Carbene reactions of α-oxacyclo- and α-azacyclo-N-aziridinylimines: Effect of heteroatom and ring size in the ring expansion reaction

Article abstract of DOI:10.1055/s-2000-7598

Carbenes, generated from thermolysis of α-oxacyclo- and α-azacyclo-N-aziridinylimines in refluxing toluene, underwent ring expansions via insertion of alkyl carbenes into carbon-carbon bonds and intramolecular ammonium ylide formations, respectively. Ring expansion reaction of α-oxetanyl-N-aziridinylimines occurred via alkylidenecarbene intermediates, whereas thermal reaction of α-azetidinyl-N-aziridinylimines afforded α-aminoacetylene compounds via 1,2-H migration of alkylidenecarbene intermediates.

Full text of DOI:10.1055/s-2000-7598

1622
FEATURE ARTICLE
Carbene Reactions of a-Oxacyclo- and a-Azacyclo-N-aziridinylimines: Effect
of Heteroatom and Ring Size in the Ring Expansion Reaction
Sunggak Kim,* Joo-Yong Yoon
Department of Chemistry and Center for Molecular Design and Synthesis, School of Molecular Science (BK21), Korea Advanced Institute
of Science and Technology, Taejon 305-701, Korea
Fax +82(42)8698370; E-mail: skim@mail.kaist.ac.kr
Received 11 May 2000
nylimines in refluxing toluene generated b-hydroxyalky-
Abstract: Carbenes, generated from thermolysis of a-oxacyclo-
lidene carbenes, which underwent 1,5-C-H insertion16
and a-azacyclo-N-aziridinylimines in refluxing toluene, underwent
and 1,5-O-Si insertion17 to afford cyclopentenols and di-
ring expansions via insertion of alkyl carbenes into carbon-carbon
hydrofurans, respectively. As an extension of this work,
bonds and intramolecular ammonium ylide formations, respective-
ly. Ring expansion reaction of a-oxetanyl-N-aziridinylimines oc- we also reported that the thermolysis of a-thia-N-aziridi-
nylimines proceeded via sulfur ylide intermediates.18 Our
curred via alkylidenecarbene intermediates, whereas thermal
reaction of a-azetidinyl-N-aziridinylimines afforded a-aminoacet-
next attention was given to a-oxacyclo and a-azacyclo-N-
ylene compounds via 1,2-H migration of alkylidenecarbene inter-
aziridinylimines to examine the effect of oxygen and ni-
mediates.
trogen along with ring size of a-heterocycles in the ring
expansion reactions.
Key words: carbenes, heterocycles, hydrazones, ring expansions,
ylides
O
O
O
CH
R
N
N
path c
Singlet carbenes, in particular, can function as Lewis ac-
ids by interacting with a pair of non-bonding electrons
contributed by a Lewis base.1 If the Lewis base is an un-
charged species, the outcome of such an acid-base reac-
tion is an ylide. Nucleophilic species that are known to
trap carbenes include ethers, thioethers, amines, and ha-
lides. Compounds containing heteroatoms in the sp2 or in
the sp state of hybridization interact similarly with car-
benes. Examples of such functional groups include alde-
hydes, esters, ketones, imines, thiocarbonyl compounds,
and nitriles. 2
n
R
R
n
Ph
n
3
2
1a: n = 1
1c: n = 3
1b: n = 2
path b
path a
O
O
HO
R
6a: 59%
n
R
n
n
R
4
5b: 68%
5c:
6
R = CH2CH2Ph
69%
Scheme 1
Among these ylides, the chemistry of sulfur ylides has
been the subject of extensive research, largely because of
their easy preparation and the interesting rearrangements
which they often undergo.3 A large variety of sulfur com-
pounds, including cyclic and acyclic alkyl and aryl sul-
fides, are known to trap carbenes to form sulfur ylides.
These ylides become increasingly useful in organic syn-
thesis and evidence also exists for their involvement in
biochemical processes.4 In contrast to sulfur ylides, oxo-
nium ylides have been postulated as intermediates when
diazo compounds decompose in the presence of 1,3-diox-
olanes,5 styrene oxide,6 allylic ethers7 and oxetanes.8 Car-
benoids react with the oxygen of epoxides9 and
sulfoxides10 effecting transfer of oxygen to the carbene
center to form oxonium ylides. Oxonium ylides have also
been generated by deprotonation and desilylation of oxo-
nium ions.11
The reaction of oxetanes with alkoxycarbonyl carbenes
has been previously studied and the reaction was known
to proceed via competitive oxonium ylide formation and
C-H insertion.19 However, with tetrahydrofuran, car-
benes reacted to give only C-H insertion products.20 In
thermal reaction of a-oxacyclo-N-aziridinyl imines, we
were interested in whether (i) the reaction would involve
carbene 2 or alkylidenecarbene 4 (path a) and (ii) carbene
2 would undergo insertion into carbon-carbon bond to af-
ford 5 (path b) or oxonium ylide formation to afford 6
(path c) as shown in Scheme 1.21
Thermal reaction of a-oxetanyl-N-aziridinylimine 1a in
refluxing toluene for 5 hours gave dihydrofuran 6a in
59% yield, indicating that the reaction must involve alkyl-
idenecarbene 4 and the subsequent 1,5-O-H insertion
probably because of the relief of an oxetane ring strain and
the difficulty of the formation of a highly strained oxoni-
um ylide intermediate 3a. However, when the thermal re-
action of a-tetrahydrofuranyl derivative 1b was carried
out in refluxing toluene for 5 hours, 5b was isolated in
68% yield. This result is in contrast with the previous
Since Eschenmoser reported that N-aziridinylimines of
a,b-epoxy ketones underwent thermal fragmentation,12 N-
aziridinylimines have been utilized as precursors of both
diazoalkanes13 and carbenes.14 In connection with our in-
terest in the synthetic utility of N-aziridinylimines,15 we
found that thermal reaction of a,b-epoxy-N-aziridi-
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

FEATURE ARTICLE
Carbene Reactions of a-Oxacyclo- and a-Azacyclo-N-aziridinylimines
1623
R
result obtained with 1a. Apparently, the ring expansion
occurred via insertion of carbene 2b into carbon-carbon
bond. A similar result was also obtained with a-tetrahy-
