
Ts
8k
The transition-state structures a) and b) in Figure 7 are
apparently asynchronous and similar to the one located by
O
10c
III
O
O
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
Table 7. Concomitant thermal [4 ‡ 2] and [2 ‡ 2] cycloaddition reaction of
enones with 2n.
the methyl group at the a-position of the vinyl group
decreases a positive charge on the terminal CH2 carbon. As
a consequence, these two methyl groups offset their electronic
effects, giving rise to a mixture of 10c and 8k in almost the
same amounts (run 3).
[c]
Run Enone t[a]
Yield [%] of 10 and 8[b]
10
Eact
[h]
8
10
8
In order to test the feasibility of this explanation, the
reaction of run 3 was examined in polar solvents in expect-
ation that in such solvents a transition state leading to 10c
involving such polarized enone as a reaction partner might be
stabilized and 10c would be formed in a higher proportion.
However, on the contrary, 10c was obtained in significantly
lesser amounts in polar solvents: 10c and 8k in 9 and 78%
yields in ethanol (61 h at reflux) and 23 and 70% yields in
DMSO (38 h at 808C), respectively.
In order to rationalize these unexpected results, pathways
leading to 8 and 10 were analyzed with quantum mechanical
methods using GAUSSIAN 98 program[34] with density func-
tional theory (DFT).[35] Relative activation energies (Eact),
investigated at the Becke3LYP/6-31G* level based on the
RHF/3-21G* optimized geometries, are tabulated in Table 7;
the reaction with acrolein was set as a standard (run 2).
Figure 9 shows two pairs of TSs leading to 8j (a) and 10b
(b) (reaction with acrolein) and 8k (c) and 10c (d) (reaction
with methyl a-methylvinyl ketone) that are located utilizing a
gradient method without any geometrical constraint at the
RHF/3-21G* basis set.
1
2
2
6
À 3.0 3.4
0.0 0.0
3
4
14
10
9.3 7.3
12.7 2.7
[a] Allene 2n and enone (20 equiv) were heated at 808C under N2.
[b] Yields refer to the isolated materials by means of column chromatog-
raphy over silica gel. [c] Relative activation energies [kJmolÀ1] for TSs
leading to 10 and 8 calculated at the Becke3LYP/6-31G* level based on the
RHF/3-21G* optimized geometries (the reaction with acrolein as
standard).
a
carbocations stabilized by the nitrogen atom.[28a] These bonds
are also subject to homolytic cleavage, giving rise to biradical
* *
intermediates III (a pair of / ). Accordingly, we examined a
set of thermal isomerization experiments, that is, heating of
pure, isolated 8k and 10c separately at 808C for 68 h using
20 equivalents of methyl a-methylvinyl ketone as a solvent.
The results were clear-cut and no isomerization between them
tookplace at all, that is, 8k and 10c were recovered
quantitatively, indicating that the product distributions listed
in Table 7 are the ones controlled kinetically.
It is worth noting that the behavior of 2 is in sharp contrast
to that of N-allenyl-2-oxazolidinones of close structural
similarity, reported recently by Hsung et al.,[33] which exclu-
sively undergo inverse electron demand [4 ‡ 2] cycloaddition
upon exposure to a variety of enones and enals, including
methyl vinyl ketone and acrolein.
Figure 9. RHF/3-21G* transition structures leading to 8j (a), 10b (b),
8k (c), and 10c (d) with SO2Me in place of SO2-p-Tol. For clarity, all
hydrogens of 2n except for the hydrogens on Cb are omitted.
The product distribution in Table 7 may be rationalized
qualitatively by supposing that the substituents R1 and R2
(Figure 8) that are capable of increasing a negative charge on
the oxygen and a positive charge on the terminal CH2,
respectively, would promote [4 ‡ 2] cycloaddition. For exam-
ple, the methyl group of methyl vinyl ketone increases the
electron density on the O atom and promotes the inverse
electron demand hetero Diels Alder reaction (run 1, Ta-
ble 7), while the methyl group of a-methacrolein decreases a
positive charge on the terminal CH2 and retards the hetero
Diels Alder reaction (run 4).
The activation energy for inverse electron demand [4 ‡ 2]
addition (Eact, [4 ‡ 2]) changes as expected qualitatively (see
above), and increases gradually in the order of run 1 to 4. On
the other hand, the activation energy for [2 ‡ 2] addition (Eact
,
[2 ‡ 2]) scarcely depends on the electronic nature of enones; a
part (3 4 kJmolÀ1) of the large Eact, [2 ‡ 2] (as well as the
Eact, [4 ‡ 2] in run 3 may be attributed to steric repulsion
between the eclipsed methyl groups indicated by double-
headed curved arrow in Figure 9c and d.
Of the two methyl groups of
Interestingly, all TSs leading to 8i l turned out to possess
s-cis conformation with respect to the enone double bond and
carbonyl, although the corresponding s-trans-methyl vinyl
ketone, acrolein, methyl a-methylvinyl ketone, and a-meth-
ylacrolein are more stable in energy by 0.7, 9.0, 4.0, and
R2
R1
methyl a-methylvinyl ketone,
the methyl group attached to
ˆ
H2C
δ +
O
δ −
C O increases
a
negative
Figure 8.
charge on the O atom, while
Chem. Eur. J. 2003, 9, 2419 2438
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2429

Y. Tamaru et al.
FULL PAPER
13.7 kJmolÀ1, respectively. The unusual stabilization of s-cis
N
N
N
ˆ
conformers is probably attributed to (C )O ¥¥¥ H-Cb type
O
O
O
electrostatic attractive interaction [d Cb ¥¥¥ O; 2.108 ä (8i),
2.008 ä (8j), 2.148 ä (8k), 2.162 ä (8l)].
O
N
O
N
O
N
Ts
Ts
Ts
O
O
O
A large amount of asynchronicity for [2 ‡ 2] cycloaddition
(Figures 7 and 9a, c), with the carbonyl (or cyano) group
being exposed to the surroundings, is in good accord with a
11a (1 h, 50%)
11c (10 h, 66%)
11b (6 h, 60%)
Figure 11. [3 ‡ 2] Cycloaddition of 2a, 2m, and 2o with 2,4,6-trimethyl-
benzonitrile N-oxide. Reaction conditions: 2 (0.5 mmol) and nitrile oxide
(1 mmol) in dry dioxane (1.5 mL) at 258C under N2.
large solvent effect (see above). A small difference in the Eact
,
[2 ‡ 2] is also in good accord with the fact that this process is
tolerant to a wide range of alkenes and alkynes (see above).
Surprisingly, the inverse electron demand Diels Alder
reaction of 2g and acrolein exhibited no facial stereoselectiv-
ity and furnished 10e as a mixture of 1:1 diastereomers,
if they violated both the Woodward Hoffmann rule and the
Fukui frontier orbital theory, and readily underwent [2 ‡ 2]
cycloaddition with a wide variety of terminal alkynes, alkenes,
and 1,3-dienes irrespective of their electronic nature under
strictly thermal activation reaction conditions (70 1008C)
and provided 3-substituted (Z)-methylenecyclobutenes 6,
3-substituted methylenecyclobutanes 7 and 8, and 3-vinyl-
methylenecyclobutanes 9, respectively, in good to excellent
yields. Internal alkynes, alkenes, and 1,3-dienes were all
unreactive. The [2 ‡ 2] cycloaddition was concluded to
proceed via a concerted [(p2s‡p2s)allene ‡ p2s] H¸ckel transition
state on the basis of stereochemical relationships between the
starting alkynes/alkenes/1,3-dienes and the products as well as
quantum mechanical methods. With some highly polarized
alkenes (enones) and nitrile oxide, on the other hand, 2
although the event tookplace at the C carbon next to a
4
stereogenic center C5 [Eq. (16)]. The non-stereoselective
formation of 10 was also confirmed spectroscopically
1
(400 MHz H NMR) for the other enones listed in Table 7.
CHO
•
4
80 °C
5
O
+
+
(16)
O
N
O
N
Ts
Ts
16 h
O
O
N
Ts
O
O
2g
20 equiv
10e (46)
[ca. 1:1]
8m (35)
[ca. 1:1]
O
This inconsistency was, however, resolved by inspections of
the X-ray structure of 2g (Figure 10); the TS structures are
shown in Figure 9b and d. The C5-methyl group of 2g lies close
to the oxazolidinone plane. Furthermore, enones approach
ˆ
reacted selectively at the internal C4 Ca bond and underwent
[4 ‡ 2] and [3 ‡ 2] cycloadditions to give spiro compounds 10
and 11, respectively. The competition between [2 ‡ 2] and
[4 ‡ 2] cycloadditions observed for some enones was ration-
alized on the basis of the relative activation energies of these
two processes obtained by quantum mechanical calculations.
The allene bonds of 2 significantly deviate from linearity
(173 1768) owing to an attractive nO( SO) À p*(Ca Cb)
charge transfer type interaction. The unique structure and
reactivity associated with 2 may be primarily attributed to a
ˆ
the C4 Ca p-bond with their two terminal p-orbitals not co-
axially, but inclined a little away from C5 (an endo-approach
with respect to the enamide moiety of 2g). Accordingly, in
such a transition state, enones would react with 2g without
perceiving the C5-Me group.
ˆ
ˆ
ˆ
low-lying LUMO (Ca Cb) that is substantiated by a through-
ˆ
space s*(N SO2) À p*(Ca Cb) orbital interaction.
Experimental Section
Figure 10. Chem 3D view of 2g and top and bottom face approaches of
enones. Double-headed arrows represent an approaching direction of
enones (for clarity, p-tolyl is replaced by Me).
Reactions employed oven-dried glassware unless otherwise noted. Thin-
layer chromatography (TLC) employed glass 0.25 mm silica gel plates with
UV indicator (Merck, silica gel 60F254). Flash chromatography columns
were packed with 230 400 mesh silica gel as a slurry in hexane. Gradient
flash chromatography was conducted eluting with a continuous gradient
from hexane to the indicated solvent. Melting points were determined on a
Yanaco apparatus and are uncorrected. Boiling points refer to the
Kugelrohr oven temperatures. Proton and carbon NMR data were obtained
with a JEOL-GX400 with tetramethylsilane as an internal standard.
Coupling patterns: q ˆ quartet, quint ˆ quintet. Chemical shift values were
given in ppm downfield from the internal standard. Infrared spectra were
recorded with a JASCO A-100 FT-IR spectrophotometer. High resolution
The results listed in Table 7 and Equation (16) suggest that
ˆ
the C4 Ca double bonds of 2 possess an enamine-like
reactivity. Accordingly, [3 ‡ 2] cycloaddition of 2 with nitrile
oxide was examined. Indeed, as was expected, 2a,m,o all
reacted smoothly with 2,4,6-trimethylbenzonitrile N-oxide[36]
ˆ
at the internal C4 Ca bonds at room temperature and
selectively provided diazadioxaspiro compounds 11a c in
mass spectra (HRMS) were measured with
a JEOL JMS-DX303.
moderate yields (Figure 11).
Combustion analyses were performed by the Instrumental Analysis Center
of Nagasaki University. Analysis agreed with the calculated values within
‡0.4%.
Solvents and reagents: THF (tetrahydrofuran), Et2O, and dioxane were
distilled from sodium/benzophenone under N2 prior to use. Triethylamine
was distilled from CaH2 under N2. Alkenes, alkynes, enones were distilled
prior to use in the presence of a small amount of p-methoxyphenol. 3,4-
Dihydro-2H-pyran (Tokyo Chemical Industry) and but-2-yn-1,4-diol (Na-
Conclusion
In this article, we have disclosed for the first time that the
terminal allene Ca Cb bonds of 2 showed a reaction profile as
ˆ
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Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
calai Tesque) were purchased and used without further purification. o- and
p-Toluenesulfonyl isocyanates, phenyl isocyanate (Aldrich), chlorosulfonyl
isocyanate, and 2,2,2-trichloroethanol (Tokyo Chemical Industry) were
purchased and distilled prior to use. Methanesulfonyl isocyanate[37] and
benzoyl isocyanate[38] were prepared according to the literature procedure.
a-Methylacryloyl isocyanate was a gift from Nippon Paint Co. Chloroprene
and 1-chloro-1,3-butadiene were gifts from Tosoh Corp. (E)-b-Monodeu-
terio-ethylstyrene (90% atom D),[39] (Z)-b-monodeuteriostyrene (96%
atom D),[40] dienes (1-triisopropylsiloxy-1,3-diene,[41] 2-triisopropylsiloxy-
1,3-diene,[41] 1-phenyl-3-triisopropylsiloxy-1,3-diene,[41] 2-methyl-3-triiso-
2) This solid was heated under reflux in toluene (20 mL) under N2 for 6 h.
2,2,2-Trichloroethoxysulfonyl isocyanate was isolated as a colorless liquid
(2.30 g, 34%), after removal of toluene and purification by means of
Kugelrohr distillation under reduced pressure (100 1208C/1.0 mm Hg).[49]
The isocyanate was rather unstable and was used immediately after
distillation.
3) 2,2,2-Trichloroethoxysulfonyl isocyanate (2.3 g, 9 mmol) was added at
08C under N2 to
a solution of 1,1-dimethylbut-2-yn-1,4-diol (0.47 g,
4.1 mmol) and triethyl amine (1.3 mL, 8.8 mmol) in THF (5 mL). The
mixture was allowed to warm to room temperature and stirred for 0.5 h.
Addition of 2n HCl, extraction with ethyl acetate, washing the organic
phase with water, followed by drying (MgSO4) and concentration, gave an
yellow oil (3.5 g, 140%). This crude material was subjected to the
cyclization to give 2r [Eq. (4)].
propylsiloxy-1,3-diene,[42] 2-trimethylsilylmethyl-1,3-diene,[43] 5-trimethyl-
silyl-1,3-pentadiene),[43] [Pd2(dba)3] ¥ CHCl3
and [Pd(PPh3)4][45] were
[44]
prepared according to the literature procedure. All other organic and
inorganic materials were used as received from commercial sources or
purified by standard procedures.
