Rhodium(II)-Catalyzed Annulation of Azavinyl Carbenes Through Ring-Expansion of 1,3,5-Trioxane: Rapid Access to Nine-Membered 1,3,5,7-Trioxazonines

Article abstract of DOI:10.1002/asia.201500493

The rhodium(II)-catalyzed denitrogenative coupling of N-alkylsulfonyl 1,2,3-triazoles with 1,3,5-trioxane led to nine-membered-ringed trioxazonines in moderate-to-good yields. 1,3,5-Trioxane, acting as an oxygen nucleophile, reacted with the α-aza-vinylca

Full text of DOI:10.1002/asia.201500493

DOI: 10.1002/asia.201500493
Full Paper
Rhodium Catalysis
Rhodium(II)-Catalyzed Annulation of Azavinyl Carbenes Through
Ring-Expansion of 1,3,5-Trioxane: Rapid Access to Nine-
Membered 1,3,5,7-Trioxazonines
[a]
[a, b]
[a]
[a]
Jola Pospech, Raffaella Ferraccioli,
Helfried Neumann, and Matthias Beller*
Abstract: The rhodium(II)-catalyzed denitrogenative cou-
pling of N-alkylsulfonyl 1,2,3-triazoles with 1,3,5-trioxane led
to nine-membered-ringed trioxazonines in moderate-to-
good yields. 1,3,5-Trioxane, acting as an oxygen nucleophile,
reacted with the a-aza-vinylcarbene intermediate, giving rise
to ylide formation, which was probably the key step in the
reaction. Triazoles that contained aryl substituents with vari-
ous electronic and steric features on the C4 carbon atom
were well-tolerated. The synthesis of trioxazonine derivatives
was achieved through a one-pot, two-step procedure from
I
1-mesylazide and a terminal alkyne by combining Cu-cata-
lyzed 1,3-dipolar cycloaddition and rhodium-catalyzed trans-
formations.
Introduction
The reason for this lack of use of 1,3,5-trioxane may be the
lack of synthetic methods that are capable of its efficient use.
Only a few examples have been reported in the literature and
1
,3,5-Trioxane (1) is a safe, stable solid that is used in synthetic
3
organic chemistry essentially as a clean and anhydrous source
these examples involve the installation of s-trioxane onto sp
[
1]
2
[3,4]
of formaldehyde (Figure 1). It is surprising that, so far, com-
pound 1 has not been used to build-up or decorate molecules
of potential pharmaceutical interest, although related structur-
ally motifs are present in molecules that have long been
known to be antidepressant and antimalarial agents, such as
or sp carbon atoms through radical transformations.
The discovery of methods that allow the connection of such
readily available building blocks, which are otherwise hardly
utilizable, with high chemo-, regio-, and stereoselectivity is of
fundamental and practical interest.
[
2]
paraldehyde and artemisinin.
Catalytic methods that utilize di-rhodiumÀcarbene species
constitute a versatile synthetic tool, in particular for CH-func-
tionalization reactions. In addition, readily generated electro-
philic metalÀcarbenes show high reactivities towards cyclopro-
panation reactions, XÀH (X=O, S, N) bond insertions, 1,2-shifts,
[
5]
dipolar cycloaddition reactions, and ylide formations. Hence,
in recent years, the number of applications of these methods
has increased parallel to the development of improved syn-
thetic procedures for the preparation of the corresponding
[
6]
diazo-based precursors. For instance, specific donor/acceptor
diazo-compounds, such as diazo imines 2’, have recently
Figure 1. 1,3,5-Trioxane (1) and related derivatives of pharmaceutical inter-
est.
[
7]
drawn considerable attention (Scheme 1). These compounds
are formed by ring-chain tautomerization of N-sulfonyl 1,2,3-tri-
azoles (2), which are easily accessible through the copper(I)-
catalyzed 1,3-dipolar cycloaddition of sulfonyl azides to termi-
+
+
[
a] Dr. J. Pospech, Dr. R. Ferraccioli, Dr. H. Neumann, Prof. Dr. M. Beller
Leibniz-Institut für Katalyse an der Universität Rostock e.V.
Albert-Einstein-Straße 29
[8]
nal alkynes. In the presence of a di-rhodium tetracarboxylate
catalyst, compounds 2’ give rise to the corresponding metal-
bound a-imino carbenes (3), which react with weak unsaturat-
ed or protic nucleophiles.
18059 Rostock (Germany)
E-mail: Matthias.beller@catalysis.de
+
[
b] Dr. R. Ferraccioli
Clearly, compound 1 is a challenging coupling partner for
compound 3: the lone pairs of electrons on the oxygen atoms
impart nucleophilic character onto compound 1, whilst the
same oxygen atoms might also facilitate CÀH cleavage
CNR-Istituto di Scienze e Tecnologie Molecolari (ISTM)
Via C. Golgi 19, 20133
Milano (Italy)
+
[
] These authors contributed equally to this work.