dropyranyl-N-aziridinylimines. Thus, it is evident that the
thermal reaction of a-oxacyclo-N-aziridinylimines pro-
ceeds through two different pathways and depends on the
ring size of the oxacycles. The thermal reaction of highly
strained epoxy and oxetanyl derivatives proceeds via
alkylidenecarbene intermediates 4 due to relief of ring
strain, whereas relatively stable tetrahydrofuranyl and tet-
rahydropyranyl derivatives undergo ring expansion via
O
Ph
bond a
migration
R
R
CH
N N
O
O
9: 72%
cis/trans = 10/1
a
b
H
H
R
bond b
migration
O
8
7 cis/trans = 10/1
R = PhCH2
10
Scheme 2
carbene intermediates 2. Several experimental results are To study the efficiency of ring expansion process of a-ox-
summarized in Table 1. In the case of a-oxetanyl-N-aziri- acyclo-N-aziridinylimines, competition experiments were
dinylimines, the oxetane ring underwent ring expansion carried out with a-oxetanyl derivative 18 and a-tetrahy-
(Entries 1, 2, and 3), whereas the carbocyclic ring under- dropyranyl derivative 21 (Scheme 3). To examine the
went ring expansion in a-tetrahydrofuranyl (Entries 4 and competition between 1,5-O-H insertion and 1,2-H migra-
6) and a-tetrahydropyranyl derivatives (Entries 5 and 7). tion, when the thermal reaction of 18 was carried out in re-
For the thermal reaction of bicyclic ether 7, in the carbene fluxing toluene for 8 hours, 20 was isolated in 55% yield,
intermediate 8, migration of bond a would be expected to indicating that 1,5-O-H insertion of an alkylidenecarbene
afford 9 because migration of bond b is unlikely due to the is favored over 1,2-H migration. However, in competition
formation of the strained bridged bicyclic product 10. of 1,2-H migration with insertion of the alkyl carbene into
Thus, the thermal reaction of 7 in refluxing toluene for 7 the carbon-carbon bond, selective 1,2-H migration oc-
hours afforded 9 in 72% yield (Scheme 2).
curred. Thus, the thermal reaction of 21 under the same
Biographical Sketches
Sunggak Kim was born on at the Korea Advanced In- synthetic
methodologies
March 17, 1946 in Kyung- stitute of Science. He was utilizing carbenes, cations,
buk province, Korea. He promoted to Professor of and anions, his major re-
studied chemistry at Seoul Chemistry at Korea Ad- search emphasis in recent
National University, where vanced Institute of Science years has been on the devel-
he obtained his B.S. in 1969. and Technology (KAIST) in opment of new free radical-
After he had served in Kore- 1986 and he is currently the mediated methodologies.
an Army for two and half director of Center for Mo- He is the author of 170 pub-
years, he went to Canada in lecular Design and Synthe- lications and two books. His
1972 to receive his graduate sis (CMDS). His research major scientific awards in-
training at McGill Universi- interests focus on the design clude the Korean Chemical
ty in Montreal, where he and the development of new Society Award for Young
did his Ph.D degree with reactions and strategies with Chemists (1985), the Kore-
Professor George Just. He general utility in organic an Federation of Science
moved to Harvard in 1976, synthesis. He developed and Technology Societies
where he spent three years several synthetically useful Award (1991), and the Ko-
on postdoctoral studies with reagents including reduc- rea Science Prize in Chem-
Professor E. J. Corey. In ing, oxidizing, and coupling istry (1994).
1979, he returned to Korea reagents. Although he con-
to join the chemistry faculty tinues his interest in new
Joo-Yong Yoon was born gak Kim at the KAIST (Ko- sign and Synthesis, KAIST
in Seoul, Korea, in 1971. He rea Advanced Institute of as a postdoctoral fellow. At
graduated from the College Science and Technology) in present he is doing postdoc-
of Engineering of Hanyang 1999. From 1999 to 2000 he torate research in Prof. P. A.
University in 1994 and got has worked on non-stannane Wender’s laboratory at the
his Ph.D degree under the based radical chemistry at Stanford University.
guidance of Professor Sung- Center for Molecular De-
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

1624
S. Kim, J.-Y. Yoon
FEATURE ARTICLE
Table 1 Ring Expansion of a-Oxacyclo-N-aziridinylimines
Ph
Ph
Ph
O
[1,5-O-H]
Yield (%)b
59
Substratea
Entry
1
Time (h)
5
CH N A
18
Product
HO
O
(CH2)7CH3
(CH2)7CH3
CH N A
19
20: 55%
A = 2-phenyl-N-aziridinyl
O
O
11
Ph
Ph
N A
CH
[1,2-H]
O
2
8
5
5
58
69
60
O
O
CH
21
N
A
O
CH
O
22
H
12
Ph
CH2
Ph
CH N A
O
O
Me
3
23
24: 84%
O
Scheme 3
CH3
CH3
13
CH2Ph
CH2Ph
CH3
4
CH N Ac
H3C
O
H3C
O
CH3
n
n
n
14
O
O
O
R
O
O
R
O
cis/trans = 1/2
cis/trans = 1/2
R
CH N
A
R
R
26
O
27
CH N A
O
25a: n = 1
25b: n = 2
R = CH2CH2Ph
O
8
62
5
n
15
cis/trans = 1/8
H
cis/trans = 1/8
O
R
R = PhCH2
28a: n = 1 70%
28b: n = 2 54%
CH N A
O
O
Scheme 4
n
n
m
m
CH3
CH3
n = 1, m = 2
n = 2, m = 1
16: n = 1, m = 2
17: n = 2, m = 1
[2,3]-sigmatropic reorganization.24 In thermal reaction of
a-azacyclo-N-aziridinylimines, we were interested in
whether there were any differences in chemical reactivi-
ties between a-oxacyclo- and a-azacyclo-N-aziridi-
nylimines. The effect of the ring size was first examined.
The thermal reaction of a-azetidinyl-N-aziridinylimine
29a in refluxing toluene for 6 hours did not give dihydro-
pyrrole 32a but b-aminoacetylene compound 31a in 81%
6
7
91
85
5
5
a All substrates are mixture of syn- and anti- isomers.
b Isolated yield.
cA = 2-Phenyl-N-aziridinyl.
conditions furnished only dehydropyran 24 in 84% yield yield, indicating that the reaction proceeded through the
as a result of selective 1,2-H migration in the carbene 22 formation of alkylidenecarbene intermediate 30a and sub-
and the following isomerization of the double bond.
sequent 1,2-H migration as shown in Scheme 5.