Preparation of [D2]-a-trimethylsiloxystyrene: A solution of acetophenone
(60 mmol), NaOH (5 mmol) and D2O [99% D] (2 mol) was stirred at room
temperature for 16 h under N2. The reaction mixture was diluted with dry
Et2O (20 mL) and separated. The organic layer was dried (MgSO4),
filtered, concentrated, and distilled by Kugelrohr (1208C/50 mm Hg).
[D3]Acetophenone [96% atom D] was obtained in 93% yield. To a solution
of LDA (48 mmol) in dry THF (30 mL) prepared at À788C, [D3]aceto-
phenone (48 mmol) was added dropwise over 30 min and stirred for an
additional 30 min. TMSCl (79 mmol) was added slowly over 10 min at
À788C, and the reaction mixture was allowed to warm to room temper-
ature and stirring was continued for 30 min. After addition of dry hexane
(20 mL) and filtration of white solid (LiCl), the solvents were distilled
under ambient pressure and the residue was distilled by Kugelrohr (1358C/
30 mm Hg) to give [D2]-a-trimethylsiloxystyrene (96% atom D) in 62%
yield.
General procedure for the preparation of substituted but-2-yn-1,4-diols:
1) 3,4-Dihydro-2H-pyran (4.6 mL, 50 mmol) was added in one portion at
08C to a mixture of propargyl alcohol (50 mmol) and a catalytic amount of
p-toluenesulfonic acid (0.2 g, 1 mmol) in dry THF (30 mL). The mixture
was allowed to warm to room temperature and stirred for 2 h. After
neutralization with sat. NaHCO3 and concentration, the reaction mixture
was extracted with ethyl acetate (2 Â 20 mL). The combined organic
extracts were dried (MgSO4), filtered, concentrated, and distilled by means
of Kugelrohr to give 3-(tetrahydro-2-pyranoxy)-1-propyne (1288C/55 mm
Hg, 84%).
2) A 200 mL three-necked round bottomed flask, equipped with a septum,
a reflux condenser at the top bearing N2 balloon, and a dropping funnel,
was purged with nitrogen. Dry THF (50 mL) and 3-(tetrahydro-2-
pyranoxy)-1-propyne (7.0 g, 50 mmol) were introduced through a septum
via syringe. The mixture was cooled in a dry ice/isopropanol bath (À788C).
A solution of nBuLi (1.6m in hexane, 32 mL, 50 mmol) was added slowly
via the dropping funnel and the reaction mixture was stirred for 2 h at the
same temperature. An appropriate aldehyde (50 mmol) or ketone
(50 mmol) was added at À788C and the mixture was stirred for 1 h at
the same temperature. After allowing to warm to ambient temperature, sat.
NH4Cl (20 mL) was added and the mixture was extracted with ethyl
acetate. The extract was washed with brine, dried (MgSO4), filtered, and
concentrated in vacuo. The residue was distilled under reduced pressure by
means of Kugelrohr to afford 1-substituted 4-(tetrahydro-2-pyranoxy)but-
2-yn-1-ol in quantitative yield.
Preparation of [D5]-a-methacrylonitrile: 30% H2SO4 (36 mL) was added
dropwise at 08C over 1 h to a solution of [D6]acetone (99.5% atom D,
Aldrich) (136 mmol) and KCN (108 mmol) in water (30 mL). After stirring
for 0.5 h at 08C, the reaction mixture was extracted with Et2O (2 Â 20 mL),
washed with sat. NaHCO3, and dried (MgSO4). Et2O was removed under
reduced pressure and the residue was distilled by Kugelrohr (90 1008C/
10 15 mm Hg) to afford a [D6]acetone cyanohydrin in 64% yield. To a
mixture of
a [D6]acetone cyanohydrin (69 mmol) and dry pyridine
(76 mmol) was added thionyl chloride (138 mmol) at 08C over 15 min,
and the mixture was allowed to warm to ambient temperature and stirred
for an additional 3 h. The mixture was poured into water (10 mL) at 08C
and extracted with Et2O (2 Â 20 mL). The combined extracts were washed
with sat. NaHCO3 and brine and dried (MgSO4). After distillation of the
solvents under ambient pressure, and the crude resulting product was
distilled by Kugelrohr (1008C/150 mm Hg) to provide [D5]-a-methacrylo-
nitrile (97% atom D) in 20% yield.
3) In a 100 mL round bottomed flask, a mixture of 1-substituted 4-(tetra-
hydro-2-pyranoxy)but-2-yn-1-ol (30 mmol), methanol (30 mL), and p-
toluenesulfonic acid (0.57 g, 3.0 mmol) was stirred for 2 h at ambient
temperature. After addition of sat. NaHCO3, the mixture was concentrated
and the residue was partitioned into ethyl acetate and brine. The organic
phase was dried (MgSO4), filtered, and concentrated in vacuo. The residue
was distilled under reduced pressure by means of Kugelrohr to afford
1-substituted but-2-yn-1,4-diols in reasonable yield (80 95%).
Preparation of 2-phenyl-1,3-butadiene: 1) Acetophenone (5 mL, 40 mmol)
dissolved in THF (15 mL) was added dropwise over 0.5 h at 08C to a
solution of vinylmagnesium bromide (50 mL, 50 mmol, 1m THF solution,
Aldrich). The mixture was allowed to warm to room temperature and
stirred for 0.5 h at the same temperature. The mixture was filtered through
a glass filter. The filtrate was partitioned into 2n HCl and Et2O. The
organic layer was washed with brine, dried (MgSO4), and concentrated in
vacuo. The oily residue was purified by distillation (908C/1 mm Hg) to give
2-phenyl-3-buten-1-ol in 88% yield.
General procedure for the preparation of but-2-yn-1,4-diol biscarbamates
1a q: Dry THF (50 mL), the but-2-yn-1,4-diol derivative (30 mmol), and
triethylamine (10 mL, 66 mmol) were introduced via syringe to a 200 mL
two-necked round bottomed flask, equipped with a septum and a nitrogen
balloon. The mixture was cooled to 08C and then an appropriate isocyanate
(66 mmol) was introduced dropwise. After completion of addition, the
mixture was allowed to warm to ambient temperature and stirred for 2 h,
during which a lot of white precipitate appeared. The mixture was diluted
with THF (50 mL) washed with 2n HCl and then brine. The THF layer was
dried (MgSO4), filtered, and concentrated in vacuo to give a white solid.
The solid was crystallized from THF/AcOEt. Compound 1e tends to
polymerize during recrystallization; hence, 1e was subjected to the
transformation to 2e without purification (runs 10 and 11, Table 1).
2) 2-Phenyl-3-buten-1-ol (2.4 g, 16 mmol), NaHSO4 (0.01 g, 5 mol%), and
hydroquinone (18 mg, 1 mol%) were heated at 1208C under reduced
pressure (30 mm Hg) in a Kugelrohr oven. Once dehydration started, the
pressure was reduced (10 mm Hg) in order to remove the product as
quickly as possible (0.9 g, 43%).
Preparation of (E)-1-phenyl-1,3-butadiene: 1) A solution of allyl bromide
(19.4 mL, 225 mmol) in Et2O (150 mL) was added dropwise over 1 h at 08C
to
a stirred mixture of benzaldehyde (15.3 mL, 150 mmol) and Mg
(10.9 mg, 450 mmol) in Et2O (20 mL). The mixture was allowed to warm
to room temperature and stirred for 1 h. The mixture was filtered through a
glass filter and the filtrate was washed with 2n HCl. The organic layer was
washed with brine, dried (MgSO4), and concentrated. Distillation (1008C/
1 mm Hg) of the residue furnished 1-phenyl-3-buten-1-ol in 96% yield.
1,1-Dimethylbut-2-yn-1,4-diol bis(N-2,2,2-trichloroethoxysulfonyl) carba-
mates (1r): 1) A solution of 2,2,2-trichloroethanol (2.8 mL, 30 mmol) in
Et2O (30 mL) was added over 0.5 h at 08C under N2 to a solution of
chlorosulfonyl isocyanate (2.8 mL, 32 mmol) in dry Et2O (10 mL). The
mixture was allowed to warm to room temperature and stirred for 2 h. The
solvent was removed, and the residue was recrystallized from Et2O to give
N-chlorosulfonyl 2,2,2-trichloroethyl carbamate as a white solid (7.99 g,
92%).
2) 1-Phenyl-3-buten-1-ol (6.22 g, 42 mmol), NaHSO4 (0.29 g, 5 mol%), and
hydroquinone (46 mg, 1 mol%) were heated at 1208C under reduced
pressure (30 mm Hg) in a Kugelrohr oven. Once dehydration started, the
Chem. Eur. J. 2003, 9, 2419 2438
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2431

Y. Tamaru et al.
FULL PAPER
pressure was reduced (10 mm Hg) in order to remove the product as
quickly as possible (2.35 g, 43%).
3H), 4.95 (dq, J ˆ 7.4, 4.4 Hz, 1H), 5.71 (d, J ˆ 4.4 Hz, 2H), 7.36 (d, J ˆ
8.3 Hz, 2H), 7.92 (d, J ˆ 8.3 Hz, 2H); elemental analysis calcd (%) for
C14H15NO4S: C 57.32, H 5.15, N 4.77, S 10.93; found: C 57.72, H 5.15, N 4.70,
S 10.55.
4-(2-Butenylidene)-3-(p-toluenesulfonyl)oxazolidin-2-one (5h): 1H NMR
(400 MHz, CDCl3): d ˆ 1.07 (t, J ˆ 7.3 Hz, 3H), 2.20(ddq, J ˆ 6.1, 7.3,
13.4 Hz, 2H), 2.46 (s, 3H), 4.78 (dd, J ˆ 4.1, 11.7 Hz, 1H), 4.82 (dq, J ˆ 4.1,
11.7 Hz, 1H), 6.15 (tt, J ˆ 4.1, 6.1 Hz, 1H), 7.36 (d, J ˆ 8.3 Hz, 2H), 7.92 (d,
J ˆ 8.3 Hz, 2H).
General procedure for the preparation of 3-tosyl-4-vinylidene-2-oxazoli-
dinones 2 and 5: Compound 1 (0.5 mmol) and [Pd2(dba)3] ¥ CHCl3 (2.5 mg,
2.5 mmol) were placed in a 25 mL two-necked round bottomed flask, one of
the two necks being sealed with a septum and the other fitted with a reflux
condenser at the top bearing a nitrogen balloon. The flaskwas purged with
N2, and THF (5 mL) and triethyl amine (7 mL, 50 mmol) were added
through a septum. The mixture was stirred at the temperature and for the
period of time indicated in Tables 1 and 2 and Equations (3) and (4). The
reaction was monitored by TLC in hexane/EtOAc 2:1: Rf (1) ˆ0.05, Rf
(2a) ˆ Rf (2b) ˆ Rf (2c) ˆ Rf (2d) ˆ Rf (2e) ˆ0.35; in hexane/EtOAc 1:1, Rf
(1) ˆ 0.1, Rf (2g) ˆ Rf (5g) ˆ0.6; Rf (2h) ˆ Rf (5h) ˆ 0.63; Rf (2i) ˆ Rf
(5i) ˆ 0.63; Rf (2j) ˆ Rf (5j) ˆ 0.74; Rf (2k) ˆ Rf (5k) ˆ0.74; Rf (2l) ˆ Rf
(5l) ˆ 0.74; Rf (2m) ˆ Rf (5m) ˆ 0.74; Rf (2n) ˆ Rf (5n) ˆ0.74; Rf (2o) ˆ Rf
(5o) ˆ 0.74; Rf (2p) ˆ 0.77). The mixture was diluted with ethyl acetate and
filtered through a Celite pad. The filtrate was concentrated in vacuo and
the residue was purified by means of silica gel column chromatography
over silica gel or in some cases, by crystallization. The yields refer to the
averaged values of experiments undertaken at least two times.
5-Isopropyl-3-(p-toluenesulfonyl)-4-vinylideneoxazolidin-2-one (2i): Ob-
tained as a mixture with 5i in a ratio of 2.5:1: IR (neat): n ˆ 1790 (s), 1380
(m), 1170 (m); 1090 (m), 1050 (m), 1010 (m), 890 (m), 800 cmÀ1 (m);
1H NMR (400 MHz, CDCl3): d ˆ 0.81 (d, J ˆ 6.7 Hz, 3H), 0.97 (d, J ˆ
6.7 Hz, 3H), 1.92 (dhept, J ˆ 3.7, 6.7 Hz, 1H), 2.46 (s, 3H), 4.84 (q, J ˆ
3.7 Hz, 1H), 5.70 (d, J ˆ 3.7 Hz, 1H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ
8.4 Hz, 2H); HRMS: m/z (%): calcd for C15H17NO4S: 307.0878; found:
‡
307.0873 (26) [M] , 198 (6), 152 (76), 139 (37), 91 (100).
4-(2-Isopentenylidene)-3-p-toluenesulfonyloxazolidin-2-one (5i): 1H NMR
(400 MHz, CDCl3): d ˆ 1.09 (d, J ˆ 6.8 Hz, 3H), 1.11 (d, J ˆ 6.8 Hz, 3H),
2.45 (s, 3H), 2.48 (dhept, J ˆ 4.4, 6.8 Hz, 1H), 4.80 (dd, J ˆ 4.4, 5.5 Hz, 1H),
4.83 (dd, J ˆ 4.4, 5.5 Hz, 1H), 6.08 (dt, J ˆ 4.4, 5.5 Hz, 1H), 7.36 (d, J ˆ
8.4 Hz, 2H), 7.91 (d, J ˆ 8.4 Hz, 2H).[17]
3-(p-Toluenesulfonyl)-4-vinylideneoxazolidin-2-one (2a): CCDC-181558;
m.p. 101.2 103.08C (AcOEt/hexane); IR (KBr): n ˆ 1805 (s), 1385(s), 1370
(s), 1290 (s), 1230 (s), 1180 (s), 1160 (s), 1150 (s), 650 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 2.46 (s, 3H), 4.86 (t, J ˆ 4.8 Hz, 2H), 5.71 (t, J ˆ
4.8 Hz, 2H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.93 (d, J ˆ 8.4 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d ˆ 21.8, 63.9, 92.6, 103.8, 128.3, 129.9, 134.1, 146.1,
150.3, 192.0; elemental analysis calcd (%) for C12H11NO4S: C 54.88, H 4.18,
N 5.28, S 12.09; found: C 54.57, H 4.15, N 5.13, S 12.00.