[
9]
through an inductive effect, thus favoring CÀH insertion.
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/asia.201500493.
Chem. Asian J. 2015, 10, 2624 – 2630
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Full Paper
[a]
Table 1. Optimization of the reaction conditions for the model system.
II
[b]
[c]
Rh catalyst
Solvent
GC yield
1
2
3
4
5
6
7
8
9
1
[Rh (OAc)
2
4
]
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
10
<5
60
<5
55
45
10
72
<5
15
[Rh
2 4
(Oct) ]
[Rh
2
4
(Piv) ]
[Rh
[Rh
2
(TPA)
4
]
2
4
(Ad) ]
[Rh
[Rh
[Rh
[Rh
[Rh
[Rh
2
(esp)
2
]
2
(Piv)
(Piv)
(Piv)
(Piv)
(Piv)
4
]
]
]
]
]
CH
2
Cl
2
2
2
2
2
4
4
4
4
CHCl
3
n-heptane
cyclohexane
toluene
0
Scheme 1. a) Aim of this work; b) developments by the groups of Fokin and
11
54
Lacour.
[
a] Reaction conditions: compound 2a (0.5 mmol), compound
II
1
[
(2.5 mmol), Rh catalyst (1 mol%), dry solvent (2.0 mL), 408C, 16 h;
2a]=0.5m. [b] 1,2-DCE=1,2-dichloroethane; Ms=methanesulfonyl; Ac=
acetyl; Oct=octanoate; Piv=pivalate; TPA =triphenylacetate; Ad=1-ada-
mantanecarboxylate; esp=a,a,a’,a’-tetramethyl-1,3-benzenedipropa-
Herein, we report the first application of compound 1 as
a coupling partner for the rhodium(II)-catalyzed decomposition
of N-mesyl 1,2,3-triazoles (2), thereby affording 1,3,5,7-trioxazo-
nine derivatives 4, which are a new class of N,O-heterocycles
noate. [c] Determined through GC analysis of the crude reaction mixture.
(
Scheme 1a).
The synthesis of medium-sized ring systems continues to at-
tract significant attention because of the broad abundance of
this scaffold in natural and synthetic products, as well as the
[
10]
therapeutic success of these compounds, such as taxol and
[11]
a number of polycyclic ethers.
Clearly, the formation of
seven-to-11-membered rings constitutes a significant synthetic
challenge, because it is often hampered by adverse entropic or
Scheme 2. Formation of compound 5.
[12]
unfavorable transannular interactions. Until now, these com-
pounds have typically been obtained through macrocycliza-
A brief solvent screening revealed that halogenated sol-
[
13]
tion, fragmentation, ring expansion, and ring-closing meta-
vents, such as 1,2-DCE and CHCl , were superior to toluene
3
[
14]
thesis reactions.
and other aliphatic solvents that were tested (Table 1, en-
The catalytic decomposition of N-sulfonyl triazoles in the
tries 7–11): in CHCl , the yield of compound 4a increased to
3
presence of cyclic ethers was first observed by the groups of
72% (Table 1, entry 8). Higher reaction temperatures (up to
808C) did not improve the selectivity. Notably, the complete
exclusion of water was necessary for a selective transformation.
Water, as a nucleophile, competes with compound 1 in the re-
action with compound 3, thereby leading to a-aminoketone
[15]
Fokin and Gevorgyan (Scheme 1b). While this work was in
progress, Lacour and co-workers reported related reactions
with cyclic acetals, such as 1,3-dioxolane and 1,3-dioxane, to
give eight- and nine-membered dioxazocines and dioxazo-
[16]
[17]
1
nines, respectively (Scheme 1b).
5
along with compound 4a (5/4a=25:75, by H NMR analy-
sis; Scheme 2).
Electronic and steric variation of the sulfonyl derivatives
played a role in determining the reactivity of compound 2.
Under the optimized conditions (Table 1, entry 8), both benzyl-
sulfonyl and isopropylsulfonyl triazoles 2b and 2c reacted
smoothly with compound 1, thereby giving the corresponding
nine-membered-ringed derivatives (4b and 4c, respectively),
the latter in moderate yield, probably owing to the increased
steric encumbrance of the resulting di-rhodiumÀcarbene inter-
mediate (3; Table 2, entries 2–3). Surprisingly, on switching to
1-tosyltriazole (2d), no transformation occurred (Table 2,
entry 4). Apparently, the use of 1-alkylsulfonyl-triazoles as car-
bene precursors was crucial in the reaction with compound 1.