As shown in Scheme 4, we also briefly studied the thermal
reaction of a-cyclic acetal substituted N- aziridinylimines
25, in which insertion into carbon-carbon bond can not
occur. The thermal reaction of 25a in refluxing toluene for
5 h afforded 28a in 70% yield, suggesting that the reaction
would proceed via oxonium ylide intermediate 27a. A
similar result was also obtained with 25b.
N
A
∆
+
N
X
N
X
NH
X
NH
X
29a:
X = CH2Ph
29b:X = tosyl
30
31a:
31b:
32
81%
78%
In the case of ammonium ylides,22 unlike sulfur ylides,
stable and isolable ammonium ylides have not been yet re-
ported in the literature. This difference in stability is prob-
ably due to the absence of pp-dp orbital interaction which
contributes to the stabilization of the charge on the sulfur
atom. However, ammonium ylides are reactive species
which readily undergo the Stevens rearrangement23 and
Scheme 5
Similarly, the thermolysis of 29b gave 31b in 78% yield.
It is interesting that 1,2-H migration is favored over am-
monium ylide formation or 1,5-N-H insertion with elec-
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

FEATURE ARTICLE
Carbene Reactions of a-Oxacyclo- and a-Azacyclo-N-aziridinylimines
1625
tron-rich azetidine 29a. This result is in sharp contrast atom would increase the formation of the ammonium
with the result obtained with compound 18, in which 1,5- ylide relative to 1,2-H migration by electrostatic interac-
O-H insertion was favored over 1,2-H migration. In order tion of an electron-deficient alkyl carbene with lone-pair
to examine the feasibility of the formation of the ammoni- electrons on the nitrogen atom. Thus, the electron densi-
um ylides, we began our studies with a-alkyl substituted- ties at various nitrogen atoms were calculated by
a-pyrrolidinyl-N-aziridinylimines 33 from which 1,2-H MOPAC25 using PM3 method26 as shown in the Figure.
migration could not take place. When pyrrolidine deriva- According to the computational data, the order of increas-
tive 33a was refluxed in toluene 6 hours, piperidinyl de- ing the electron density at the nitrogen atom is trifluoro-
rivative 36a was isolated in 70% yield. The possible acetyl, p-toluenesulfonyl, benzyloxycarbonyl, benzoyl,
rationale for this observation is outlined in Scheme 6.
and benzyl group. Since the trifluoroacetyl protected 41e
has the lowest electron density at the nitrogen atom, 46e
from 1,2-H migration would be formed the most. Similar-
ly, it is expected that the most 44a would be produced
with benzyl protected 41a.
∆
N
N
N
N
X
N
A
X
X
X
34
35
33a:
33b:
36a:
36b:
X = COPh
X = BOC
70%
59%
∆
N
A
N
X
N
N
Scheme 6
X
X
42
43
41a : X = CH2Ph
41c : X = Cbz
41b : X = COPh
41d : X = tosyl
The thermal reaction of 33a in refluxing toluene would
generate carbene intermediate 34 via aziridine ring open-
ing and subsequent loss of styrene and nitrogen gas. Car-
bene 34 would be captured by a nitrogen atom to produce
the transient ammonium ylide 35 from which 36a is ob-
tained via rearrangement. Furthermore, this ring expan-
sion reaction could be similarly applied to the lactam
derivatives (Scheme 7). Thermal reaction of 37a in reflux-
ing toluene for 5 hours afforded 40a in 81% yield via am-
monium ylide intermediate 39. A similar result was also
obtained with 37b.
41e : X = COCF3
N
N
N
X
X
X
44
46
45
∆
+
N
N
N
A
N
X
X
X
47a : X = CH2Ph
47c : X = Cbz
47e : X = COCF3
48
49
47b : X = COPh
47d : X = tosyl
Scheme 8
O
O
O
H
NH
NH
N
∆
N
A
O
O
CH3
CH3
CH3
n
n
n
PhCH2
N
Ph C N
PhCH2 O C N
Ph
Ph
Ph
CH3
5.4820
CH3
5.0951
CH3
5.0743
37a: n=1
37b: n=2
38
39
O
O
S N
O
O
NH
CH3
CH3
CH3
n = 1
81%
62%
40a:
40b:
CH3
CF3 C N
CH3
n = 2
n
5.0667
5.0193
Ph
Figure Electron density of various nitrogen atoms.
Scheme 7
Some experimental results for the thermal reaction of 41
and 47 are summarized in Table 2. Among piperidine de-
rivatives 44, N-benzyl protected derivative 44a was labile
and was reduced into N-benzylpiperidine with sodium cy-
anoborohydride and zinc chloride in methanol.27 Similar-
ly, 48a and 49a were also unstable and were reduced into
N-benzylazepane and N-benzyl-2-methylpiperidine, re-
spectively (Scheme 9). The experimental results obtained
with pyrrolidine derivative 41 are in good agreement with
the computational data. The thermal reaction of 41b in re-
fluxing toluene for 2 h afforded the ring expanded product
44b in 59% yield along with 1,2-H migration product 46b
To study the relative ease of 1,2-H migration and ring ex-
pansion via ammonium ylide intermediates in carbenes,
we examined the thermal reaction of a-pyrrolidinyl-N-
aziridinylimine 41 (Scheme 8). We anticipated that the re-
action would give a mixture of two products 44 and 45 re-
sulting from 1,2-H migration and ring expansion via an
ammonium ylide intermediate 43 and the ratio of 44 and
45 would depend very much on the electron density at the
nitrogen atom, suggesting that the ratio would be con-
trolled by introducing different substituents. According to
our reasoning, the higher electron density at the nitrogen
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

1626
S. Kim, J.-Y. Yoon
FEATURE ARTICLE
in 12% yield. When slightly more electron-poor carbam- intermediates for oxetane derivatives and (ii) insertion of
ate 41c was used, a 50:26 mixture of 44c and 46c was ob- alkyl carbenes into carbon-carbon bonds for tetrahydro-
tained as we anticipated. As shown in Table 2, it is furan and tetrahydropyran derivatives. Similarly, thermal
gratifying that the reaction of 41a in refluxing toluene reaction of a-azetidinyl-N-aziridinylimines proceeded via
gave 44a exclusively, whereas 1,2-H migration product alkylidene carbene intermediates. However, the thermal
46e was a sole product with 41e under the same condition. reaction of a-pyrrolidinyl- and a-piperidinyl-N-aziridi-
However, as compared with pyrrolidine derivatives 41, nylimines proceeded via the formation of ammonium
piperidine derivatives 47 gave much lower selectivities. ylides and/or 1,2-H migration and the ratio of two pro-
Somewhat surprisingly, the thermal reaction of 47 in re- cesses would depend on the electron density of the nitro-
fluxing toluene provided 1,2-H migration products con- gen atom and the ring size.