5-Cyclohexyl-3-(p-toluenesulfonyl)-4-vinylideneoxazolidin-2-one
(2j):
Obtained as a mixture with 5j in a ratio of 2.5:1: IR (neat): n ˆ 1790 (s),
1380 (s), 1290 (m), 1220 (m), 1170 (s); 1090 (m), 990 (m), 810 cmÀ1 (m);
1H NMR (400 MHz, CDCl3): d ˆ 1.09 1.30 (m, 11H), 2.38 (s, 3H), 4.78 (m,
1H), 5.70 (d, J ˆ 4.0 Hz, 2H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz,
2H); HRMS: m/z (%): calcd for C18H21NO4S: 347.1191; found: 347.1209
3-(o-Toluenesulfonyl)-4-vinylideneoxazolidin-2-one (2b): CCDC-181724;
m.p. 84.0 84.58C (AcOEt/hexane); IR (KBr): n ˆ 1805 (s), 1385 (s), 1370
(s), 1290 (s), 1230 (s), 1180 (s), 1160 (s), 1150 (s), 650 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3):d ˆ 2.68 (s, 3H), 4.80 (t, J ˆ 4.8 Hz, 2H), 5.65 (t, J ˆ
4.8 Hz, 2H), 7.27 7.58 (m, 3H), 8.03 (d, J ˆ 8.4 Hz, 1H); elemental analysis
calcd (%) for C12H11NO4S: C 54.88, H 4.18, N 5.28, S 12.09; found: C 54.47,
H 4.14, N 5.15, S 12.41.
‡
(17) [M] , 192 (100).[17]
4-(2-Cyclopentylvinylidene)-3-p-toluenesulfonyloxazolidin-2-one
(5j):
1H NMR (400 MHz, CDCl3): d ˆ 1.09 1.30 (m, 11H), 2.38 (s, 3H), 4.78
(m, 1H), 5.70 (d, J ˆ 4.0 Hz, 2H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ
8.4 Hz, 2H).
5-Phenyl-3-p-toluenesulfonyl-4-vinylidene-2-oxazolidinone (2k): CCDC-
181726, the sample was prepared by repeated recrystallization; m.p. 107.9
108.88C (CH2Cl2/hexane, contaminated by a trace amount of 5k); IR
(KBr): n ˆ 1790 (s), 1380 (s), 1330 (s), 1295 (s), 1230 (s), 1200 (s), 1190 (s),
3-Methanesulfonyl-4-vinylideneoxazolidin-2-one (2c): oil; IR (neat): n ˆ
1778 (s), 1664 (s), 1371 (s), 1151 (s), 999 (s), 771 cmÀ1 (s); 1H NMR
(300 MHz, C6D6): d ˆ 2.46 (s, 3H), 3.70 (t, J ˆ 4.5 Hz, 2H), 5.06 (t, J ˆ
4.5 Hz, 2H); 13C NMR (100 MHz, CDCl3): d ˆ 40.4, 63.8, 92.4, 102.9, 154.4,
1
1150 (s), 650 cmÀ1 (s); H NMR (400 MHz, CDCl3): d ˆ 2.46 (s, 3H), 5.56
‡
191; MS m/z (%): 189 (1) [M] , 163 (30), 116 (16), 97 (26), 83 (100), 79 (36);
(dd, J ˆ 4.0, 10.6 Hz, 1H), 5.67 (dd, J ˆ 4.0, 10.6 Hz, 1H), 5.88 (t, J ˆ 4.0 Hz,
1H), 7.19 (d, J ˆ 8.1 Hz, 2H), 7.93 (d, J ˆ 8.1 Hz, 2H); elemental analysis
calcd (%) for C18H15NO4S: C 63.33, H 4.43, N 4.10, S 9.39; found: C 63.26,
H 4.45, N 4.16, S 9.40.
HRMS: m/z (%): calcd for C6H7NO4S: 189.0096; found: 189.0117 (72)
‡
[M] , 174 (44), 162 (100).[17]
3-Benzoyl-4-vinylideneoxazolidin-2-one (2d): m.p. 103.6 104.58C
(CH2Cl2/hexane); IR (KBr): n ˆ 1790 (s), 1690 (s), 1360 (s), 1300 (s),
1160 (s), 1060 cmÀ1 (s); 1H NMR (60 MHz, CDCl3): d ˆ 5.01 (t, J ˆ 4.5 Hz,
2H), 5.60 (t, J ˆ 4.5 Hz, 2H), 7.27 7.95 (m, 5H); elemental analysis calcd
(%) for C12H9NO3: C 66.97, H 4.22, N 6.51; found: C 67.03, H 4.37, N 6.43.
4-(2-Phenylvinylidene)oxazolidin-2-one (5k): 1H NMR 400 MHz, CDCl3:
d ˆ 2.42 (s, 3H), 4.80 (d, J ˆ 3.9 Hz, 2H), 6.98 (t, J ˆ 3.9 Hz, 1H), 7.24 (d,
J ˆ 8.1 Hz, 2H), 7.89 (d, J ˆ 8.1 Hz, 2H).
5-tert-Butyl-4-vinylidene-3-p-toluenesulfonyloxazolidin-2-one (2l): m.p.
69.1 71.28C (CH2Cl2/hexane, contaminated with a trace amount of 5l);
IR (KBr): n ˆ 1800 (s), 1380 (s), 1220 (s), 1190 (s), 1180 (s), 1150 (s), 1060
(w), 670 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.13 (s, 9H), 2.46 (s,
3H), 4.60 (t, J ˆ 3.7 Hz, 1H), 5.68 (dd, J ˆ 1.5, 3.7 Hz, 1H), 5.71 (dd, J ˆ 1.5,
3.7 Hz, 1H), 7.36 (d, J ˆ 8.3 Hz, 2H), 7.92 (d, J ˆ 8.3 Hz, 2H); elemental
analysis calcd (%) for C16H19NO4S: C 59.79, H 5.96, N 4.36, S 9.98; found: C
59.53, H 5.90, N 4.28, S 9.66.
3-(a-Methylacryloyl)-4-vinylideneoxazolidin-2-one (2e): m.p. 126.3
126.78C (Et2O/hexane); IR (KBr): n ˆ 1780 (s), 1690 (s), 1380 (s), 1310
(s), 1270 (s), 1170 (s), 1075 (s), 750 cmÀ1 (m); 1H NMR (400 MHz,
[D6]DMSO): d ˆ 1.92 (s, 3H), 5.04 (t, J ˆ 4.8 Hz, 2H), 5.47 (brs, 2H), 5.59
(t, J ˆ 4.8 Hz, 2H); elemental analysis calcd (%) for C9H9NO3: C 60.33, H
5.06, N 7.82; found: C 60.08, H 4.98, N 7.65.
5-Methyl-3-(p-toluenesulfonyl)-4-vinylideneoxazolidin-2-one
(2g):
CCDC-188289; m.p. 68.2 70.28C (Et2O/hexane, contaminated by a trace
amount of 5g); IR (KBr): n ˆ 1780 (s), 1370 (s), 1170 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 1.43 (d, J ˆ 6.6 Hz, 3H), 2.46 (s, 3H), 5.09 (tq, J ˆ
4.5, 6.2 Hz, 1H), 5.71 (dd, J ˆ 4.5, 10.6 Hz, 1H), 5.74 (dd, J ˆ 4.5, 10.6 Hz,
1H), 7.36 (d, J ˆ 8.1 Hz, 2H), 7.90 (d, J ˆ 8.1 Hz, 2H); elemental analysis
calcd (%) for C13H13NO4S: C 55.90, H 4.69, N 5.01, S 11.48; found: C 55.90,
H 4.69, N 5.05, S 11.40.
4-(2-Propenylidene)-3-(p-toluenesulfonyl)oxazolidin-2-one (5g): 1H NMR
(400 MHz, CDCl3): d ˆ 1.90 (d, J ˆ 7.2 Hz, 3H), 2.46 (s, 3H), 4.76 (dd, J ˆ
4.0, 11.7 Hz, 1H), 4.80 (dd, J ˆ 4.5, 11.7 Hz, 1H), 6.07 (tq, J ˆ 4.0, 7.2 Hz,
1H), 7.36 (d, J ˆ 8.1 Hz, 2H), 7.90 (d, J ˆ 8.1 Hz, 2H).
5-Ethyl-4-vinylidene-3-(p-toluenesulfonyl)oxazolidin-2-one (2h): Ob-
tained as a mixture with 5h in a ratio of 1.7:1: IR (neat): n ˆ 1790 (s),
1370 (s), 1340 (m), 1280 (m), 1250 (m), 1190 (s), 1150 (m), 1090 (m),
800 cmÀ1 (m); 1H NMR (400 MHz, CDCl3): d ˆ 0.90 (t, J ˆ 7.4 Hz, 3H), 1.67
(dquint, J ˆ 7.4, 14.6 Hz, 1H), 1.79 (ddq, J ˆ 4.4, 14.6, 7.4 Hz, 1H), 2.46 (s,
4-(2-tert-Butylvinylidene)-3-p-toluenesulfonyloxazolidin-2-one
(5l):
1H NMR (400 MHz, CDCl3): d ˆ 0.91 (s, 9H), 2.46 (s, 3H), 4.77 (dd, J ˆ
4.4, 11.4 Hz, 1H), 4.83 (dd, J ˆ 4.4, 11.4 Hz, 1H), 6.01 (t, J ˆ 4.4 Hz, 1H),
7.36 (d, J ˆ 8.3 Hz, 2H), 7.92 (d, J ˆ 8.3 Hz, 2H).
5,5-Dimethyl-3-p-toluenesulfonyl-4-vinylideneoxazolidin-2-one
(2m):
CCDC-181555, the sample was prepared by repeated recrystallization;
m.p. 93.4 94.68C (CH2Cl2/hexane, contaminated with a trace of 5m); IR
(KBr): n ˆ 1785 (s), 1380 (s), 1170 (s), 906 (s), 728 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 1.43 (s, 6H), 2.43 (s, 3H), 5.76 (brs, 2H), 7.38 (d, J ˆ
8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz, 2H); elemental analysis calcd (%) for
C14H15NO4S: C 57.32, H 5.15, N 4.77, S 10.93; found: C 57.19, H 5.13, N 4.79,
S 10.79.
4-(2-Isobutenylidene)-3-p-toluenesulfonyloxazolidin-2-one (5m): 1H NMR
(400 MHz, CDCl3): d ˆ 1.90 (s, 6H), 2.43 (s, 3H), 4.76 (brs, 2H), 7.38 (d, J ˆ
8.4 Hz, 2H), 7.88 (d, J ˆ 8.4 Hz, 2H).
2432
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
3-p-Toluenesulfonyl-4-vinylidene-1-oxa-3-azaspiro[4.4]nonan-2-one (2n):
CCDC 181553, the sample was prepared by repeated recrystallization;
m.p. 105.5 106.58C (CH2Cl2/hexane, contaminated with a trace amount of
5n); IR (KBr): n ˆ 1780 (s), 1370 (s), 1230 (s), 1160 (s), 1130 (m), 960 (s),
General procedure for the thermal cycloaddition of 2 with alkynes, alkenes,
enones, and nitrile oxides: An appropriate combination of 2 and an alkyne,
an alkene, an enone, or a nitrile oxide was heated in a thermostated oil bath
under N2. For the detail of the experimental conditions (T, solvent, t, etc.),
see Tables 5 7, Figure 11 and relevant Equations.
1
750 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 1.66 1.88 (m, 6H), 1.98
2.12 (m, 2H), 2.46 (s, 3H), 5.72 (s, 2H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.93 (d, J ˆ
8.4 Hz, 2H); elemental analysis calcd (%) for C17H17NO4S: C 60.17, H 5.37,
N 4.39, S 10.04; found: C 59.94, H 5.28, N 4.26, S 10.03.
(Z)-4-(3-Phenyl-2-cyclobutenylidene)-3-p-toluenesulfonyloxazolidin-2-
one [(Z)-6a]: m.p. 153.9 154.18C (CH2Cl2/hexane); IR (KBr): n ˆ 1800
(s), 1380 (s), 1260 (s), 1108 (m), 750 (s), 650 cmÀ1 (s); 1H NMR (400 MHz,
CDCl3): d ˆ 2.45 (s, 3H), 3.15 (s, 2H), 4.87 (s, 2H), 6.98 (s, 1H), 7.32 7.41
(m, 5H), 7.46 (d, J ˆ 8.3 Hz, 2H), 7.96 (d, J ˆ 8.3 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d ˆ 21.7, 33.7, 66.5, 112.6, 116.9, 125.6, 126.9, 128.3,
128.7, 129.0, 129.9, 133.2, 134.7, 145.9, 147.6, 152.4; elemental analysis calcd
(%) for C20H17NO4S: C 64.74, H 4.73, N 4.01, S 8.64; found: C 64.76, H 4.72,
N 3.77, S 8.57.
4-Cyclopenthylidenemethylene-3-p-toluenesulfonyloxazolidin-2-one (5n):
1H NMR (400 MHz, CDCl3): d ˆ 1.66 1.88 (m, 6H), 1.98 2.12 (m, 2H),
2.46 (s, 3H), 4.75 (brs, 2H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.83 (d, J ˆ 8.4 Hz,
2H).
3-p-Toluenesulfonyl-4-vinylidene-1-oxa-3-azaspiro[4.5]decan-2-one (2o):
m.p. 93.0 94.28C (Et2O/hexane, contaminated with a trace amount of
5o); IR (KBr): n ˆ 1790 (s), 1380 (s), 1180 (s), 910 (m), 810 cmÀ1 (m);
1H NMR (400 MHz, CDCl3): d ˆ 1.46 1.85 (m, 10H), 2.46 (s, 3H), 5.71 (s,
2H), 7.38 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz, 2H); elemental analysis
calcd (%) for C17H19NO4S: C 61.24, H 5.74, N 4.20, S 9.62; found: C 61.38, H
5.69, N 4.25, S 9.72.