In contrast, 1-arylsulfonyl triazoles have been reported to give
the best results with 1,3-dioxolane or 1,2-dioxane in the pres-
Results and Discussion
First, we investigated the reaction of compound 1 with com-
1
2
pound 2a (R =Ph, R =Ms) in detail in the presence of a series
of di-rhodium catalysts (Table 1, entries 1–6). A preliminary
screening found that the most-promising results were ob-
tained by using [Rh (Piv) ] (1 mol%) as a catalyst, which pro-
2
4
moted the complete consumption of compound 2a and the
formation of nine-membered N,O-heterocycle 4a in fair yield
(
Table 1, entry 3). The use of more-sterically hindered [Rh (Ad) ]
2 4
and [Rh (esp) ] only afforded the product in slightly lower
2
2
yields (Table 1, entries 5 and 6, respectively), whilst the pres-
ence of [Rh (OAc) ], [Rh (Oct) ], and [Rh (TPA) ] afforded
2
4
2
4
2
4
modest conversions (Table 1, entries 1, 2, and 4, respectively).
Chem. Asian J. 2015, 10, 2624 – 2630
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[a,b]
Table 2. Catalytic reactions using different 1-sulfonyl-4-phenyl-1,2,3-tria-
zoles.
Table 3. Catalytic reactions using different 1-mesyl-4-aryl-triazoles.
[a]
2
[b]
[c]
R
Conversion [%]
Yield [%]
1
2
3
4
Me
Bn
iPr
Tol
2a (100)
2b (100)
2c (100)
2d (100)
4a (72)
4b (61)
4c (40)
4d (–)
[
1
0
a] Reaction conditions: compound 2a (0.2 mmol), compound
II
(1.0 mmol), Rh catalyst (1 mol%), dry CHCl
3
(0.4 mL), 408C, 16 h; [2a]=
1
.5m. [b] Determined through H NMR analysis of the crude reaction mix-
ture. Bn=benzyl, Tol =tolyl. [c] Yield of the isolated product.
[
15,16]
ence of [Rh (OAc) ] as a catalyst in toluene at 1008C.
It is
2
4
important to note that this reaction is orthogonal to the previ-
ously reported procedures.
Next, the general scope of the reaction with 1-mesyl tria-
zoles that contained various substituents at the C4 carbon
atom was examined. Triazoles that contained mono- and di-
substituted 4-aryl substituents with different electronic fea-
tures were well-tolerated (Table 3). Substrates that contained
electron-donating groups, such as Me, tBu, and MeO groups,
at the meta or para positions of the benzene ring afforded the
corresponding products (4e, 4 f, 4h, and 4i) in fair-to-good
yields. Triazoles that contained bulkier substituents, such as
2
,5-dimethylphenyl or 6-methoxynaphtyl groups, led to the
corresponding products (4g and 4l) in moderate yields. Elec-
tron-withdrawing halide functional groups, which are com-
monly used in cross-coupling reactions, were also well-tolerat-
ed and substrates that contained C4 aryl groups that con-
tained chloro, bromo, and fluoro groups at the meta and/or
para positions allowed us to obtain the corresponding prod-
ucts (4m–4q) in fair-to-good yields.
[a] Reaction conditions: compound 2 (0.2 mmol), compound 1 (5 equiv),
Rh (Piv) ] (1 mol%), dry CHCl (0.4 mL), 408C,16 h; [2]=0.5m. In all of the
examples, complete conversion of compound 2 was observed by H NMR
analysis of the crude reaction mixture.is not Lacour [b] Yield of the isolated
product. [c] Compound 1 (10 equiv). [d] The reaction was performed at
508C.
[
2
4
3
1
Disappointingly, attempts to extend the scope of the reac-
1
tion to include 4-heteroaryl- (R =3-thiophenyl) and 4-alkyl-
1
substituted triazoles (R =hexyl and 1-cyclohexenyl) failed. In
each case, the reaction led to a complex mixture that only con-
1
13
tained trace amounts of the desired products. H and C NMR
analysis was consistent with the structures assigned to com-
pounds 4, as further confirmed by X-ray diffraction studies
(
Figure 2).
According to the mechanism reported by Lacour and co-
workers, the reaction likely proceeds through the formation of
1,2]-dipolar rhodium-associated oxonium ylide 6, which results
[
from the coupling of O-nucleophile 1 to the transient RhÀcar-
Figure 2. X-ray data and structure of compound 4 f.
[19]
bene species 3 (Scheme 3). Subsequent trioxanyl ring open-
ing occurs through CÀO bond cleavage, assisted by one of the
unshared electronic pair of the non-bonded oxygen atom. The
In principle, compounds 4 can be synthesized in a one-pot,
two-step procedure directly from mesylazide and a terminal
alkyne, thereby avoiding the necessary isolation of compound
2 (Scheme 4). For instance, a 0.25m solution of compound 2a
[19]
resulting unsaturated oxo-carbenium ion (7) is then trapped
by the nitrogen atom of the tethered sulfonylimino group
through a 9-endo-trig cyclization to form compound 4.