sistently as a major product. For instance, the reaction of
47a under the same conditions afforded 1,2-H migration
product 49a as a major product along with the ring expan-
All reagents used were of commercial quality. All dry solvents were
freshly distilled under N2 from the appropriate drying agent before
sion product 48a in 19% yield. This result is in sharp con-
trast with the result obtained with 41a, where the ring
expansion product was obtained as a sole product. Simi-
larly, 1,2-H migration products 49b and 49c were ob-
tained as major products with 47b and 47c. In the case of
47e, only 1,2-H migration product 49e was obtained. Al-
though we have no clear answer for this observation, the
results may be due to higher strain energy of pyrrolidine
derivatives 41 relative to piperidine derivatives 47, there-
by promoting the ring expansion of 41.28 Spectral data of
compounds 44, 46, 48 and 49 are assembled in Table 3.
use. 1H NMR and 13C NMR spectra were recorded on Bruker AC-
200 and AC-300 spectrometers. The chemical shifts in CDCl3 or
benzene-d6 reported in d (ppm) relative to CDCl3 or Me4Si as an in-
ternal reference. IR spectra were measured on a Bomen MB-100
Fourier Transform spectrometer. HRMS were obtained on a VG
Autospec Ultma GC/MS system using direct insertion probe (DIP)
and electron impact (EI) (70 eV) method. Flash chromatography
was carried out on Merck silica 60, 230-400 mesh ASTM; eluents
are given in parentheses. Analytical TLC was performed on E.
Merck precoated silica gel 60 F254 plates.
Thermal Reaction of a-Oxetanyl-N-aziridinylimine 1a; 4-Phen-
ethyl-2,3-dihydrofuran (6a); Typical Procedure
In a flask equipped with a reflux condenser, a-oxetanyl-N-aziridi-
nylimine 1a (120 mg, 0.39 mmol) was dissolved in degassed tolu-
ene (3 mL) under N2. The reaction flask was immersed into a
preheated oil bath which was maintained at 120 °C. The reaction
mixture was heated at reflux for 5 h and the evolution of N2 gas ob-
served. The mixture was allowed to cool to r.t. and concentrated to
dryness under reduced pressure. The residue was purified by col-
umn chromatography on silica gel (eluent: hexane/EtOAc, 30:1) to
afford the dihydrofuran derivative 6a (40 mg) in 59% yield.
NaBH3CN
N
N
ZnCl2
CH2Ph
CH2Ph
50
44a
NaBH3CN
ZnCl2
+
+
N
N
N
N
CH2Ph
1H NMR (200 MHz, CDCl3): d = 2.36 (t, 2 H, J = 8.0 Hz), 2.54 (t,
2 H, J = 9.4 Hz), 2.74 (t, 2 H, J = 8.0 Hz), 4.29 (t, 2 H, J = 9.4 Hz),
6.06 (s, 1 H), 7.16-7.27 (m, 5 H).
CH2Ph
CH2Ph
CH2Ph
52
51
49a
48a
13C NMR (50 MHz, CDCl3): d = 28.2, 32.4, 34.6, 69.7, 113.9,
125.8, 128.3, 140.0, 141.9.
Scheme 9
IR (film): n = 2905, 1663, 1496, 1452 cm-1.
HRMS (EI): m/z calcd for C12H14O (M+): 174.1045, found
Table 2 Thermal Reaction of 41 and 47
174.1040.
product
yield
product
yield
3,4-Dihydro-6-phenethyl-2H-pyran (5b)
substrate
substrate
1H NMR (200 MHz, CDCl3): d = 1.62-1.70 (m, 2 H), 1.80-1.85
(m, 2 H), 2.13 (t, 2 H, J = 7.8 Hz), 2.64 (t, 2 H, J = 7.8 Hz), 3.84 (t,
2 H, J = 5.1 Hz), 4.25 (t, 1 H, J = 3.6 Hz), 6.97-7.08 (m, 5 H).
44
46
48
49
41a
41b
41c
41d
41e
71%
59%
50%
17%
0%
0%
12%
26%
47%
60%
47a
47b
47c
47d
47e
19%
6%
3%
3%
0%
54%
64%
86%
81%
72%
13C NMR (50 MHz, CDCl3): d = 20.6, 22.9, 33.8, 36.8, 65.9, 95.5,
125.9, 128.4, 128.6, 142.0, 154.0.
IR (film): n = 2933, 1675 cm-1.
HRMS (EI): m/z calcd for C13H16O (M+): 188.1201, found
188.1208.
3-Phenethylcyclohept-2-ene Ether (5c)
1H NMR (200 MHz, CDCl3): d = 1.45-1.70 (m, 4 H), 1.81-1.95
(m, 2 H), 2.11 (t, 2 H, J = 7.8 Hz), 2.60 (t, 2 H, J = 7.8 Hz), 3.76 (t,
2 H, J = 5.1 Hz), 4.44 (t, 1 H, J = 5.6 Hz), 6.94-7.09 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 20.6, 23.9, 25.0, 31.6, 32.9, 64.9,
92.5, 126.5, 127.7, 128.4, 139.8, 153.8.