(Z)-4-(3-Methoxycarbonyl-2-cyclobutenylidene)-3-p-toluenesulfonyloxa-
zolidin-2-one [(Z)-6b]: m.p. 66.0 66.58C (CH2Cl2/hexane); IR (KBr): n ˆ
1800 (s), 1680 (s), 1260 (s), 1120 (s), 1080 (s), 730 cmÀ1 (m); 1H NMR
(400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 3.06 (s, 2H), 3.81 (s, 3H), 4.87 (s, 2H),
7.37 (d, J ˆ 8.8 Hz, 2H), 7.91 (s, 1H), 7.93 (d, J ˆ 8.8 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d ˆ 21.8, 33.9, 51.8, 66.2, 113.9, 119.2, 128.4, 130.0, 134.2,
137.9, 142.5, 146.4, 151.9, 163.0; HRMS: m/z (%): calcd for C16H15NO6S À
4-Cyclohexylidenemethylene-3-p-toluenesulfonyloxazolidin-2-one (5o):
1H NMR (400 MHz, CDCl3):d ˆ 1.46 1.85 (m, 10H), 2.46 (s, 3H), 4.75
(s, 2H), 7.38 (d, J ˆ 8.5 Hz, 2H), 7.90 (d, J ˆ 8.5 Hz, 2H).
CO2: 305.0722; found: 305.0744 (55) [M À CO2] , 91 (100).[17]
(Z)-4-(3-Phenyl-2-cyclobutenylidene)-3-benzoyloxazolidin-2-one
‡
[(Z)-
6c]: m.p. 135.5 136.58C (CH2Cl2/hexane); IR (KBr): n ˆ 1790 (s), 1720
(s), 1690 (s), 1370 (s), 1170 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 3.22
(s, 2H), 5.11 (s, 2H), 6.59 (s, 1H), 7.29 7.79 (m, 10H); HRMS: m/z (%):
calcd for C20H15NO3: 317.1052; found: 317.1068 (31) [M] , 273 (2), 105
(100).[17]
Compound 2p: CCDC-181554; m.p. 110.5 110.98C (CH2Cl2/hexane); IR
(KBr): n ˆ 1800 (s), 1610 (m), 1390 (s), 1280 (s), 1250 (s), 1190 (s), 1180 (s),
1
1110 (m), 1080 (m), 980 (m), 920 cmÀ1 (m); H NMR (400 MHz, CDCl3):
‡
d ˆ 1.51 1.63 (m, 3H), 1.64 1.73 (m, 3H), 1.76 1.87 (m, 2H), 1.99 2.05
(m, 2H), 2.11 2.20 (m, 4H), 2.46 (s, 3H), 5.76 (s, 2H), 7.35 (d, J ˆ 8.6 Hz,
2H), 7.92 (d, J ˆ 8.6 Hz, 2H); elemental analysis calcd (%) for C21H23NO4S:
C 65.43, H 6.01, N 3.63, S 8.32; found: C 65.11, H 5.97, N 3.46, S 8.60.
4-(3-Phenylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-one
(7a):
oil; IR (neat): n ˆ 1795 (s), 1380 (s), 1245 (s), 1164 (s), 750 (s), 700 cmÀ1
(s); 1H NMR (400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 2.76 (dm, J ˆ 15.0 Hz,
1H), 2.99 (dm, J ˆ 15.0 Hz, 1H), 3.24 (dm, J ˆ 16.2 Hz, 1H), 3.49 (dm, J ˆ
16.2 Hz, 1H), 3.65 (quint, J ˆ 8.2 Hz, 1H), 4.60 (dm, J ˆ 12.8 Hz, 1H), 4.70
(brd, J ˆ 12.8 Hz, 1H), 7.21 7.34 (m, 5H), 7.34 (d, J ˆ 8.2 Hz, 2H), 7.92 (d,
J ˆ 8.2 Hz, 2H); 13C NMR (100 MHz, CDCl3): d ˆ 21.7, 35.7, 36.4, 39.3, 66.3,
117.8, 119.4, 126.4, 126.5, 128.4, 128.6, 129.8, 135.1, 144.6, 145.7, 152.5;
HRMS: m/z (%): calcd for C20H19NO4S: 369.1034; found: 369.1030 (81)
SO2
N
•
O
O
2p
‡
[M] , 265 (42), 214(96), 131 (30), 104 (77), 91 (100), 77 (13); elemental
5,5-Dimethyl-4-(2-isobutenylidene)-3-p-toluenesulfonyloxazolidin-2-one
(2q): CCDC-181559; m.p. 126.0 127.28C (CH2Cl2/hexane); IR (KBr): n ˆ
1785 (s), 1370 (s), 1280 (s), 1190 (s), 1180 (s), 1160 (s), 670 cmÀ1 (s);
1H NMR (60 MHz, CDCl3): d ˆ 1.40 (s, 6H), 1.90 (s, 6H), 2.42 (s, 3H), 7.40
(d, J ˆ 8.0 Hz, 2H), 7.90 (d, J ˆ 8.0 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d ˆ 21.7, 22.0, 27.1, 81.3, 110.4, 115.0, 128.0, 129.6, 134.7, 145.5, 149.7, 182.9;
elemental analysis calcd (%) for C16H19NO4S: C 59.79, H 5.96, N 4.36, S
9.56; found: C 59.62, H 5.94, N 4.26, S 9.62.
analysis calcd (%) for C20H19NO4S: C 65.02, H 5.18, N 3.79, S 8.68; found: C
65.19, H 5.25, N 3.64, S 8.53.
(Z)-4-(2,2,3-Trideuterio-3-pentadeuteriophenylcyclobutylidene)-3-p-tol-
uenesulfonyloxazolidin-2-one [Z-[D8]-7a]: 1H NMR (400 MHz, CDCl3):
d ˆ 2.44 (s, 3H), 2.74 (brd, J ˆ 15.0 Hz, 1H), 2.98 (brd, J ˆ 15.0 Hz, 1H),
4.59 (dm, J ˆ 12.1 Hz, 1H), 4.69 (dm, J ˆ 12.1 Hz, 1H), 7.34 (d, J ˆ 8.1 Hz,
2H), 7.93 (d, J ˆ 8.1 Hz, 2H).[17]
(Z)-4-(cis-2-Deuterio-3-phenylcyclobutylidene)-3-p-toluenesulfonyloxa-
zolidin-2-one [(Z)-cis-[D1]-7a]: 1H NMR (400 MHz, CDCl3): d ˆ 2.44 (s,
3H), 2.75 (dm, J ˆ 15.0 Hz, 1H), 2.99 (dm, J ˆ 15.0 Hz, 1H), 3.47 (m, 1H),
3.66 (q, J ˆ 8.30 Hz, 1H), 4.59 (dm, J ˆ 11.7 Hz, 1H), 4.69 (dm, J ˆ 11.7 Hz,
1H), 7.21 7.35 (m, 7H), 7.93 (d, J ˆ 8.4 Hz, 2H).[17]
3-Benzoyl-4-(3-phenylcyclobutylidene)oxazolidin-2-one (7b): m.p. 96.5
97.08C (CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s), 1740 (m), 1690 (s), 1370
(s), 1170 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 2.76 2.94 (m, 2H),
2.99 3.10 (m, 2H), 3.65 (quint, J ˆ 8.2 Hz, 1H), 4.82 (dquint, J ˆ 15.0,
2.7 Hz, 1H), 4.90 (dm, J ˆ 15.0 Hz, 1H), 7.16 7.34 (m, 4H), 7.42 7.48 (m,
2H), 7.54 7.61 (m, 2H), 7.75 7.81 (m, 2H); elemental analysis calcd (%)
for C20H17NO3: C 75.22, H 5.37, N 4.39; found: C 74.95, H 5.42, N 4.31.
3-(2,2,2-Trichloroethoxysulfonyl)-5,5-dimethyl-4-vinylideneoxazolidin-2-
one (2r): m.p. 88.0 88.38C (CH2Cl2/hexane); IR (KBr): n ˆ 1810 (s), 1380
(s), 1310 (m), 1260 (s), 1200 (s), 1170 (m), 1080 (m), 1060 (s), 990 (s), 910
(m), 770 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.60 (s, 6H), 4.99 (s,
2H), 5.76 (s, 2H); HRMS: m/z (%): calcd for C9H10NO5SCl3: 348.9345;
‡
found: 348.9366 (21) [M] , 232 (7), 175 (100).[17]
(Z)-N-p-Toluenesulfonyl 2-(2-oxo-3-p-toluenesulfonyloxazolidin-4-ylide-
ne)ethyl carbamate (3): m.p. 52.0 53.08C (CH2Cl2/hexane); IR (KBr):
n ˆ 1800 (s), 1750 (s), 1600 (w), 1450 (s), 1370 (s), 1090 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 2.46 (s, 3H), 4.68 (d, J ˆ 1.4 Hz, 2H),
4.90 (d, J ˆ 6.1 Hz, 2H), 5.13 (tt, J ˆ 1.4, 6.1 Hz, 1H), 7.35 (d, J ˆ 8.2 Hz,
2H), 7.81 (brs, 1H), 7.89 (d, J ˆ 8.2 Hz, 2H), 7.93 (d, J ˆ 8.2 Hz, 2H);
13C NMR (100 MHz, CDCl3): d ˆ 21.3, 21.4, 63.0, 68.8, 107.5, 126.1, 128.0,
128.2, 129.2, 129.3, 129.4, 129.7, 133.8, 134.9, 144.9, 146.1, 149.9, 152.2;
elemental analysis calcd (%) for C20H20N2O8S2: C 49.99, H 4.19, N 5.83, S
13.35; found: C 49.68, H 4.14, N 5.93, S 13.64.
5,5-Dimethyl-4-(3-phenylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-
2-one (7c): CCDC-181551; m.p. 145.0 146.08C (CH2Cl2/hexane); IR
(KBr): n ˆ 1800 (s), 1740 (m), 1370 (s), 1170 cmÀ1 (m); 1H NMR (400 MHz,
CDCl3): d ˆ 1.45 (s, 3H), 1.56 (s, 3H), 2.43 (s, 3H), 2.95 (ddd, J ˆ 3.0, 7.5,
15.0 Hz, 1H), 3.22 (ddd, J ˆ 3.0, 7.5, 16.5 Hz, 1H), 3.29 (ddt, J ˆ 9.2, 15.0,
3.0 Hz, 1H), 3.47 (ddt, J ˆ 8.8, 16.5, 3.0 Hz, 1H), 3.62 (quint, J ˆ 8.3 Hz,
1H), 7.21 7.30 (m, 7H), 7.92 (d, J ˆ 8.4 Hz, 2H); elemental analysis calcd
(%) for C22H23NO4S: C 66.48, H 5.83, N 3.52, S 8.07; found: C 66.29, H 5.88,
N 3.38, S 7.67.
6-Methyl-8-methylene-tetrahydrooxazolo[3.4]-3,5-dione (4): m.p. 144.6
145.58C (CH2Cl2/hexane); IR (KBr): n ˆ 1805 (s), 1711 (s), 1362 (s), 1333
(s), 1267 (s), 1097 (m), 1072 (m), 885 cmÀ1 (m); 1H NMR (400 MHz,
CDCl3): d ˆ 1.33 (d, J ˆ 7.0 Hz, 3H), 2.51 (dd, J ˆ 9.5, 14.3 Hz, 1H), 2.72
(dd, J ˆ 4.8, 14.3 Hz, 1H), 2.79 (ddq, J ˆ 4.8, 9.5, 7.0 Hz, 1H), 5.22 (s, 1H),
5.46 (s, 1H), 6.92 (s, 1H); elemental analysis calcd (%) for C9H9NO3: C
60.33, H 5.06, N 7.82; found: C 60.15, H 4.99, N 7.72.
(Z)-5,5-Dimethyl-4-(2,2,3-trideuterio-3-pentadeuteriophenylcyclobutyli-
dene)-3-p-toluenesulfonyloxazolidin-2-one [(Z)-[D8]-7c]: 1H NMR
(400 MHz, CDCl3): d ˆ 1.56 (s, 3H), 1.57 (s, 3H), 2.45 (s, 3H), 2.95 (d,
Chem. Eur. J. 2003, 9, 2419 2438
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2433

Y. Tamaru et al.
FULL PAPER
‡
J ˆ 15.4 Hz, 1H), 3.29 (d, J ˆ 15.4 Hz, 1H), 7.34 (d, J ˆ 7.3 Hz, 2H), 7.94 (d,
C16H17NO6S: 351.0777; found: 351.0787 (33) [M] , 320(10), 196 (70), 164
J ˆ 7.3 Hz, 2H).[46]
(100).[17]
(Z)-5,5-Dimethyl-4-(cis-2-deuterio-3-phenylcyclobutylidene)-3-p-toluene-
sulfonyloxazolidin-2-one [(Z)-cis-[D1]-7c]: 1H NMR (400 MHz, CDCl3):
d ˆ 1.45 (s, 3H), 1.52 (s, 3H), 2.44 (s, 3H), 3.61 (q, J ˆ 8.7 Hz, 1H), 2.94
(ddd, J ˆ 2.6, 7.4, 15.2 Hz, 1H), 3.30 (ddd, J ˆ 2.6, 8.7, 15.2 Hz, 1H), 3.45
(brq, J ˆ 9.2 Hz, 1H), 7.14 7.29 (m, 5H), 7.34 (J ˆ 8.4 Hz, 2H), 7.97 (J ˆ
8.4 Hz, 2H).[46]
4-(3-Cyanocyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-one
(8b):
m.p. 107.5 108.08C (CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s), 1770 (s),
1720 (s), 1370 (s), 1260 (s), 1180 (s), 1120 (s), 1050 (s), 650 cmÀ1 (s);
1H NMR (400 MHz, CDCl3): d ˆ 2.46 (s, 3H), 2.94 3.05 (m, 2H), 3.25 (ddt,
J ˆ 7.0, 8.1, 9.2 Hz, 1H), 3.43 3.59 (m, 2H), 4.61 (m, 2H), 7.39 (d, J ˆ
8.6 Hz, 2H), 7.89 (d, J ˆ 8.6 Hz, 2H); HRMS: m/z (%): calcd for
‡
C15H14N2O4S: 318.0674; found: 318.0671 (27) [M] , 293 (15), 163 (14),
5,5-Dimethyl-4-(3-methyl-3-phenylcyclobutylidene)-3-p-toluenesulfonyl-
oxazolidin-2-one (7d): oil; IR (neat): n ˆ 1800 (s), 1720 (s), 1600 (s), 1490
(m), 1440 (m), 1370 (s), 1260 (s), 1170 (s), 1100 (m), 1080 (m), 980 cmÀ1 (m);
1H NMR (400 MHz, CDCl3): d ˆ 1.38 (s, 3H), 1.51 (s, 3H), 1.57 (s, 3H), 2.44
(s, 3H), 2.90 (dt, J ˆ 14.7, 2.8 Hz, 1H), 3.14 (dt, J ˆ 14.7, 2.8 Hz, 1H), 3.20
(dd, J ˆ 2.8, 14.7 Hz, 1H), 3.46 (dd, J ˆ 2.8, 14.7 Hz, 1H), 7.19 7.25 (m,
3H), 7.32 7.36 (m, 4H), 7.92 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd
155 (100); elemental analysis calcd (%) for C15H14N2O4S: C 56.59, H 4.43, N
8.80, S 10.07; found: C 56.72, H 4.39, N 8.58, S 9.95.