Chem. Asian J. 2015, 10, 2624 – 2630
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nylazide are known compounds and were prepared as described in
[21]
the literature.
Caution: Azides are potentially hazardous compounds and ade-
quate safety measures should be taken. Melting points (m.p.) were
recorded on a Stuart melting point apparatus by using open glass
capillaries and are uncorrected. IR spectra were recorded on
a BRUKER ALPHA-P spectrometer. Absorption is given in wavenum-
Scheme 3. Proposed mechanism.
À1
bers (cm ). The spectra were recorded within the range 4000–
À1
4
00 cm and the following abbreviations are used for characteriza-
tion: s (strong), m (medium), w (weak). NMR spectra were recorded
on Bruker Avance 300 (300 MHz) and 400 (400 MHz) spectrometers.
Chemical shifts are reported relative to the solvent peaks: CDCl ,
3
1
13
1
d=7.26 ppm ( H) and 77.00 ppm ( C); CD Cl , d=5.36 ppm ( H)
2
2
1
3
and 53.9 ppm ( C). All of the measurements were performed at RT.
GCMS analysis was performed on an Agilent 5973 chromatography
mass-selective detector system. HRMS was performed on MAT
Scheme 4. Synthesis of compound 4a through a one-pot, two-step proce-
dure.
9
5XP (EI) and Agilent 6210 Time-of-Flight LC/MS (ESI) systems.
Crystallographic data were collected on a BRUKER KAPPA APEX II
DUO diffractometer. The structures was solved by using direct
methods and refined by full-matrix least-squares procedures on F2
with the SHELXTL software package. XP (BRUKERAXS) was used
for graphical representation. Displacement ellipsoids are set at the
in CHCl , which was formed from a copper(I)Àthiophene-2-car-
3
boxylate (CuTC)-catalyzed cycloaddition reaction, was sequen-
[22]
tially treated with compound 1 and [Rh (Piv) ]. The resulting
2
4
reaction mixture was heated at 508C to give compound 4a in
9% yield (see the Experimental Section). Apparently, the
3
0% probability level.
4
metal catalysts did not interfere with each other. Temperature
control at the stage of triazole synthesis turned out to be nec-
essary to obtaining a reproducible transformation.
Synthesis of 4
General procedure: 1,3,5-Trioxane (1; 90 mg, 1.0 mmol) was added
to a solution of triazole 2 (0.2 mmol) in dry CHCl3 (0.4 mL). The
mixture was stirred for 2 min at RT and [Rh (Piv) ] (1.2 mg, 1 mol%)
Conclusion
2
4
was added. The resulting reaction mixture was stirred for 16 h at
08C, before being concentrated under reduced pressure. The
In conclusion, readily available 1,3,5-trioxane is an effective
4
II
coupling partner in the Rh -catalyzed decomposition of 1-
crude residue was purified by chromatography through a short
pad of neutral aluminum oxide (EtOAc/pentane).
mesyl 1,2,3-triazoles (2). Reaction with the corresponding aza-
vinylcarbene intermediate (3) triggers the ring opening of
compound 1, which then takes part in the construction of
a new class of nine-membered heterocycles (4) that contain
the unusual OÀCÀOÀCÀOÀC atom sequence, which is other-
wise hardly accessible. Interestingly, the use of N-alkylsulfonyl
(Z)-7-(Methylsulfonyl)-9-(phenyl)-6,7-dihydro-1,3,5,7-trioxazo-
nine (4a)
1
Yield 72% (41 mg); m.p. 101–1028C; H NMR (300 MHz, CDCl
.47–7.41 (m, 2H), 7.41–7.31 (m, 3H), 6.51 (s, 1H), 5.54 (s, 2H), 5.00
): d=
3
7
1
,2,3-triazoles instead of N-arylsulfonyl 1,2,3-triazoles as metalÀ
1
3
(
s, 2H), 4.93 (s, 2H), 3.13 ppm (s, 3H); C NMR (75 MHz, CDCl ): d=
3
carbene precursors is decisive for the success of the reaction.
A variety of electron-rich and electron-poor substituents at the
C4 position of compound 2 are well-tolerated. The combina-
tion of copper(I)-catalyzed 1,3-dipolar cycloaddition and rho-
dium(II)-catalyzed denitrogenative coupling led to compound
1
42.5 (Cq), 133.4 (Cq), 128.9 (CH), 128.9 (CH), 125.9 (CH), 113.8
(
CH), 96.7 (CH ), 93.9 (CH ), 77.9 (CH ), 41.9 ppm (CH ); IR (ATR,
2
2
2
3
neat): n˜ =2964 (w), 2936 (w), 2895 (w), 1343 (s), 1147 (s), 1100 (m),
À1
1
2
056 (s), 929 (s), 773 (s), 697 (m), 509 cm (s); MS (GCMS): m/z (%):
85 (13) [M] , 255 (8), 225 (6), 146 (100), 105 (78), 91 (83), 77 (37);
+
+
4
a in 49% yield through a one-pot, two-step procedure from
HRMS (ESI-TOF): m/z calcd for C H NSO : 308.0563 [M+Na] ;
12
15
5
1
-mesylazide and phenylacetylene, thus confirming the practi-
found: 308.0566.
cal and synthetic utility of this new reaction.