In conclusion, it has been found that carbene reactions of
a-heterocyclo-N-aziridinylimines depend very much on
the nature of heteroatoms and ring sizes. Ring expansion
of a-oxacyclo-N-aziridinylimines occurred via two differ-
ent pathways (i) 1,5-O-H insertion of alkylidenecarbene
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

FEATURE ARTICLE
Carbene Reactions of a-Oxacyclo- and a-Azacyclo-N-aziridinylimines
1627
Table 3 Spectral Data of Compounds 44, 46, 48, and 49 (Scheme 8)
Product
1H NMR (200 MHz, CDCl3 /TMS) d, J (Hz)
13C NMR (50 MHz, CDCl3/
TMS) d, J (Hz)
IR (film)
HRMS
Calcd
Found
n (cm−1)
44b
1.77-1.92 (m, 2 H), 2.37-2.58 (m, 2 H),
3.86 (t, 2 H, J = 8.1), 5.01 (2 s, 1 H), 6.72
(br s, 1 H), 7.24-7.46 (m, 5 H)
23.1, 30.1, 41.5, 104.5, 126.8,
128.6, 131.4, 134.4, 134.8,
160.2
2924, 1637,
1388, 1263,
1148
187.0997
187.0997
217.1103
187.0995
187.0993
217.1109
46b
44c
2.15 (s, 3 H), 2.59 (t, 2 H, J = 6.5), 3.45 (q,
2 H, J = 6.5), 5.04 (m, 1 H), 7.24-7.78 (m,
5 H)
23.1, 30.1, 41.5, 104.5, 126.8,
128.6, 131.4, 134.4, 134.8,
160.2
2930, 1656,
1447, 1270,
1176
1.69-1.87 (m, 2 H), 1.97-2.06 (m, 2 H),
3.58 (t, 2 H, J = 6.1), 4.83 (m, 1 H), 5.07
(2 s, 2 H), 6.79 (d, 1 H, J = 8.5), 7.23-7.36
(m, 5 H)
21.9, 29.5, 41.0, 66.4, 108.5,
127.8, 127.9, 128.5, 130.7,
137.1, 151.2
2933, 1701,
1399, 1247,
1192
46c
44d
46d
2.11 (s, 3 H), 3.18 (q, 2 H, J = 6.7), 3.84
(t, 2 H, J = 9.2), 4.95 (m, 1 H), 5.12 (2 s,
2 H), 7.24-7.35 (m, 5 H)
18.9, 27.5, 40.9, 66.4, 113.9,
127.8, 127.9, 128.5, 137.0,
138.3, 153.4
2888, 1663,
1454, 1272,
1132
217.1103
237.0823
237.0823
217.1105
237.0819
237.0815
1.55-1.74 (m, 2 H), 1.84-1.90 (m, 2 H),
2.40 (s, 3 H), 3.31-3.37 (m, 2 H), 4.95
(m, 1 H), 6.61 (d, 1 H, J = 8.4), 7.28 (d, 2 H,
J = 8.3), 7.68 (d, 2 H, J = 8.3)
21.6, 22.8, 30.7, 46.9, 123.5,
126.7, 127.1, 129.2, 137.2,
144.8
2945, 1644,
1450, 1339,
1162
2.11 (s, 3 H), 2.40 (s, 3 H), 2.50 (t, 2 H, J =
6.6), 2.92 (t, 2 H, J = 6.6), 4.54 (t, 1 H, J =
6.1), 7.28 (d, 2 H, J = 8.3), 7.68 (d, 2 H, J =
8.3)
18.7, 21.6, 27.8, 46.4, 126.9,
127.5, 129.0, 129.1, 137.8,
144.8
2865, 1638,
1595, 1498,
1301, 1094
46e
48b
48c
2.12 (s, 3 H), 2.42-2.47 (m, 2 H), 2.98-
17.0, 27.5, 44.5, 113.9, 114.2 (q,
J = 342.6), 128.9, 154.3 (q, J =
37.9)
2938, 1741,
1498, 1268,
1028
179.0558
201.1154
231.1259
179.0558
201.1142
231.1247
3.27 (m, 2 H), 4.72 (m, 1 H)
1.68-1.84 (m, 4 H), 2.00-2.11 (m, 2 H),
3.61 (t, 2 H, J = 5.2), 5.02 (t, 1 H, J = 5.0),
6.23 (s, 1 H), 7.23-7.51 (m, 5 H)
24.3, 24.8, 28.0, 43.2, 109.0,
127.1, 127.5, 129.0, 130.6,
133.4, 169.1
2944, 1631,
1378, 1273,
1149
1.64-1.81 (m, 4 H), 1.97- 2.06 (m, 2 H),
3.69 (t, 2 H, J = 5.9), 5.14 (s, 2 H), 5.17
(t, 1 H, J = 4.8), 6.18 (s, 1 H), 7.28-7.35 (m,
5 H)
23.9, 25.3, 29.2, 40.7, 66.4,
109.0, 127.8, 127.9, 128.5,
131.2, 137.1, 151.1
2841,1661,
1498,1136,
1028
49c
48d
1.59-1.75 (m, 4 H), 2.18 (t, 2 H, J = 5.5),
3.57 (m, 2 H), 4.89 (d, 2 H, J = 3.5), 5.15 (s,
2 H), 7.28-7.32 (m, 5 H)
22.7, 25.7, 32.6, 44.6, 66.9,
111.5, 127.5, 127.9, 128.5,
138.5, 143.9, 154.3
2931, 1705,
1397, 1340,
1250, 1190
231.1259
251.0980
231.1239
251.0975
1.42-1.53 (m, 4 H), 1.73-1.85 (m, 2 H),
2.32 (s, 3 H), 3.41 (t, 2 H, J = 5.0), 4.97 (m,
1 H), 6.38 (d, 1 H, J = 2.3), 7.18 (d, 2 H, J =
8.4), 7.62 (d, 2 H, J = 8.3)
21.4, 23.1, 27.6, 29.7, 48.4,
120.9, 126.2, 128.0, 132.3,
140.2, 143.9
2863, 1598,
1495, 1402,
1250, 1032
49d
49e
1.40-1.58 (m, 4 H), 1.92 (t, 2 H, J = 5.5),
2.35 (s, 3 H), 3.55 (t, 2 H, J = 5.0), 4.72 (s,
1 H), 4.96 (s, 1 H), 7.22 (d, 2 H, J = 8.3),
7.66 (d, 2 H, J = 8.2)
21.3, 24.1, 24.6, 31.7, 47.7,
108.0, 126.7, 127.1, 129.4,
137.8, 142.9
2942, 1645,
1447, 1340,
1159, 1092
251.0980
193.0714
251.0972
193.0717
1.63-1.87 (m, 4 H), 2.27 (t, 2 H, J = 5.2),
3.68 (t, 2 H, J = 5.4), 4.58 (d, 2 H, J = 3.2)
24.2, 25.7, 30.7, 46.5, 98.5,
114.2 (q, J = 338.4), 17.0, 27.5,
44.5, 113.9, 114.2 (q, J = 338.3),
137.7, 154.3 (q, J = 37.4)
2948, 1738,
1455, 1272,
1014
6-Benzyl-2,3,3a,4,5,6-hexahydrobenzofuran (9) (Scheme 2)
1H NMR (200 MHz, CDCl3): d = 1.60-1.67 (m, 6 H), 1.92-1.98
(m, 1 H), 2.31-2.37 (m, 1 H), 2.55 (d, 2 H, J = 7.5 Hz), 3.96 (t, 2 H,
J = 5.0 Hz), 4.52 (d, 1 H, J = 3.8 Hz), 7.08-7.21 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 22.3, 28.0, 30.6, 34.9, 39.9, 49.3,
66.2, 95.3, 126.3, 127.8, 128.1, 138.2, 160.2.