4-(3-Cyano-3-methylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-
one (8c): m.p. 149.8 150.88C (CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s),
1730 (s), 1370 (s), 1250 (s), 1170 (s), 1150 (s), 980 (s), 750 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 1.61 (s, 3H), 2.47 (s, 3H), 2.61 (dm, J ˆ 16.1 Hz,
1H), 3.14 (dm, J ˆ 16.1 Hz, 1H), 3.18 (dm, J ˆ 16.1 Hz, 1H), 3.64 (dm, J ˆ
16.1 Hz, 1H), 4.61 (brs, 2H), 7.38 (d, J ˆ 8.2 Hz, 2H), 7.90 (d, J ˆ 8.2 Hz,
2H); 13C NMR (100 MHz, CDCl3): d ˆ 21.8, 25.1, 27.7, 40.5, 43.9, 65.9, 110.2,
122.6, 124.1, 128.5, 130.0, 134.5, 146.2, 151.9; elemental analysis calcd (%)
for C16H16N2O4S: C 57.82, H 4.85, N 8.43, S 9.65; found: C 57.50, H 4.79, N
8.35, S 9.36.
‡
for C23H25NO4S: 411.1504; found: 411.1541 (4) [M] , 256 (100).[17]
5,5-Dimethyl-4-(3-trimethylsiloxy-3-phenylcyclobutylidene)-3-p-toluene-
sulfonyloxazolidin-2-one (7e): m.p. 71.0 72.08C (CH2Cl2/hexane); IR
(KBr): n ˆ 1780 (s), 1710 (m), 1380 (m), 1270 (m), 1180 (m), 1110 (m),
1
930 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 0.06 (s, 9H), 1.43 (s, 3H),
1.44 (s, 3H), 2.45 (s, 3H), 3.23 (dt, J ˆ 15.4 2.2 Hz, 1H), 3.28 (dd, J ˆ 2.2,
15.4 Hz, 1H), 3.49 (dd, J ˆ 2.2, 16.7 Hz, 1H), 3.64 (dt, J ˆ 16.7, 2.2 Hz, 1H),
7.29 7.39 (m, 5H), 7.45 (d, J ˆ 8.1 Hz, 2H), 7.92 (d, J ˆ 8.1 Hz, 2H);
HRMS: m/z (%): calcd for C25H31NO5SSi: 485.1692; found: 485.1666 (19)
(Z)-4-(3-Cyano-3-[D3]methyl-2,2-[D2]cyclobutylidene)-3-p-toluenesulfo-
nyloxazolidin-2-one [(Z)-[D5]-8c]: see ref. [17].
‡
[M] , 470(100); elemental analysis calcd (%) for C25H31NO5SSi: C 61.83, H
4-[3-(N,N-Dimethylcarbamoyl)cyclobutylidene]-3-p-toluenesulfonyloxa-
zolidin-2-one (8d): m.p. 158.1 158.98C (CH2Cl2/hexane); IR (KBr): n ˆ
1760 (s), 1730 (s), 1680 (s), 1385 (s), 1260 (s), 1190 (s), 1170 (s), 1140 (s),
1120 (s), 1060 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 2.67
(m, 1H), 2.97 (s, 3H), 2.98 (s, 3H), 3.10 (dm, J ˆ 15.1 Hz, 1H), 3.23 3.42
(m, 3H), 4.57 (dm, J ˆ 15.0 Hz, 1H), 4.64 (brd, J ˆ 15.0 Hz, 1H), 7.34 (d,
J ˆ 8.2 Hz, 2H), 7.90 (d, J ˆ 8.2 Hz, 2H); 13C NMR (100 MHz, CDCl3): d ˆ
21.7, 31.0, 33.1, 35.3, 35.6, 36.7, 66.2, 116.2, 119.8, 128.4, 130.0, 134.8, 145.8,
152.4, 173.0; HRMS: m/z (%): calcd for C17H20N2O5S: 364.1093; found:
6.43, N 2.88; found: C 61.85, H 6.44, N 2.81.[17]
(Z)-5,5-Dimethyl-4-(3-trimethylsiloxy-3-phenyl-2,2-[D2]cyclobutylidene)-
3-p-toluenesulfonyloxazolidin-2-one (7e): see ref. [17].
4-(3-Ethynyl-3-methylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-
one (7 f): oil; IR (neat): n ˆ 1782 (s), 1717 (m), 1600 (m), 1373 (s), 1263 (s),
1
1175 (m), 1090 (m), 1034 (m), 966 cmÀ1 (s); H NMR (400 MHz, CDCl3):
d ˆ 1.45 (s, 3H), 1.47 (s, 3H), 1.48 (s, 3H), 2.29 (s, 1H), 2.45 (s, 3H), 2.76
(ddd, J ˆ 1.8, 2.9, 15.0 Hz, 1H), 3.02 (ddd, J ˆ 1.8, 2.9, 16.3 Hz, 1H), 3.16
(dd, J ˆ 2.9, 15.0 Hz, 1H), 3.36 (dd, J ˆ 2.9, 16.3 Hz, 1H), 7.38 (d, J ˆ 8.4 Hz,
2H), 7.92 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for C19H21NO4S:
‡
364.1106 (5) [M] , 209 (100); elemental analysis calcd (%) for
C17H20N2O5S: C 56.03, H 5.53, N 7.69, S 8.80; found: C 55.61, H 5.40, N
7.48, S 8.63.
‡
359.1191; found: 359.1179 (17) [M] , 204 (100).[17]
5,5-Dimethyl-4-(3-phenylcyclobutylidene)-3-(2,2,2-trichloroethoxysulfo-
nyl)oxazolidin-2-one (7g): oil; IR (neat): n ˆ 1810 (s), 1720 (m), 1390 (m),
1370 (m), 1270 (s), 1200 (s), 1170 (m), 1120 (m), 1090 (m), 1000 (s),
860 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.51 (s, 3H), 1.57 (s, 3H),
2.89 (ddd, J ˆ 2.9, 7.5, 15.4 Hz, 1H), 3.14 (ddd, J ˆ2.9, 7.5, 16.7 Hz, 1H),
3.23 (ddt, J ˆ 9.2, 15.4, 2.9 Hz, 1H), 3.43 (ddt, J ˆ9.2, 16.7, 2.9 Hz, 1H), 3.57
(brtt, J ˆ 7.5, 9.2 Hz, 1H), 4.87 (d, J ˆ 11.4 Hz, 1H), 4.90 (d, J ˆ11.4 Hz,
1H), 7.13 7.28 (m, 5H); HRMS: m/z (%): calcd for C17H18NO5SCl3:
3-Benzoyl-4-(3-methoxycarbonylcyclobutylidene)oxazolidin-2-one (8e):
oil; IR (neat): n ˆ 1800 (s), 1750 (s), 1690 (s), 1370 (s), 1170 cmÀ1 (s);
1H NMR (400 MHz, CDCl3): d ˆ 2.86 (m, 1 H), 2.94 2.97 (m, 3H), 3.24 (tt,
J ˆ 7.6, 8.1 Hz, 1H), 3.69 (s, 3H), 4.83 (quint, J ˆ 2.6 Hz, 2H), 7.46 (t, J ˆ
8.1 Hz, 2H), 7.59 (t, J ˆ 8.1 Hz, 1H), 7.70 (d, J ˆ 8.1 Hz, 2H); elemental
analysis calcd (%) for C16H15NO5: C 63.78, H 5.02, N 4.65; found: C 63.38,
H 4.87, N 4.43.
‡
452.9984; found 452.9971 (2) [M] , 418(2), 198 (100).[17]
5,5-Dimethyl-4-(3-methoxycarbonylcyclobutylidene)-3-p-toluenesulfonyl-
oxazolidin-2-one (8 f): m.p. 71.0 72.08C (CH2Cl2/hexane); IR (KBr): n ˆ
1790 (s), 1730 (m), 1370 (s), 1260 (s), 1170 (s), 1110 (s), 840 cmÀ1 (w);
1H NMR (400 MHz, CDCl3): d ˆ 1.29 (t, J ˆ 7.2 Hz, 3H), 1.44 (s, 3H), 1.51
(s, 3H), 2.45 (s, 3H), 3.02 3.08 (m, 1H), 3.14 (dd, J ˆ 2.3, 6.3 Hz, 1H),
3.17 3.23 (m, 1H), 3.30 (ddd, J ˆ 2.3, 6.3, 16.8 Hz, 1H), 3.37 (m, 1H), 4.18
(q, J ˆ 7.2 Hz, 2H), 7.35 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz, 2H);
elemental analysis calcd (%) for C19H23NO6S: C 58.00, H 5.89, N 3.56, S
8.15; found: C 57.96, H 5.81, N 3.58, S 8.22.
(Z,E)-5,5-Dimethyl-4-(2-[D1]-3-ethyl-3-phenylcyclobutylidene)-3-p-tolue-
nesulfonyloxazolidin-2-one [(Z,E)-[D1]-7h]: oil; 1H NMR (400 MHz,
CDCl3): d ˆ 0.70 (t, J ˆ 7.3 Hz, 3H), 1.36 (s, 3H), 1.57 (s, 3H), 1.80 (q,
J ˆ 7.3 Hz, 2H), 2.44 (s, 3H), 2.93 (dd, J ˆ 2.9, 15.0 Hz, 1H), 3.14 (d, J ˆ
15.0 Hz, 1H), 3.38 (brs, 1H), 7.14 7.35 (m, 7H), 7.92 (d, J ˆ 8.4 Hz, 2H).[46]
4-(3-Methoxycarbonylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-
one (8a): CCDC-181560; m.p. 152.8 153.58C (CH2Cl2/hexane); IR (KBr):
1
n ˆ 1800 (s), 1790 (s), 1730 (s), 1370 (s), 1190 (s), 1160 cmÀ1 (s); H NMR
5,5-Dimethyl-4-(3-methoxycarbonyl-3-triisopropylsiloxycyclobutylidene)-
3-p-toluenesulfonyloxazolidin-2-one (8g): m.p. 112.5 113.08C (CH2Cl2/
hexane); IR (KBr): n ˆ 1790 (s), 1750 (s), 1720 (m), 1590 (w), 1460 (m),
1370 (s), 1270 (s), 1210 (m), 1190 (m), 1170 (m), 1120 (s), 990 cmÀ1 (m);
1H NMR (400 MHz, CDCl3): d ˆ 1.02 1.13 (m, 21H), 1.41 (s, 3H), 1.50 (s,
3H), 2.45 (s, 3H), 2.96 (dd, J ˆ 3.1, 15.4 Hz, 1H), 3.28 (dd, J ˆ 3.1, 16.9 Hz,
1H), 3.47 (dt, J ˆ 15.4 3.1 Hz, 1H), 3.60 (dt, J ˆ 16.9, 3.1 Hz, 1H), 3.76 (s,
3H), 7.35 (d, J ˆ 8.1 Hz, 2H), 7.90 (d, J ˆ 8.1 Hz, 2H); HRMS: m/z (%):
(400 MHz, CDCl3): d ˆ 2.46 (s, 3H), 2.77 (ddd, J ˆ 1.8, 9.1, 15.8 Hz, 1H),
2.92 (dm, J ˆ 15.8 Hz, 1H), 3.25 (tt, J ˆ 6.2, 9.2 Hz, 1H), 3.32 3.37 (m,
2H), 3.74 (s, 3H), 4.59 (dm, J ˆ 11.7 Hz, 1H), 4.64 (brd, J ˆ 11.7 Hz, 1H),
7.36 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3): d ˆ 21.7, 31.6, 33.9, 35.3, 52.0, 66.0, 115.5, 120.2, 128.4, 129.9, 134.9,
145.8, 152.3, 174.8; elemental analysis calcd (%) for C16H17NO6S; C 54.69,
H 4.88, N 3.99, S 9.13; found: C 54.57, H 4.82, N 4.03, S 9.00.
‡
4-[2-Oxo-3-p-toluenesulfonyl-2,3-dihydrooxazol-4-ylpent-4-enoic methyl
ester: The by-product appeared in run 3, Table 5): m.p. 114.0 114.58C
(CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s), 1740 (s), 1270 (s), 1200 (m),
calcd for C27H41NO7SSi: 508.1825 [M À iPr] ; found: 508.1820, 396 (100).