(Z)-7-(Benzylsulfonyl)-9-phenyl-6,7-dihydro-1,3,5,7-trioxazo-
nine (4b)
Experimental Section
1
Yield 61% (44 mg); m.p. 101–1028C; H NMR (300 MHz, CD Cl ):
2
2
General Information
d=7.60 (m, 2H), 7.46 (m, 3H), 7.36 (m, 3H), 7.20 (m, 2H), 6.25 (s,
The reactions that were catalyzed by di-rhodium catalysts were
performed under an argon atmosphere. Anhydrous solvents
1H), 5.66 (s, 2H), 5.09 (s, 2H), 4.93 (s, 2H), 4.54 ppm (s, 2H);
13
C NMR (75 MHz, CD Cl ): d=138.3 (Cq), 134.1 (Cq), 131.8 (CH),
2
2
(
CHCl , 1,2-DCE, and toluene) were purchased from Sigma–Aldrich
129.2 (CH), 129.1 (CH), 128.8 (Cq), 128.6 (CH), 126.0 (CH), 114.4
(CH), 97.6 (CH ), 94.1 (CH ), 78.2 (CH ), 61.0 ppm (CH ); IR (ATR,
neat): n˜ =3067 (w), 2989 (w), 2926 (w), 1665 (m), 1446 (m), 1342
3
and used without further purification. All of the chemicals were
purchased from Acros, TCI, or Sigma–Aldrich and used as received
unless otherwise stated. 1,3,5-Trioxane was purified by sublimation
and stored under an argon atmosphere. [Rh (Piv) ], [Rh (Oct) ],
and [Rh (Ad) ] were synthesized according to reported proce-
2
2
2
2
(s), 1227 (m), 1139 (s), 1074 (s), 1048 (s), 996 (m), 913 (s), 877 (s),
[7e]
[20]
À1
847 (m), 788 (s), 769 (s), 696 cm (s); MS (GCMS): m/z (%): 361 (1)
2
4
2
4
[20]
+
[M] , 146 (33), 105 (27), 91 (100), 77 (25); HRMS (ESI-TOF): m/z
2
4
+
dures. Methansulfonylazide, benzylsulfonylazide, and toluensulfo-
calcd for C H NO S: 384.08761 [M+Na] ; found: 384.08812.
18
19
5
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ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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(Z)-7-(Isopropylsulfonyl)-9-phenyl-6,7-dihydro-1,3,5,7-trioxazo-
(Cq), 143.4 (Cq), 130.3 (Cq), 125.8 (CH), 125.7 (CH), 113.21 (CH), 96.5
(
CH ), 93.9 (CH ), 77.9 (CH ), 41.7 (CH ), 34.7 (Cq), 31.3 ppm (CH );
2 2 2 3 3
nine (4c)
IR (ATR, neat): n˜ =2956 (s), 1606 (w), 1408 (w), 1327 (s), 1062 (m),
833 (m), 620 (w), 510 (s), 442 cm (w); MS (GCMS): m/z (%): 341 (5)
1
Yield 40% (25 mg); m.p. 89–908C; H NMR (300 MHz, CD Cl ): d=
À1
2
2
7
2
.34–7.19 (m, 5H), 6.50 (s, 1H), 5.51 (s, 2H), 4.92 (s, 2H), 4.81 (s,
H), 3.34 (sep, J=9 Hz, 1H), 1.35 ppm (d, J=9 Hz, 6H); C NMR
+
[M] , 202 (68), 161 (40), 147 (100), 132 (10), 118 (23), 91 (15); HRMS
13
+
(
ESI-TOF): m/z calcd for C H NO S: 364.11891 [M+Na] ; found:
16
23
5
(
75 MHz, CD Cl ): d=137.8 (Cq), 134.4 (Cq), 129.1 (CH), 128.5 (CH),
2 2
364.11923.