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

1628
S. Kim, J.-Y. Yoon
FEATURE ARTICLE
IR (film): n = 2921, 1653, 1440, 1264, 1003 cm-1.
HRMS (EI): m/z calcd for C15H18O (M+): 214.1358, found
13C NMR (50 MHz, CDCl3): d = 24.6, 31.5, 36.4, 41.2, 43.2, 67.7,
99.0, 124.1, 126.0, 129.7, 130.0, 134.6, 137.3, 166.1.
214.1347.
IR (film): n = 1670, 1154, 1098, 1013, 754 cm-1.
4-Heptyl-2,3-dihydrofuran (11) (Table 1)
HRMS (EI): m/z calcd for C14H16O (M+): 200.1201, found
200.1217.
1H NMR (200 MHz, CDCl3): d = 0.86 (t, 3 H, J = 6.7 Hz), 1.23-
1.44 (m, 10 H), 2.01 (t, 2 H, J = 6.8 Hz), 2.50 (tt, 2 H, J = 9.3, 1.0
Hz), 4.27 (t, 2 H, J = 9.3 Hz), 6.03 (t, 1 H, J = 1.0 Hz).
4a-Methyl-3,4,4a,5-tetrahydro-2H-benzo[g]chromene (17) (Ta-
ble 1)
13C NMR (50 MHz, CDCl3): d = 14.1, 22.7, 26.2, 28.0, 29.3, 29.6,
31.9, 32.4, 69.7, 114.8, 139.4.
IR (film): n = 2926, 2855, 1462, 1094 cm-1.
HRMS (EI): m/z calcd for C11H20O (M+): 168.1514, found
1H NMR (200 MHz, CDCl3): d = 1.09 (s, 3 H), 1.60-1.73 (m, 2 H),
1.79-1.86 (m, 1 H), 2.03-2.19 (m, 1 H), 2.59 (d, 1 H, J = 15.2 Hz),
2.88 (d, 1 H, J = 15.2 Hz), 3.72 (dt, 1 H, J = 2.3, 8.5 Hz), 4.19-4.28
(m, 1 H), 5.84 (s, 1 H), 6.96-7.16 (m, 4 H).
13C NMR (50 MHz, CDCl3): d = 21.9, 22.3, 34.9, 36.5, 45.3, 68.9,
104.6, 124.6, 124.8, 126.3, 127.3, 131.6, 134.8, 161.5.
168.1518.
4,5,6,7,8,8a-Hexahydro-1H-cyclohepta[c]furan (12) (Table 1)
1H NMR (200 MHz, CDCl3): d = 1.23-1.63 (m, 8 H), 2.00-2.36
(m, 2 H), 2.71-2.80 (m, 1 H), 3.59 (t, 1 H, J = 8.5 Hz), 4.15 (t, 1 H,
J = 8.5 Hz), 5.83 (t, 1 H, J = 1.6 Hz).
IR (film): n = 1642, 1277, 1142, 1103, 753 cm-1.
HRMS (EI): m/z calcd for C14H16O (M+): 200.1201, found
200.1216.
13C NMR (50 MHz, CDCl3): d = 25.4, 28.2, 28.8, 30.4, 34.8, 45.5,
3-Phenyl-2,3-dihydrofuran (20) (Scheme 3)
76.5, 118.7, 140.9.
1H NMR (200 MHz, CDCl3): d = 3.71 (dd, 1 H, J = 2.3, 3.6 Hz),
3.75-3.92 (m, 1 H), 4.10 (dd, 1 H, J = 2.3, 3.6 Hz), 5.52 (t, 1 H,
J = 5.2 Hz), 6.08 (d, 1 H, J = 5.2 Hz), 7.11-7.29 (m, 5 H).
IR (film): n = 2955, 2918, 1472, 1079 cm-1.
HRMS (EI): m/z calcd for C9H14O (M+): 138.1045, found 138.1051.
13C NMR (50 MHz, CDCl3): d = 44.8, 73.6, 79.7, 126.1, 128.4,
128.5, 138.9, 165.2.
IR (film): n = 2918, 1652, 1475, 1455 cm-1.
HRMS (EI): m/z calcd for C10H10O (M+): 146.0732, found
3a-Methyl-3,3a,4,5-tetrahydronaphtho[1,2-c]furan (13) (Table
1)
1H NMR (200 MHz, CDCl3): d = 1.21 (s, 3 H), 1.65-1.98 (m, 2 H),
2.78-3.11 (m, 2 H), 3.98 (d, 1 H, J = 8.4 Hz), 4.33 (d, 1 H, J = 8.4
Hz), 6.73 (s, 1 H), 7.07-7.38 (m, 4 H).
146.0737.
13C NMR (50 MHz, CDCl3): d = 22.4, 26.5, 33.2, 42.9, 84.1, 121.1,
5-Phenethyl-6-methyl-3,4-dihydro-2H-pyran (24) (Scheme 3)
1H NMR (200 MHz, CDCl3): d = 1.63-1.73 (m, 4 H), 1.70 (s, 3 H),
3.15 (s, 2 H), 3.16 (t, 2 H, J = 5.1 Hz), 6.96-7.13 (m, 5 H).
13C NMR (50 MHz, 7 wt % benzene-d6 in CCl4): d = 17.0, 23.5,
24.7, 38.8, 65.4, 104.7, 126.0, 128.4, 128.5, 141.0, 172.0.
123.9, 125.6, 126.0, 129.0, 129.1, 133.3, 138.4.
IR (film): n = 2923, 1691, 1483, 1453, 1147, 1087 cm-1.
HRMS (EI): m/z calcd for C13H14O (M+): 186.1045, found
186.1046.