3-(2-Oxo-3-p-toluenesulfonyl-1-oxa-3-azaspiro[4.4]non-4-ylidene)cyclobu-
tanecarboxylic ethyl ester (8h): oil; IR (neat): n ˆ 1790 (s), 1730 (s), 1370
(s), 1260 (s), 1170 (s), 1090 (s), 810 (m), 750 cmÀ1 (m); 1H NMR (400 MHz,
CDCl3): d ˆ 1.28 (t, J ˆ 7.1 Hz, 3H), 1.70 2.10 (m, 8H), 2.45 (s, 3H), 3.02
(m, 1H), 3.14 (dm, J ˆ 13.0 Hz, 1H), 3.18 (dm, J ˆ 16.8 Hz, 1H), 3.32 (dm,
J ˆ 16.8 Hz, 1H), 3.39 (m, 1H), 4.18 (q, J ˆ 7.1 Hz, 1H), 7.35 (d, J ˆ 8.4 Hz,
1
1180 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 2.50 (t, J ˆ
7.5 Hz, 2H), 2.82 (t, J ˆ 7.5 Hz, 2H), 3.68 (s, 3H), 5.28 (brs, 1H), 5.34 (brs,
1H), 6.59 (s, 1H), 7.36 (d, J ˆ 8.4 Hz, 2H), 7.99 (d, J ˆ 8.4 Hz, 2H);
13C NMR (100 MHz, CDCl3): d ˆ 21.8, 30.4, 32.7, 51.7, 120.2, 126.4, 128.4,
128.6, 130.0, 133.6, 135.6, 146.5, 151.1, 172.8; HRMS: m/z (%): calcd for
2434
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
2H), 7.89 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for C21H25NO6S:
(400 MHz, CDCl3): d ˆ 2.45 (s, 3H), 2.55 (m, 1H), 2.82 (m, 1H), 3.03 (dm,
J ˆ 15.8 Hz, 1H), 3.24 (m, 1H), 3.32 (m, 1H), 4.46 4.68 (m, 2H), 6.36 (dd,
J ˆ 6.1, 15.8 Hz, 1H), 6.42 (d, J ˆ 15.8 Hz, 1H), 7.19 7.41 (m, 7H), 7.94 (d,
J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for C22H21NO4S: 395.1192; found:
‡
419.1402; found: 420.1476 (5) [M] , 374 (8), 264 (100).[17]
4-(3-Acetylcyclobutylidene)-3-p-toluenesulfonyl-1-oxa-3-azaspiro[4.4]-
nonan-2-one (8i): m.p. 83.0 84.08C (CH2Cl2/hexane); IR (KBr): n ˆ 1790
(s), 1720 (s), 1380 (s), 1340 (m), 1270 (s), 1180 (s), 1130 (m), 1090 (m), 910
(m), 730 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.65 2.08 (m, 8H),
2.17 (s, 3H), 2.45 (s, 3H), 2.88 (m, 1H), 3.16 (ddd, J ˆ 2.8, 6.6, 15.7 Hz, 1H),
3.22 (ddd, J ˆ 2.8, 6.6, 15.7 Hz, 1H), 3.32 (m, 1H), 3.41 (m, 1H), 7.35 (d, J ˆ
8.4 Hz, 2H), 7.88 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for
‡
395.1197 (11) [M] , 240 (40), 130 (100); elemental analysis calcd (%) for
C22H21NO4S: C 66.82, H 5.35, N 3.54, S 8.11; found: C 66.91, H 5.34, N 3.66,
S 7.99.
4-[3-trans-b-Styryl-3-(triisopropylsiloxy)cyclobutylidene]-3-p-toluenesul-
fonyloxazolidin-2-one (9d): m.p. 123.0 123.88C (CH2Cl2/hexane); IR
(KBr): n ˆ 1790 (s), 1725 (s), 1390 (m), 1365 (m), 1250 (m), 1190 (s), 1170
(m), 1135 (s), 1120 (s), 1090 (s), 990 (m), 960 (m), 875 cmÀ1 (m); 1H NMR
(400 MHz, CDCl3): d ˆ 1.00 1.13 (m, 21H), 2.44 (s, 3H), 2.81 (dm, J ˆ
15.6 Hz, 1H), 2.90 (dm, J ˆ 15.6 Hz, 1H), 3.32 (dm, J ˆ 16.9 Hz, 1H), 3.44
(dm, J ˆ 16.9 Hz, 1H), 4.59 (dm, J ˆ 11.9 Hz, 1H), 4.66 (dm, J ˆ 11.9 Hz,
1H), 6.41 (d, J ˆ 16.1 Hz, 1H), 6.57 (d, J ˆ 16.1 Hz, 1H), 7.31 7.38 (m, 5H),
7.34 (d, J ˆ 8.4 Hz, 2H), 7.92 (d, J ˆ 8.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3): d ˆ 3.3, 14.8, 20.9, 40.0, 72.6, 76.3, 118.7, 125.4, 126.5, 126.9, 127.7,
127.9, 128.4, 129.5, 129.6, 134.9, 136.3, 140.9, 153.9; HRMS: m/z (%): calcd
‡
C20H23NO5S: 389.1297; found: 390.1289 (100) [M] .[17]
3-(2-Oxo-3-p-toluenesulfonyl-1-oxa-3-aza-spiro[4.4]non-4-ylidene)cyclo-
butanecarbaldehyde (8j): m.p. 83.0 84.08C (CH2Cl2/hexane); IR (KBr):
n ˆ 1790 (s), 1720 (s), 1380 (s), 1270 (s), 1180 (s), 1120 (s), 1090 (s), 990 (m),
910 (m), 840 (m), 730 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.71 2.08
(m, 8H), 2.45 (s, 3H), 2.92 2.99 (m, 1H), 3.16 (ddd, J ˆ 2.5, 5.6, 15.7 Hz,
1H), 3.23 3.30 (m, 1H), 3.31 3.41 (m, 2H), 7.35 (d, J ˆ 8.4 Hz, 2H), 7.89
(d, J ˆ 8.4 Hz, 2H), 9.81 (d, J ˆ 1.5 Hz, 1H); HRMS: m/z (%): calcd for
‡
C19H21NO5S: 375.1140; found: 375.1122 (66) [M] , 331 (33), 220 (54), 176
‡
for C31H41NO5SSi: 567.2474; found: 567.2473 (14) [M] , 523 (14), 103 (41),
(100).[17]
91 (100).[17]
4-(3-Acetyl-3-methylcyclobutylidene)-3-p-toluenesulfonyl-1-oxa-3-aza-
spiro[4.4]nonan-2-one (8k): CCDC 179982; m.p. 136.0 136.98C (CH2Cl2/
hexane); IR (KBr): n ˆ 1780 (s), 1703 (s), 1383 (s), 1099 (s), 752 (s),
704 cmÀ1 (m); 1H NMR (400 MHz, CDCl3): d ˆ 1.45 (s, 3H), 1.66 2.12 (m,
8H), 2.18 (s, 3H), 2.45 (s, 3H), 2.49 (ddd, J ˆ 1.8, 2.9, 15.4 Hz, 1H), 2.98
(ddd, J ˆ 1.8, 2.9, 16.7 Hz, 1H), 3.30 (dd, J ˆ 3.2, 15.4 Hz, 1H), 3.37 (dd, J ˆ
3.2, 16.7 Hz, 1H), 7.35 (d, J ˆ 8.2 Hz, 2H), 7.88 (d, J ˆ 8.2 Hz, 2H); HRMS:
5,5-Dimethyl-4-(3-isopropenyl-3-methylcyclobutylidene)-3-p-toluenesul-
fonyloxazolidin-2-one (9e): oil; IR (neat): n ˆ 1790 (s), 1370 (s), 1270 (s),
1
1190 (s), 1170 (s), 1140 (m), 1090 (m), 990 cmÀ1 (m); H NMR (400 MHz,
CDCl3): d ˆ 1.30 (s, 3H), 1.39 (s, 3H), 1.53 (s, 3H), 1.73 (s, 3H), 2.44 (s,
3H), 2.55 (dt, J ˆ 14.6, 2.9 Hz, 1H), 2.77 (dt, J ˆ 16.0, 2.9 Hz, 1H), 2.93 (dd,
J ˆ 2.9, 14.6 Hz, 1H), 3.15 (dd, J ˆ 2.9, 16.0 Hz, 1H), 4.71 (s, 1H), 4.79 (t,
J ˆ 1.3 Hz, 1H), 7.34 (d, J ˆ 8.4 Hz, 2H), 7.91 (d, J ˆ 8.4 Hz, 2H); HRMS:
‡
m/z (%): calcd for C21H25NO5S: 403.1453; found: 403.1430 (34) [M] , 91
‡
m/z (%): calcd for C20H25NO4S: 375.15050; found: 375.1512 (12) [M] , 220
(100).[17]
(80), 206 (15), 176 (85), 160 (100); elemental analysis calcd (%) for
C20H25NO4S: C 63.98, H 6.71, N 3.73, S 8.54; found: C 63.63, H 7.06, N 3.36,
S 8.33.
1-Methyl-3-(2-oxo-3-p-toluenesulfonyl-1-oxa-3-azaspiro[4.4]non-4-ylide-
ne)cyclobutanecarbaldehyde (8l): IR (neat): n ˆ 1790 (s), 1720 (s), 1450
(m), 1370 (s), 1270 (s), 1170 (s), 1110 (m), 1090 (s), 990(m), 900 (s), 810 (m),
730 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.40 (s, 3H), 1.54 2.07 (m,
8H), 2.45 (s, 3H), 2.55 (dd, J ˆ 2.9, 15.4 Hz, 1H), 2.94 (dd, J ˆ 2.9, 16.9 Hz,
1H), 3.22 (dd, J ˆ 2.9, 15.4 Hz, 1H), 3.37 (dd, J ˆ 2.9, 16.9 Hz, 1H), 7.36 (d,
J ˆ 8.4 Hz, 2H), 7.88 (d, J ˆ 8.4 Hz, 2H), 9.67 (s, 1H); HRMS: m/z (%):
5,5-Dimethyl-4-(3-phenyl-3-vinylcyclobutylidene)-3-p-toluenesulfonyloxa-
zolidin-2-one (9 f): m.p. 49.0 50.58C (CH2Cl2/hexane); IR (KBr): n ˆ 1780
1
(s), 1370 (s), 1280 (s), 1260 (s), 1170 (s), 1115 (s), 900 cmÀ1 (m); H NMR
(400 MHz, CDCl3): d ˆ 1.32 (s, 3H), 1.35 (s, 3H), 2.45 (s, 3H), 2.69 (dd, J ˆ
6.6, 16.3 Hz, 1H), 3.41 (dm, J ˆ 20.0 Hz, 1H), 3.67 (dm, J ˆ 20.0 Hz, 1H),
3.75 (dm, J ˆ 16.3 Hz, 1H), 5.45 (dm, J ˆ 18.8 Hz, 2H), 6.15 (m, 1H), 7.22
7.37 (m, 7H), 7.98 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for
‡
calcd for C20H23NO5S: 389.1297; found: 389.1258 (66) [M] , 70 (100).[17]
3-(5-Methyl-2-oxo-3-p-toluenesulfonyloxazolidin-4-ylidene)cyclobutane-
carbaldehyde (8m): ꢀ1:1 mixture of stereoisomers: IR (neat): n ˆ 1778 (s),
‡
C24H25NO4S: 423.15050; found: 423.1514 (6) [M] , 268 (66), 182 (14), 154
1
1715 (s), 1339 (s), 758 cmÀ1 (m); H NMR (400 MHz, CDCl3) d ˆ 1.21 (d,
(11), 91 (100); elemental analysis calcd (%) for C24H25NO4S: C 68.06, H
5.95, N 3.31, S 7.57; found: C 68.15, H 5.88, N 3.29, S 7.63.