1
1
1
25.9 (CH), 115.0 (CH), 97.3 (CH ), 94.2 (CH ), 77.9 (CH ), 56.4 (CH),
2 2 2
6.6 ppm (CH ); IR (ATR, neat): n˜ =2983 (w), 2919 (w), 1665 (m),
444 (m), 1329 (s), 1225 (s), 1145 (s), 1051 (s), 995 (m), 951 (m), 901
3
(
Z)-7-(Methylsulfonyl)-9-(p-anisyl)-6,7-dihydro-1,3,5,7-trioxazo-
À1
nine (4i)
(
(
s), 823 (m), 761 (s), 690 (s), 646 cm (m); MS (GCMS): m/z (%): 313
3), 146 (65), 105 (52), 91 (100), 77 (52), 43 (49); HRMS (ESI-TOF): m/
1
Yield: 60% (38 mg); H NMR (300 MHz,): d=7.29 (d, J=9.0 Hz, 2H),
6.84 (d, J=9.0 Hz, 2H), 6.28 (s, 1H), 5.38 (s, 2H), 4.92 (d, J=
+
z calcd for C H NO S: 336.08761 [M+Na] ; found: 336.08805.
1
4
19
5
13
1
2.7 Hz, 4H), 3.76 (s, 3H), 3.05 ppm (s, 3H); C NMR (75 MHz,
CDCl ): d=160.4 (Cq), 144.5 (Cq), 127.6 (CH), 125.3 (Cq), 114.2 (CH),
12.5 (Cq), 96.4 (CH ), 93.7 (CH ), 78.1 (CH ), 55.4 (CH ), 41.7 ppm
(Z)-7-(Methylsulfonyl)-9-(m-tolyl)-6,7-dihydro-1,3,5,7-trioxazo-
3
1
nine (4e)
2
2
2
3
(
CH ); IR (ATR, neat): n˜ =2962 (w), 2840 (w), 1683 (m), 1599 (s),
3
1
À1
Yield 74% (45 mg); m.p. 91–928C; H NMR (300 MHz, CDCl ): d=
3
1511 (s), 1147 (s), 830 (w), 506 cm (m); MS (GCMS): m/z (%): 315
(
175 (69); HRMS (EI): m/z calcd for C H NO S: 316.08548 [M+H] ;
13 17 6
+
7
3
.22 (m, 4H), 6.42 (s, 1H), 5.46 (s, 2H), 4.94 (s, 2H), 4.87 (s, 2H),
.07 (s, 3H), 2.30 ppm (s, 3H); C NMR (75 MHz, CDCl ): d=142.7
10) [M] , 252 (19), 250 (13), 235 (11), 207 (21), 177 (19), 176 (100),
1
3
+
3
(
(
Cq), 138.5 (Cq), 133.2 (Cq),129.6 (CH), 128.7 (CH), 126. 5 (CH), 123
CH), 113.5 (CH), 96.6 (CH ), 93.8 (CH ), 77.8 (CH ), 41.7 (CH ),
found: 316.08549.
2
2
2
3
2
1
1
6
1.4 ppm (CH ); IR (ATR, neat): n˜ =3101 (w), 2983 (w), 2911 (w),
3
(
Z)-9-(6-Methoxynaphthalen-2-yl)-7-(methylsulfonyl)-6,7-dihy-
663 (m), 1476 (w), 1330 (s), 1218 (m), 1198 (m), 1146 (s), 1077 (s),
053 (s), 906 (s), 827 (s), 792 (s), 770 (s), 722 (w), 708 (w), 685 (s),
dro-1,3,5,7-trioxazonine (4l)
À1
+
46 cm (m); MS (GCMS): m/z (%): 299 (4) [M] , 160 (55%), 119
1
Yield 39% (28.5 mg); m.p. 162–1638C; H NMR (300 MHz, CD Cl ):
d=7.75 (br d, 1H), 7.67–7.64 (m, 2H), 7.42 (dd, J=9.0, 3.0 Hz, 1H),
7.08–7.04 (m, 2H), 6.49 (s, 1H), 5.45 (s, 2H), 4.92 (s, 2H), 4.89 (s,
2
1
2
2
(
53%), 105 (100%), 91 (50%), 79 (27%); HRMS (ESI-TOF): m/z calcd
+
for C H NO S: 322.07196 [M+Na] ; found: 322.07228.