5-Phenethyl-2,3-dihydro-[1,4]dioxine (28a) (Scheme 4)
1H NMR (200 MHz, CDCl3): d = 2.24 (dd, 2 H, J = 6.1, 8.2 Hz),
2.77 (t, 2 H, J = 7.3 Hz), 3.94-3.98 (m, 2 H), 4.06-4.11 (m, 2 H),
5.76 (s, 1 H), 7.16-7.32 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 32.5, 33.5, 63.8, 64.6, 122.2,
125.8, 128.2, 128.4, 136.6, 141.5.
4-Benzyl-2,6-dimethyl-3,4-dihydro-2H-pyran (14) (Table 1)
1H NMR (200 MHz, 7 wt % benzene-d6 in CCl4): d = 1.12 (d, 3 H,
J = 6.3 Hz), 1.32, 1.36 (2 s, 3 H), 1.38-1.50 (m, 2 H), 1.71-1.80
(dd, 1 H, J = 6.9, 12.3 Hz), 2.40-2.52 (m, 1 H), 2.75 (dd, 1 H,
J = 5.0, 13.8 Hz), 3.90-4.16 (m, 1 H), 4.46 (m, 1 H), 6.98-7.18 (m,
5 H).
13C NMR (50 MHz, 7 wt % benzene-d6 in CCl4): d = 12.2, 21.4,
IR (film): n = 1684, 1174, 1130, 1093, 701 cm-1.
HRMS (EI): calcd for C12H14O2 (M+): 190.0994, found 190.1005.
38.1, 39.2, 41.5, 74.8, 89.7, 126.5, 128.8, 129.4, 140.3, 159.4.
IR (film): n = 2970, 1693, 1495, 1451, 1168 cm-1.
HRMS (EI): m/z calcd for C14H18O (M+): 202.1358, found
2-Benzyl-6,7-dihydro-5H-[1,4]dioxepine (28b) (Scheme 4)
1H NMR (200 MHz, CDCl3): d = 2.01 (m, 2 H), 2.18 (t, 2 H, J = 8.2
Hz), 2.74 (t, 2 H, J = 7.2 Hz), 3.96 (t, 2 H, J = 5.7 Hz), 4.06 (t, 2 H,
J = 5.7 Hz), 5.66 (s, 1 H), 7.13-7.26 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 29.4, 32.0, 40.3, 60.6, 69.7, 75.9,
126.3, 128.3, 128.6, 140.7, 208.1.
IR (film): n = 1680, 1188, 1079 cm-1.
HRMS (EI): m/z calcd for C13H16O2 (M+): 204.1150, found
202.1340.
8-Benzyl-2,3,4,4a,5,6,7,8-octahydrocyclohepta[b]pyran (15)
(Table 1)
1H NMR (200 MHz, CDCl3): d = 1.25-1.34 (m, 8 H), 1.62-1.68
(m, 2 H), 2.10-2.22 (m, 1 H), 2.39-2.43 (m, 1 H), 2.52 (d, 2 H,
J = 7.1 Hz), 3.96 (t, 2 H, J = 5.2 Hz), 4.35 (d, 1 H, J = 5.4 Hz),
7.05-7.25 (m, 5 H).
204.1157.
13C NMR (50 MHz, CDCl3): d = 20.9, 22.9, 24.6, 25.2, 33.1, 34.6,
38.9, 45.5, 65.4, 98.2, 126.3, 127.5, 128.1, 138.0, 159.2.
IR (film): n = 2977, 1682, 1451, 1092, 1059 cm-1.
Thermal Reaction of a-Azetidino-N-aziridinylimine 29a; N-
Benzylbut-3-ynylamine (31a); Typical Procedure
HRMS (EI): m/z calcd for C17H22O (M+): 242.1671, found
242.1690.
In a flask equipped with a reflux condenser, a-azetidinyl-N-aziridi-
nylimine 29a (63 mg, 0.22 mmol) was dissolved in degassed tolu-
ene (2 mL) under N2. After stirring at 120 °C for 6 h, TLC showed
the disappearance of the starting material and the generation of a
new spot. The mixture was cooled to r.t. and concentrated to dryness
under reduced pressure. The residue was purified by column chro-
matography on silica gel (eluent: hexane/EtOAc, 2:1) to afford 31a
(28 mg, 81%).
10a-Methyl-2,9,10,10a-tetrahydro-1H-3-oxabenzo[f]azulene
(16) (Table 1)
1H NMR (200 MHz, CDCl3): d = 1.21 (s, 3 H), 1.86-2.08 (m, 4 H),
2.89-3.06 (m, 2 H), 4.18-4.26 (m, 2 H), 5.80 (s, 1 H), 7.01-7.16
(m, 4 H).
Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York

FEATURE ARTICLE
Carbene Reactions of a-Oxacyclo- and a-Azacyclo-N-aziridinylimines
1629
1H NMR (300 MHz, CDCl3): d = 1.69 (br s, 1 H), 1.98 (t, 1 H,
J = 2.6 Hz), 2.40 (td, 2 H, J = 6.6, 2.6 Hz), 2.79 (t, 2 H, J = 6.6 Hz),
3.80 (s, 2 H), 7.18-7.32 (m, 5 H).
13C NMR (75 MHz, CDCl3): d = 19.5, 47.3, 53.4, 69.5, 82.5, 127.0,
128.1, 128.4, 140.1.
IR (film): n = 3296, 2922, 1456, 1121 cm-1.
HRMS (EI): m/z calcd for C11H13N (M+): 159.1048, found
1-Benzylpiperidine (50); Typical Procedure
A solution of 41a (90 mg, 0.25 mmol) was stirred in refluxing tolu-
ene for 4 h and the mixture was concentrated under reduced pres-
sure. After MeOH (3 mL) was added to the crude product,
NaBH3CN (39 mg, 0.50 mmol) and ZnCl2 (42 mg, 0.25 mmol) were
added. After stirring for 1 h at r.t., most of the MeOH was evaporat-
ed under reduced pressure and the mixture was poured into aq 0.1
N NaOH solution (10 mL). The aqueous layer was extracted with
EtOAc (20 mL) and the organic layer was washed with brine (20
mL). The combined organic extracts were dried, filtered, and con-
centrated under reduced pressure. The crude product was purified
by silica gel column chromatography (eluent: hexane/EtOAc, 2:1)
to afford 50 (31 mg, 71%) as a colorless oil.
159.1065.