J ˆ 6.6 Hz, 3H, one isomer), 1.29 (d, J ˆ 6.2 Hz, 3H, the other isomer), 2.46
(s, 3H), 2.68 (ddm, J ˆ 8.6, 15.2 Hz, 1H, one isomer), 2.90 (m, 1H), 3.03
3.11 (m, 1H, one isomer), 3.12 3.21 (m, 2H), 3.25 3.54 (m, 2H), 4.93 (m,
1H), 7.36 (d, J ˆ 8.2 Hz, 2H), 7.89 (d, J ˆ 8.2 Hz, 2H, one isomer), 7.90 (d,
J ˆ 8.2 Hz, 2H, the other isomer), 9.82 (d, J ˆ 1.5 Hz, 1H, one isomer), 9.83
(d, J ˆ 1.5 Hz, 1H, the other isomer); HRMS: m/z (%): calcd for
5,5-Dimethyl-3-p-toluenesulfonyl-4-(3-trimethylsilylmethyl-3-vinylcyclo-
butylidene)oxazolidin-2-one (9g): oil; IR (neat): n ˆ 1790 (s), 1735 (m),
1360 (m), 1270 (m), 1190 (m), 1170 (m), 1120 (m), 1090 (m), 1035 (m), 910
1
(m), 850 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 0.01 (s, 9H), 1.05 (d,
J ˆ 14.3 Hz, 1H), 1.10 (d, J ˆ 14.3 Hz, 1H), 1.45 (s, 3H), 1.46 (s, 3H), 2.44 (s,
3H), 2.63 (dm, J ˆ 15.4 Hz, 1H), 2.83 (dm, J ˆ 16.9 Hz, 1H), 2.87 (dm, J ˆ
15.4 Hz, 1H), 3.07 (dm, J ˆ 16.9 Hz, 1H), 5.02 (dd, J ˆ 0.7, 17.7 Hz, 1H),
5.03 (dd, J ˆ 0.7, 10.2 Hz, 1H), 5.96 (dd, J ˆ 10.2, 17.7 Hz, 1H), 7.34 (d, J ˆ
8.1 Hz, 2H), 7.94 (d, J ˆ 8.1 Hz, 2H); HRMS: m/z (%): calcd for
‡
C16H17NO5S: 335.0827; found: 335.0836 (52) [M] , 180 (100).[17]
4-(3-Isopropenyl-3-methylcyclobutylidene)-3-p-toluenesulfonyloxazoli-
din-2-one (9a): oil; IR (neat): n ˆ 1800 (s), 1780 (m), 1380 (s), 1260 (s), 1180
(m), 1160 cmÀ1 (m); 1H NMR (400 MHz, CDCl3): d ˆ 1.23 (s, 3H), 1.66 (s,
3H), 2.16 (brd, J ˆ 14.7 Hz, 1H), 2.37 (s, 3H), 2.69 (dd, J ˆ 2.2, 14.7 Hz,
1H), 2.70 (dt, J ˆ 14.7, 2.2 Hz, 1H), 3.10 (dm, J ˆ 14.7 Hz, 1H), 4.48 (dm,
J ˆ 13.2 Hz, 1H), 4.58 (brd, J ˆ 13.2 Hz, 1H), 4.65 (s, 1H), 4.72 (s, 1H), 7.28
(d, J ˆ 8.1 Hz, 2H), 7.83 (d, J ˆ 8.1 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d ˆ 17.6, 20.6, 26.0, 38.8, 40.2, 41.8, 65.3, 107.6, 115.5, 119.2, 128.0, 128.7,
134.0, 144.6, 149.8, 151.6; HRMS: m/z (%): calcd for C18H21NO4S: 347.1191;
‡
C22H31NO4SSi: 433.1743; found 433.1743 (6) [M] , 91 (41), 73 (100).[17]
5,5-Dimethyl-4-(3-trans-b-styrylcyclobutylidene)-3-p-toluenesulfonyloxa-
zolidin-2-one (9h): m.p. 160.5 161.08C (CH2Cl2/hexane); IR (KBr): n ˆ
1800 (s), 1740 (m), 1380 (s), 1260 (s), 1180 (s), 1120 (s), 1090 (s), 980 cmÀ1
(m); 1H NMR (400 MHz, CDCl3): d ˆ 1.54 (s, 3H), 1.55 (s, 3H), 2.45 (s,
3H), 2.78 (ddd, J ˆ 2.9, 6.4, 15.7 Hz, 1H), 3.01 (ddd, J ˆ 2.9, 6.4, 15.7 Hz,
1H), 3.12 (ddd, J ˆ 2.9, 6.4, 11.8 Hz, 1H), 3.19 (m, 1H), 3.30 (ddt, J ˆ 2.9,
8.4, 15.7 Hz, 1H), 6.35 (dd, J ˆ 6.4, 15.8 Hz, 1H), 6.40 (d, J ˆ 15.8 Hz, 1H),
7.20 7.39 (m, 7H), 7.94 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for
‡
found 347.1193 (2) [M] , 193 (10), 192 (64), 132 (100).[17]
3-p-Toluenesulfonyl-4-[3-(trimethylsilylmethyl)-3-vinylcyclobutylide-
ne]oxazolidin-2-one (9b): oil; IR (neat): n ˆ 1789 (s), 1732 (s), 1373 (s),
1250 (s), 1175 (s), 1080 (m), 1050 (m), 950 cmÀ1 (s); 1H NMR (400 MHz,
CDCl3): d ˆ 0.01 (s, 9H), 1.06 (d, J ˆ 14.5 Hz, 1H), 1.10 (d, J ˆ 14.5 Hz,
1H), 2.37 (dm, J ˆ 15.0 Hz, 1H), 2.44 (s, 3H), 2.61 (dm, J ˆ 16.5 Hz, 1H),
2.85 (dm, J ˆ 16.5 Hz, 1H), 3.12 (dm, J ˆ 15.0 Hz, 1H), 4.56 4.60 (m, 2H),
5.00 (dd, J ˆ 1.1, 17.2 Hz, 1H), 5.02 (dd, J ˆ 1.1, 10.6 Hz, 1H), 5.97 (dd, J ˆ
10.6, 17.2 Hz, 1H), 7.34 (d, J ˆ 8.3 Hz, 2H), 7.90 (d, J ˆ 8.3 Hz, 2H); HRMS:
m/z (%): calcd for C20H27NO4SSi À Me: 390.1195; found: 390.1203 (2)
‡
C24H25NO4S: 423.15050; found: 423.1514 (8) [M] , 270 (13), 267 (12), 210
(13), 91 (100); elemental analysis calcd (%) for C24H25NO4S: C 68.06, H
5.95, N 3.31, S 7.57; found: C 67.63, H 5.94, N 3.09, S 7.19.
5,5-Dimethyl-3-p-toluenesulfonyl-4-[3-(trans-2-triisopropylsiloxyvinyl)cy-
clobutylidene]oxazolidin-2-one (9i): m.p. 102.8 104.08C (CH2Cl2/hex-
ane); IR (KBr): n ˆ 1790 (s), 1660 (m), 1370 (m), 1270 (s), 1210 (m),
1
1170 (s), 1110 (m), 1080 (m), 910 cmÀ1 (m); H NMR (400 MHz, CDCl3):
‡
[M À Me] , 250 (42), 91 (39), 73 (100).[17]
d ˆ 1.04 1.15 (m, 21H), 1.42 (s, 3H), 1.50 (s, 3H), 2.44 (s, 3H), 2.59 (ddd,
J ˆ 2.6, 6.8, 14.7 Hz, 1H), 2.81 (ddd, J ˆ 2.6, 6.8, 15.4 Hz, 1H), 2.90 (dtt, J ˆ
8.6, 6.8, 8.2 Hz, 1H), 3.02 (ddt, J ˆ 8.2, 14.7, 2.6 Hz, 1H), 3.21 (ddt, J ˆ 8.2,
15.4, 2.6 Hz, 1H), 5.17 (dd, J ˆ 8.6, 12.1 Hz, 1H), 6.37 (d, J ˆ 12.1 Hz, 1H),
4-(3-trans-b-Styrylcyclobutylidene)-3-p-toluenesulfonyloxazolidin-2-one
(9c): m.p. 59.0 59.58C (CH2Cl2/hexane); IR (KBr): n ˆ 1780 (s), 1370 (s),
1260 (s), 1170 (s), 1110 (s), 1090 (s), 900 (s), 750 cmÀ1 (m); 1H NMR
Chem. Eur. J. 2003, 9, 2419 2438
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2435

Y. Tamaru et al.
FULL PAPER
‡
7.33 (d, J ˆ 8.1 Hz, 2H), 7.92 (d, J ˆ 8.1 Hz, 2H); HRMS: m/z (%): calcd for
[M] , 91 (24), 73 (100); elemental analysis calcd (%) for C22H31NO4SSi: C
‡
C27H41NO5SSi À iPr: 476.1927; found: 476.1917 (4) [M À iPr] , 364 (100);
60.93, H 7.21, N 3.23; found: C 60.90, H 7.11, N 3.20.
elemental analysis calcd (%) for C27H41NO5SSi: C 62.39, H 7.95, N 2.69;
found: C 63.30, H 7.85, N 2.80.
8-Methyl-11-methylene-12-p-toluenesulfonyl-7,14-dioxa-12-azadispiro-
[4.0.5.3]tetradec-8-en-13-one (10a): m.p. 192.0 193.08C (CH2Cl2/hexane);
IR (KBr): n ˆ 1790 (s), 1380 (m), 1260 (m), 1180 (s), 1140 (m), 1040 cmÀ1
4-[3-(trans-2-Methoxyvinyl)cyclobutylidene]-5,5-dimethyl-3-(p-toluene-
sulfonyl)oxazolidin-2-one (9j): m.p. 87.7 88.38C (CH2Cl2/hexane); IR
(KBr): n ˆ 1815 (s), 1390 (s), 1275 (s), 1220 (m), 1205 (m), 1190 (s), 1155
(m), 990 (m), 760 cmÀ1 (m); 1H NMR (400 MHz, CDCl3): d ˆ 1.43 (s, 3H),
1.51 (s, 3H), 2.45 (s, 3H), 2.61 (ddd, J ˆ 2.9, 6.6, 15.0 Hz, 1H), 2.84 (ddd, J ˆ
2.9, 6.6, 15.8 Hz, 1H), 2.93 (brtq, J ˆ 6.6, 8.4 Hz, 1H), 3.04 (ddt, J ˆ 8.4,
15.0, 2.9 Hz, 1H), 3.21 (ddt, J ˆ 8.4, 15.8, 2.9 Hz, 1H), 3.53 (s, 3H), 4.89 (dd,
J ˆ 8.4, 12.5 Hz, 1H), 6.34 (d, J ˆ 12.5 Hz, 1H), 7.34 (d, J ˆ 8.1 Hz, 2H), 7.92
(d, J ˆ 8.1 Hz, 2H); HRMS: m/z (%): calcd for C19H23NO5S: 377.1297;
1
(m); H NMR (400 MHz, CDCl3): d ˆ 1.26 1.93 (m, 8H), 1.86 (brs, 3H),
2.44 (s, 3H), 2.79 (dquint, J ˆ 19.8, 2.6 Hz, 1H), 2.99 (dd, J ˆ 5.0, 19.8 Hz,
1H), 4.65 (d, J ˆ 5.0 Hz, 1H), 5.44 (d, J ˆ 2.6 Hz, 1H), 5.56 (d, J ˆ 2.6 Hz,
1H), 7.31 (d, J ˆ 8.2 Hz, 2H), 8.02 (d, J ˆ 8.2 Hz, 2H); elemental analysis
calcd (%) for C20H23NO5S: C 61.68, H 5.95, N 3.60, S 8.23; found: C 61.37, H
5.86, N 3.46, S 8.02.
11-Methylene-12-p-toluenesulfonyl-7,14-dioxa-12-aza-dispiro[4.0.5.3]te-
tradec-8-en-13-one (10b): m.p. 157.5 158.58C (CH2Cl2/hexane); IR (KBr):
n ˆ 1790 (s), 1680 (m), 1370 (s), 1340 (s), 1310 (m), 1270 (s), 1230 (s), 1180
(s), 1150 (m), 1090 (s), 1070 (s), 1040 (s), 980 (m), 910 cmÀ1 (m); 1H NMR
(400 MHz, CDCl3): d ˆ 1.65 1.94 (m, 8H), 2.44 (s, 3H), 2.82 (ddm, J ˆ 2.6,
20.1 Hz, 1H), 3.03 (dd, J ˆ 6.0, 20.1 Hz, 1H), 4.93 (dt, J ˆ 1.8, 6.0 Hz, 1H),
5.48 (d, J ˆ 2.6 Hz, 1H), 5.59 (d, J ˆ 2.6 Hz, 1H), 6.47 (ddm, J ˆ 1.8, 6.0 Hz,
1H), 7.32 (d, J ˆ 8.4 Hz, 2H), 7.99 (d, J ˆ 8.4 Hz, 2H); HRMS: m/z (%):
‡
found: 377.1333 (1) [M] , 222 (100).[17]
5,5-Dimethyl-3-p-toluenesulfonyl-4-[3-(triisopropylsiloxy)-3-vinylcyclobu-
tylidene]oxazolidin-2-one (9k): m.p. 138.0 139.08C (CH2Cl2/hexane); IR
(KBr):n ˆ 1780 (s), 1370 (s), 1275 (s), 1120 cmÀ1 (s); 1H NMR (400 MHz,
CDCl3): d ˆ 1.01 1.10 (m, 21H), 1.40 (s, 3H), 1.50 (s, 3H), 2.44 (s, 3H), 2.98
(brd, J ˆ 15.0 Hz, 1H), 3.02 (brd, J ˆ 15.0 Hz, 1H), 3.20 (brd, J ˆ 17.0 Hz,
1H), 3.29 (brd, J ˆ 17.0 Hz, 1H), 5.06 (dd, J ˆ 1.1, 10.6 Hz, 1H), 5.24(dd,
J ˆ 1.1, 17.4 Hz, 1H), 6.07 (dd, J ˆ 10.6, 17.4 Hz, 1H), 7.34 (d, J ˆ 8.2 Hz,
1H), 7.90 (d, J ˆ 8.2 Hz, 1H); 13C NMR (100 MHz, CDCl3): d ˆ 13.3, 18.2,
21.7, 25.2, 26.0, 45.3, 47.5, 72.8, 84.2, 111.9, 114.7, 128.3, 129.7, 130.2, 135.4,
142.5, 145.5, 151.4; HRMS: m/z (%): calcd for C27H41NO5SSi: 519.2475;
‡
calcd for C19H21NO5S: 375.1140; found 375.1160 (12) [M] , 221 (11), 176
(100).[17]
8,9-Dimethyl-11-methylene-12-p-toluenesulfonyl-7,14-dioxa-12-azadispiro-
[4.0.5.3]tetradec-8-en-13-one (10c): m.p. 212.0 212.38C (CH2Cl2/hexane);
IR (KBr): n ˆ 1778 (s), 1713 (m), 1377 (s), 1335 (m), 1232 (m), 1159 (s),
1124 (m), 1086 (m), 1061 cmÀ1 (s); 1H NMR (400 MHz, CDCl3): d ˆ 1.65
1.91 (m, 8H), 1.65 (s, 3H), 1.84 (s, 3H), 2.44 (s, 3H), 2.77 (d, J ˆ 19.4 Hz,
1H), 2.85 (d, J ˆ 19.4 Hz, 1H), 5.40 (d, J ˆ 2.6 Hz, 1H), 5.53 (d, J ˆ 2.6 Hz,
1H), 7.31 (d, J ˆ 8.2 Hz, 2H), 8.02 (d, J ˆ 8.2 Hz, 2H); HRMS: m/z (%):
calcd for C21H25NO5S: 403.1453; found: 403.1433 (20), 248 (100).[17]
‡
found 519.2417 (2) [M] , 364 (100); elemental analysis calcd (%) for
C27H41NO5SSi: C 62.39, H 7.95, N 2.69; found: C 62.14, H 7.85, N 2.70.