1
3
17
5
13
H), 3.81 (s, 3H), 3.05 ppm (s, 3H); C NMR (75 MHz, CD Cl ): d=
2 2
58.7 (Cq), 142.8 (Cq), 135.1 (Cq), 130.0 (CH), 129. 127.7 (CH), 125.2
(Z)-7-(Methylsulfonyl)-9-(p-tolyl)-6,7-dihydro-1,3,5,7-trioxazo-
(
(
CH), 124.3 (CH), 119.8 (CH), 113.7 (CH), 106.1 (CH), 97.1 (CH ), 94.4
CH ), 78.3 (CH ), 55.7 (CH ), 42.0 ppm (CH ); IR (ATR, neat): n˜ =
nine (4 f)
2
2
2
3
3
1
Yield 72% (43 mg); m.p. 122–1238C; H NMR (300 MHz, CDCl ): d=
3016 (w), 2966 (w), 2926 (w), 1602 (m), 1845 (m), 1342 (s), 1206 (s),
1161 (s), 1150 (s), 1107 (s), 1055 (s), 1023 (s), 969 (s), 905 (s), 821 (s),
767 cm (s); MS (GCMS): m/z (%): 365 (11) [M] , 226 (50), 185 (54),
171 (100), 142 (21); HRMS (ESI-TOF): m/z calcd for C H NO S:
3
7
2
.33 (d, J=8.2 Hz, 2H), 7.17 (d, J=7.8 Hz, 2H), 6.45 (s, 1H), 5.50 (s,
H), 5.00 (s, 2H), 4.94 (s, 2H), 3.13 (s, 3H), 2.36 ppm (s, 3H);
À1
+
13
C NMR (75 MHz, CDCl ): d=143.5 (Cq), 139.1 (Cq), 130.4 (Cq),
3
17 19
6
+
1
4
1
8
2
29.6 (CH), 126.0 (CH), 113.2 (CH), 96.6 (CH ), 93.9 (CH ), 77.8 (CH ),
388.08253 [M+Na] ; found: 388.08282.
2
2
2
1.8 (CH ), 21.4 ppm (CH ); IR (ATR, neat): n˜ =2956 (w), 2901 (w),
3
3
332 (m), 1323 (m), 1145 (m), 1145 (s), 1109 (s), 1072 (s), 927 (s),
(Z)-7-(Methylsulfonyl)-9-(4-bromophenyl)-6,7-dihydro-1,3,5,7-
À1
+
14 (s), 767 (m), 516 cm (s); MS (GCMS): m/z (%): 299 (6) [M] ,
trioxazonine (4m)
69 (3), 160 (71), 119 (59), 105 (100), 91 (38); HRMS (ESI-TOF): m/z
+
1
calcd for C H NO S: 299.0822 [M] ; found: 299.0823.
Yield 70% (50.5 mg); m.p. 141–1428C; H NMR (300 MHz, CDCl ):
1
3
17
5
3
d=7.49 (d, J=8.7 Hz, 2H), 7.30 (d, J=8.7 Hz, 2H), 6.53 (s, 1H), 5.56
1
3
(
(
s, 2H), 5.01 (s, 2H), 4.90 (s, 2H), 3.13 ppm (s, 3H); C NMR
(Z)-9-(2,5-Dimethylphenyl)-7-(methylsulfonyl)-6,7-dihydro-
75 MHz, CDCl ): d=140.4 (Cq), 132.6 (Cq), 132.1 (Cq), 127.3 (CH),
3
1
,3,5,7-trioxazonine (4g)
1
22.8 (CH), 114.2 (CH), 96.9 (CH ), 94.0 (CH ), 77.8 (CH ), 42.0 ppm
2 2 2
1
Yield 48% (30 mg); m.p. 87–888C; H NMR (300 MHz, CD Cl ): d=
(CH ); IR (ATR, neat): n˜ =2961 (w), 2895 (w), 1670 (w), 1478 (w),
2
2
3
7
2
.06 (br s, 1H), 7.015 (br d, 2H), 6.03 (s, 1H), 5.46 (s, 2H), 4.91 (s,
H), 4.68 (s, 2H), 3.07 (s, 3H), 2.26 (s, 3H), 2.25 ppm (s, 3H);
C NMR (75 MHz, CD Cl ): d=143.8 (Cq), 135.7 (Cq), 134.9 (Cq),
1341 (s), 1219 (m), 1145 (s), 1049 (s), 998 (s), 969 (s), 904 (s), 832 (s),
812 (s), 512 (s), 475 cm (m); MS (GCMS): m/z (%): 363 (6) [M] ,
À1
+
1
3
2
2
333 (5), 303 (2), 224 (100), 183 (57), 169 (99), 155 (33); HRMS (ESI-
+
1
9
32.6 (Cq), 131.6 (CH), 130.9 (CH), 130.3 (CH), 115.5 (CH), 97.2 (CH2),
3.1 (CH ), 78.7 (CH ), 41.7 (CH ), 20.9 (CH ), 20.0 ppm (CH ); IR
TOF): m/z calcd for C H BrNO S: 303.0571 [M] ; found: 303.0568.