(N-But-3-ynyl)-4-methylbenzenesulfonamide (31b) (Scheme 6)
1H NMR (300 MHz, CDCl3): d = 1.97 (t, 1 H, J = 2.6 Hz), 2.32 (tt,
2 H, J = 6.6, 2.6 Hz), 2.41 (s, 3 H), 3.08 (td, 2 H, J = 6.6, 6.3 Hz),
4.87 (t, 1 H, J = 6.3 Hz), 7.29 (d, 2 H, J = 8.0 Hz), 7.73 (d, 2 H,
J = 8.4 Hz).
13C NMR (50 MHz, CDCl3): d = 19.7, 21.5, 41.2, 70.8, 80.3, 127.0,
129.8, 136.9, 143.6.
1H NMR (200 MHz, CDCl3): d = 1.38-1.47 (m, 2 H), 1.57 (m, 4 H,
J = 5.9 Hz), 2.28 (t, 4 H, J = 4.7 Hz), 3.49 (s, 2 H), 7.22-7.31 (m, 5
H).
13C NMR (50 MHz, CDCl3): d = 24.3, 25.9, 54.4, 63.8, 126.7,
128.0, 129.1, 138.5.
IR (film): n = 3028, 2935, 2765, 1454, 1347, 1114 cm-1.
HRMS (EI): m/z calcd for C12H17N (M+): 175.1361, found
IR (film): n = 3289, 2922, 1599, 1427, 1326, 1160, 1094 cm-1.
HRMS (EI): m/z calcd for C11H13NO2S (M+): 223.0667, found
223.0669.
(6-Methyl-3,4-dihydro-2H-pyridin-1-yl)phenylmethanone
(36a) (Scheme 6)
175.1377.
1H NMR (200 MHz, CDCl3): d = 1.56, 1.62 (2 s, 3 H), 1.90-2.06
(m, 4 H), 3.46, 3.76 (2 t, 2 H, J = 5.9 Hz), 6.21, 7.10 (2 s, 1 H),
7.33-7.47 (m, 5 H).
1-Benzylazepane (51) (Scheme 9)
1H NMR (200 MHz, CDCl3): d = 1.25-1.39 (m, 4 H), 1.40-1.51
(m, 2 H), 1.58-1.64 (m, 2 H), 2.39 (t, 4 H, J = 4.7 Hz), 3.83 (s, 2
H), 7.24-7.38 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 21.7, 27.4, 40.6, 46.1, 116.4,
122.2, 127.4, 128.2, 128.3, 135.4, 168.7.
IR (film): n = 2927, 1637, 1387, 1269, 1149 cm-1.
HRMS (EI): m/z calcd for C13H15NO (M+): 201.1154, found
13C NMR (50 MHz, CDCl3): d = 22.1, 24.2, 53.7, 63.8, 125.9,
127.0, 127.7, 138.5.
IR (film): n = 3011, 2952, 1603, 1451, 1059 cm-1.
HRMS (EI): m/z calcd for C13H19N (M+): 189.1517, found
201.1154.
189.1523.
6-Methyl-3,4-dihydro-2H-pyridine-1-carboxylicAcidtert-Butyl
Ester (36b) (Scheme 6)
1-Benzyl-2-methylpiperidine (52) (Scheme 9)
1H NMR (200 MHz, CDCl3): d = 1.09 (d, 3 H, J = 6.3 Hz), 1.42-
1.58 (m, 2 H), 1.60-1.67 (m, 4 H), 2.37 (t, 2 H, J = 4.5 Hz), 2.40-
2.52 (m, 1 H), 3.49 (s, 2 H), 7.24-7.38 (m, 5 H).
1H NMR (200 MHz, CDCl3): d = 1.46 (s, 9 H), 1.64 (s, 3 H), 1.68-
1.83 (m, 2 H), 1.92 (t, 2 H, J = 5.9 Hz), 3.43-3.54 (m, 2 H), 6.47,
6.62 (2 s, 1 H).
13C NMR (50 MHz, CDCl3): d = 22.3, 24.3, 25.9, 34.6, 54.4, 57.3,
63.7, 126.7, 128.1, 128.7, 142.1.
13C NMR (50 MHz, CDCl3): d = 20.9, 26.9, 28.3, 40.9, 44.5, 64.3,
111.2, 120.3, 153.2.
IR (film): n = 3030, 2955, 1609, 1454, 1067 cm-1.
HRMS (EI): m/z calcd for C13H19N (M+): 189.1517, found
IR (film): n = 1697, 1397, 1360, 1165 cm-1.
HRMS (EI): m/z calcd for C11H19NO2 (M+): 197.1416, found
189.1527.
197.1419.
6-Benzyl-1,3,4,5-tetrahydro-2H-azepin-2-one (40a) (Scheme 7)
1H NMR (200 MHz, CDCl3): d = 1.76-1.89 (m, 2 H), 2.40-2.58
(m, 4 H), 3.34 (d, 2 H, J = 7.8 Hz), 4.94 (tt, 1 H, J = 7.8, 1.4 Hz),
7.13-7.31 (m, 5 H), 8.37 (br s, 1 H).
13C NMR (50 MHz, CDCl3): d = 19.5, 23.0, 32.0, 32.3, 105.2,
126.0, 128.1, 128.4, 134.8, 140.8, 170.8.
Acknowledgement
This work was supported by the Center for Molecular Design and
Synthesis (CMDS) and BK21 Project.
IR (film): n = 3203, 2946, 1671, 1392, 1183 cm-1.
References
HRMS (EI): m/z calcd for C13H15 NO (M+): 201.1154, found
201.1156.
(1) Kirmse, W. Carbene Chemistry, 2nd ed.; Academic Press:
New York, 1971.
(2) For reviews, see:
7-Benzyl-3,4,5,6-tetrahydroazocin-2(1H)-one (40b) (Scheme 7)
1H NMR (200 MHz, CDCl3): d = 1.69-1.78 (m, 2 H), 1.89-2.02
(m, 1 H), 2.10-2.19 (m, 1 H), 2.33 (t, 2 H, J = 8.0 Hz), 2.77 (t, 2 H,
J = 7.4 Hz), 3.33 (d, 2 H, J = 7.4 Hz), 5.14 (t, 1 H, J = 7.4 Hz), 6.93
(br s, 1 H), 7.12-7.32 (m, 5 H).
13C NMR (50 MHz, CDCl3): d = 22.4, 26.3, 32.6, 34.8, 36.1, 113.0,
126.2, 128.3, 128.5, 135.1, 139.6, 175.7.
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Synthesis 2000, No. 11, 1622–1630 ISSN 0039-7881 © Thieme Stuttgart · New York