5,5-Dimethyl-4-[3-trans-b-styryl-3-(triisopropylsiloxy)cyclobutylidene]-3-
p-toluenesulfonyl-oxazolidin-2-one (9l): oil; IR (neat): n ˆ 1790 (s), 1370
(m), 1260 (m), 1190 (m), 1170 (m), 1115 (m), 1085 (m), 1010 (m), 990 (s),
1
960 (m), 875 (m), 805 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 1.08 (s,
9-Methyl-11-methylene-12-p-toluenesulfonyl-7,14-dioxa-12-aza-dispiro-
[4.0.5.3]tetradec-8-en-13-one (10d): m.p. 109.0 110.08C (CH2Cl2/hexane);
IR (KBr): n ˆ 1790 (s), 1700 (m), 1370 (s), 1330 (m), 1310 (m), 1260 (m),
1180 (s), 1150 (s), 1090 (m), 1040 (s), 940 cmÀ1 (m); 1H NMR (400 MHz,
CDCl3): d ˆ 1.56 (s, 3H), 1.61 1.90 (m, 8H), 2.44 (s, 3H), 2.78 (dm, J ˆ
20.5 Hz, 1H), 2.88 (dm, J ˆ 20.5 Hz, 1H), 5.46 (d, J ˆ 2.2 Hz, 1H), 5.57 (d,
J ˆ 2.2 Hz, 1H), 6.27 (t, J ˆ 1.1 Hz, 1H), 7.31 (d, J ˆ 8.4 Hz, 2H), 7.98 (d,
J ˆ 8.4 Hz, 2H); HRMS: m/z (%): calcd for C20H23NO5S: 389.1297; found:
21H), 1.42 (s, 3H), 1.49 (s, 3H), 2.43 (s, 3H), 3.08 (brd, J ˆ 14.3 Hz, 1H),
3.12 (brd, J ˆ 14.3 Hz, 1H), 3.30 (brd, J ˆ 16.7 Hz, 1H), 3.42 (brd, J ˆ
16.7 Hz, 1H), 6.42 (d, J ˆ 15.9 Hz, 1H), 6.61 (d, J ˆ 15.9 Hz, 1H), 6.40 6.63
(m, 2H), 7.31 7.39 (m, 5H), 7.92 (d, J ˆ 8.4 Hz, 1H); HRMS: m/z (%):
‡
calcd for C33H45NO5SSi: 595.2788; found: 595.2821 (2) [M] , 440 (100).
4-[3-Isopropenyl3-(triisopropylsiloxy)cyclobutylidene]-5,5-dimethyl-3-p-
toluenesulfonyloxazolidin-2-one (9m): m.p. 118.0 118.28C (CH2Cl2/hex-
ane); IR (KBr): n ˆ 1782 (s), 1369 (s), 1275 (s), 1120 cmÀ1 (s); 1H NMR
(400 MHz, CDCl3): d ˆ 1.00 1.09 (m, 21H), 1.40 (s, 3H), 1.47 (s, 3H), 1.81
(brs, 3H), 2.45 (s, 3H), 2.94 (dd, J ˆ 2.9, 15.2 Hz, 1H), 3.07 (dt, J ˆ 15.2,
2.9 Hz, 1H), 3.14 (dd, J ˆ 2.9, 16.9 Hz, 1H), 3.44 (dt, J ˆ 16.9. 2.9 Hz, 1H),
4.84 (t, J ˆ 1.5 Hz, 1H), 4.96 (brs, 1H), 7.34 (d, J ˆ 8.1 Hz, 2H), 7.90 (d, J ˆ
8.1 Hz, 2H); HRMS: m/z (%): calcd for C28H43NO5SSi: 533.2631; found:
389.1293 (18) [M] , 234 (68), 190 (100).[17]
‡
4-Methyl-10-methylene-1-(p-toluenesulfonyl)-3,6-dioxa-1-azaspiro[4.5]-
dec-7-en-2-one (10e): ꢀ1:1.2 mixture of stereoisomers): m.p. 113.0
114.58C; IR (KBr): n ˆ 1786 (s), 1375 (s), 1177 (s), 762 (m), 704 cmÀ1
(m); 1H NMR (400 MHz, CDCl3): d ˆ 1.26 (d, J ˆ 6.6 Hz, 3H, major
isomer), 1.35 (d, J ˆ 6.4 Hz, 3H, minor isomer), 2.44 (s, 3H), 2.87 (dm, J ˆ
19.8 Hz, 1H, minor isomer), 2.91 (dm, J ˆ 19.8 Hz, 1H, major isomer), 3.07
(dm, J ˆ 19.8 Hz, 1H, major isomer), 3.09 (dm, J ˆ 19.8 Hz, 1H, minor
isomer), 4.40 (q, J ˆ 6.4 Hz, 1H, minor isomer), 4.52 (q, J ˆ 6.6 Hz, 1H,
major isomer), 4.96 (m, 1H), 5.40 (brs, 1H, minor isomer), 5.53 (m, 1H,
major isomer), 5.58 (m, 1H), 6.41 (dm, J ˆ 5.7 Hz, 1H, major isomer), 6.46
(dm, J ˆ 5.7 Hz, 1H, minor isomer), 7.33 (d, J ˆ 8.2 Hz, 2H), 7.98 (d, J ˆ
8.2 Hz, 2H, minor isomer), 8.00 (d, J ˆ 8.2 Hz, 2H, major isomer); HRMS:
‡
533.2594 (14) [M] , 91 (100); elemental analysis calcd (%) for C28H43NO5S-
Si: C 63.00, H 8.12, N 2.62; found: C 62.65, H 8.06, N 2.75.
4-(3-Isopropenyl-3-methylcyclobutylidene)-3-p-toluenesulfonyl-1-oxa-3-
azaspiro[4.4]nonan-2-one (9n): m.p. 106.0 107.08C (CH2Cl2/hexane); IR
(KBr): n ˆ 1790 (s), 1370 (s), 1280 (m), 1170 (s), 1110 (w), 880 cmÀ1 (w);
1H NMR (400 MHz, CDCl3): d ˆ 1.30 (s, 3H), 1.73 (brs, 3H), 1.59 2.18 (m,
8H), 2.44 (s, 3H), 2.52 (dt, J ˆ 14.5, 3.0 Hz, 1H), 2.81 (dt, J ˆ 16.1, 3.0 Hz,
1H), 2.91 (dd, J ˆ 3.0, 14.5 Hz, 1H), 3.19 (dd, J ˆ 3.0, 16.1 Hz, 1H), 4.71 (s,
1H), 4.79 (brs, 1H), 7.43 (d, J ˆ 8.2 Hz, 2H), 7.88 (d, J ˆ 8.2 Hz, 2H);
HRMS: m/z (%): calcd for C22H27NO4S: 401.1661; found: 401.1661 (2)
‡
m/z (%): calcd for C16H17NO5S: 335.0827; found 335.0836 (17) [M] , 180
(52), 91 (100).[17]
4-Methylene-6-p-toluenesulfonyl-3-(2,4,6-trimethylphenyl)-1,8-dioxa-2,6-
diazaspiro[4.4]non-2-en-7-one (11a): m.p. 252.0 253.08C (CH2Cl2/hex-
ane); IR (KBr): n ˆ 1790 (s), 1660 (s), 1370 (m), 1250 (m), 1230 (m), 1050
‡
[M] , 357 (17), 246 (35), 202 (100); elemental analysis calcd (%) for
(m), 850 cmÀ1 (m); H NMR (400 MHz, CDCl3): d ˆ 2.32 (s, 3H), 2.39 (s,
C22H27NO4S: C 65.81, H 6.78, N 3.49, S 7.99; found: C 65.91, H 6.69, N 3.40,
S 8.11.
1
6H), 2.43 (s, 3H), 4.35 (d, J ˆ 9.2 Hz, 1H), 4.43 (d, J ˆ 9.2 Hz, 1H), 5.28 (s,
1H), 6.94 (s, 1H), 6.69 (s, 2H), 7.30 (d, J ˆ 8.4 Hz, 2H), 7.90 (d, J ˆ 8.4 Hz,
2H); HRMS: m/z (%): calcd for C22H22N2O5S: 426.1249; found: 426.1242
5,5-Dimethyl-3-(p-toluenesulfonyl)-4-{3-[3-trans-(trimethylsilyl)prope-
nyl]cyclobutylidene}oxazolidin-2-one (9o): m.p. 86.5 87.58C (CH2Cl2/
‡
(6) [M] , 271 (100); elemental analysis calcd (%) for C22H22N2O5S: C 61.96,
H 5.20, N 6.57, S 7.52; found: C 61.86, H 5.25, N 6.47, S 7.66.
1
hexane); IR (KBr): n ˆ 1790(s), 1371 (s), 1177 (s), 858 cmÀ1 (s); H NMR
(400 MHz, C6D6): d ˆ 0.04 (s, 9H), 1.08 (s, 3H), 1.14 (s, 3H), 1.46 (d, J ˆ
8.1 Hz, 2H), 1.84 (s, 3H), 2.35 (ddd, J ˆ 2.9, 7.0, 15.2 Hz, 1H), 2.71 (ddt, J ˆ
8.1, 15.2, 2.9 Hz, 1H), 3.04 (ddd, J ˆ 2.9, 7.0, 15.6 Hz, 1H), 3.12 (ttm, J ˆ 7.0,
8.1 Hz, 1H), 3.45 (ddt, J ˆ 8.1, 15.6, 2.9 Hz, 1H), 5.42 (dt, J ˆ 10.6, 8.1 Hz,
1H), 5.48 (dd, J ˆ 8.1, 10.6 Hz, 1H), 6.75 (d, J ˆ 8.2 Hz, 2H), 8.11 (d, J ˆ
8.2 Hz, 2H); 13C NMR (100 MHz, CDCl3): d ˆ 1.25, 22.2, 24.3, 28.1, 28.6,
32.0, 39.8, 43.2, 87.1. 123.9, 128.9, 132.1, 132.7, 135.3, 139.6, 148.1, 154.7;
HRMS: m/z (%): calcd for C22H31NO4SSi: 433.1743; found: 433.1744 (35)
9,9-Dimethyl-4-methylene-6-p-toluenesulfonyl-3-(2,4,6-trimethylphenyl)-
1,8-dioxa-2,6-diaza-spiro[4.4]non-2-en-7-one (11b): m.p. 199.0 200.08C
(CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s), 1630 (m), 1380 (m), 1190 (m),
1180 (m), 1150 (m), 1140 (m), 1090 (m), 970 cmÀ1 (m); 1H NMR (400 MHz,
CDCl3): d ˆ 1.48 (s, 3H), 1.49 (s, 3H), 2.13 (s, 3H), 2.34 (s, 3H), 2.41 (s, 3H),
2.45 (s, 3H), 5.57 (d, J ˆ 1.5 Hz, 1H), 5.78 (d, J ˆ 1.5 Hz, 1H), 6.93 (s, 1H),
7.00 (s, 3H), 7.35 (d, J ˆ 8.6 Hz, 2H), 8.05 (d, J ˆ 8.6 Hz, 2H); elemental
2436
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 2419 2438

Unique Thermal Cycloadditions
2419 2438
analysis calcd (%) for C24H26N2O5S: C 63.42, H 5.77, N 6.16, S 7.05; found: C
63.28, H 5.80, N 6.06, S 6.81.
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4-Methylene-13-p-toluenesulfonyl-3-(2,4,6-trimethylphenyl)-1,11-dioxa-
2,3-diazadispiro[4.0.4.3]tridec-2-en-12-one (11c): m.p. 190.5 191.08C
(CH2Cl2/hexane); IR (KBr): n ˆ 1800 (s), 1630 (m), 1440 (m), 1380 (m),
1190 (m), 1150 (m), 1090 (m), 970 cmÀ1 (m); 1H NMR (400 MHz, CDCl3):
d ˆ 1.57 1.94 (m, 8H), 2.10 (s, 3H), 2.34 (s, 3H), 2.41 (s, 3H), 2.45 (s, 3H),
5.59 (d, J ˆ 1.3 Hz, 1H), 5.73 (d, J ˆ 1.3 Hz, 1H), 6.93 (s, 1H), 7.00 (s, 1H),
7.35 (d, J ˆ 8.6 Hz, 1H), 7.97 (d, J ˆ 8.6 Hz, 1H); 13C NMR (100 MHz,
CDCl3): d ˆ 19.6, 20.1, 21.1, 21.8, 22.0, 22.8, 23.6, 33.3, 34.5, 51.1, 97.1, 101.3,
119.5, 122.8, 128.5, 129.1, 129.5, 129.8, 134.7, 136.8, 138.8, 139.8, 143.1, 145.8,
150.7, 159.8; elemental analysis calcd (%) for C26H28N2O5S: C 64.98, H 5.87,
N 5.83, S 6.67; found: C 64.91, H 5.88, N 5.80, S 7.00.
Acknowledgement
We thankMr. Y. Ohhama (400 MHz 1H NMR measurements, Nagasaki
Univ.) and Dr. H. Kawano (X-ray structure analysis, NU). We also thank
Dr. S. Kanemasa (Institute of Advanced Material Study, Kyushu Univer-
sity) for his helpful guidance for the treatment of nitrile oxides and Mr. Y.
Wakamiya, Mr. K. Odaka, and Mr. M. Mori (NU) for their technical
assistance. a-Methylacryloyl isocyanate and chlorobutadienes were a gift
from Nippon Paint Co. and Tosoh Corp., respectively. This research has
been supported by the Ministry of Education, Science, Sports and Culture,
Japanese Government, Grant-in-Aid for Scientific Research B.
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www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2437

Y. Tamaru et al.
FULL PAPER
2001, 7, 1209 1220; matrix-isolated cyclohepta-1,2,4,6-tetraene: o) S.
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[17] 1H NMR spectrum of this compound is compiled in the Supporting
Information.
[18] CCDC-181558 (2a), -181724 (2b), -188289 (2g), -181726 (2k), -
181555 (2m), -181553 (2n), -181554 (2p), -181559 (2q), -181551 (7c),
-181560 (8a), -179982 (8k) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ,
UK; (fax: (‡44)1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk).
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Received: November 19, 2002 [F4586]
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