12
14
5
2
2
3
3
3
(
1
(
1
ATR, neat): n˜ =2964 (w), 2924 (w), 2902 (w), 1686 (m), 1352 (m),
325 (s), 1223 (m), 1143 (s), 1077 (s), 1051 (s), 973 (s), 920 (s), 895
(
Z)-9-(3-Fluorophenyl)-7-(methylsulfonyl)-6,7-dihydro-1,3,5,7-
trioxazonine (4n)
À1
+
s), 817 (s), 772 cm (s); MS (GCMS): m/z (%): 313 (4) [M] , 174 (51),
33 (41), 119 (100), 105 (18); HRMS (ESI-TOF): m/z calcd for
1
Yield: 80% (48.5 mg); m.p. 118–1198C; H NMR (300 MHz, CDCl ):
d=7.33 (td, J=8.0, 5.8 Hz, 1H), 7.22 (ddd, J=7.8, 1.7, 1.1 Hz, 1H),
3
+
C H NO S: 336.08761 [M+Na] ; found: 336.08768.
14
19
5
7
5
.15–7.09 (m, 1H), 7.01 (tdd, J=8.3, 2.6, 1.1 Hz, 1H), 6.59 (s, 1H),
.59 (d, J=2.1 Hz, 2H), 5.02 (s, 2H), 4.92 (s, 2H), 3.13 ppm (s, 3H);
(
1
Z)-9-(4-(tert-Butyl)phenyl)-7-(methylsulfonyl)-6,7-dihydro-
,3,5,7-trioxazonine (4h)
13
1
C NMR (75 MHz, CDCl ): d=163.2 (d, J =246.3 Hz; Cq), 139.8
3
(C,F)
4
3
3
(
d, J( =2.7 Hz; Cq), 136.2 (d, J =7.6 Hz; Cq), 130.5 (d, J
=
C,F)
(C,F)
(C,F)
1
4
2
Yield 64% (44 mg); m.p. 112–1138C; H NMR (300 MHz, CDCl ): d=
7
3
8.4 Hz; CH), 121.4 (d, J =2.9 Hz; CH), 115.6 (d, J =21.4 Hz;
CH), 114.7 (CH), 112.6 (d, J( =23.1 Hz; CH), 97.0 (CH ), 94.1 (CH ),
77.8 (CH2), 42.0 ppm (CH3);
3
(C,F)
(C,F)
2
.19 (m, 4H), 6.39 (s, 1H), 5.43 (s, 2H), 4.92 (s, 2H), 4.88 (s, 2H),
C,F)
2
2
1
3
19
.04 (s, 3H), 1.25 ppm (s, 9H); C NMR (75 MHz, CDCl ): d=152.2
F NMR (282 MHz, CDCl3): d=
3
Chem. Asian J. 2015, 10, 2624 – 2630
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ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
À111.9 ppm; IR (ATR, neat): n˜ =3015 (w), 2925 (w), 1361 (m), 1347
Synthesis of 2
(
m), 1146 (s), 1052 (m), 968 (m), 906 8 (s), 795 8 (m), 768 (s);
À1
+
N-Sulfonyl 1,2,3-triazoles (2) were prepared according to the previ-
5
1
08 cm (s); MS (GCMS): m/z (%): 303 (3) [M] , 273 (4), 164 (89),
ously reported CuTC-catalyzed azide-alkyne cycloaddition (CuAAC)
23 (53), 109 (100), 95 (42); HRMS (ESI-TOF): m/z calcd for
C H NFO S: 303.0571 [M] ; found: 303.0568.
[23]
+
procedure.
.01 mmol, 5 mol%) was added to a stirring solution of the alkyne
2.0 mmol) in toluene (5 mL) at RT. After stirring for 5 min, a solu-
Copper(I) thiophene-2-carboxylate (CuTC; 0.019 g,
12
14
5
0
(
tion of the sulfonyl azide (2.0 mmol) in toluene (3 mL) was added
dropwise to the resulting suspension. The reaction mixture was
concentrated under reduced pressure and filtered through a short
plug of silica gel to remove the copper catalyst (EtOAc/pentane,
3:10). Removal of the solvent under vacuum gave a solid residue
that was crystallized from EtOAc/pentane to afford the desired
(
Z)-9-(4-Fluorophenyl)-7-(methylsulfonyl)-6,7-dihydro-1,3,5,7-
trioxazonine (4o)
1
Yield: 57% (34.5 mg); m.p. 113–1148C; H NMR (300 MHz, CD Cl ):
d=7.36 (m, 2H), 7.0 (m, 2H), 6.34 (s, 1H), 5.42 (s, 2H), 4.91 (s, 2H),
2
2
1
3
4
.83 (s, 2H), 3.02 ppm (s, 3H); C (75 MHz, CD Cl ): d=163.4 (d,
2 2
1
4
[25]
[22]
[23]
[22]
[25]
J(C,F) =246 Hz; Cq), 141.8 (Cq), 130.0 (d, J =3.0 Hz; Cq), 128.1 (d,
product. Data for compounds 2a, 2b,
2c,
2d,
2 f,
2i,
(C,F)
3
2
[23]
[23]
[26]
[27]
[25]
[24]
J(C,F) =7.5 Hz; CH), 116.1 (d, J(C,F) =22.5 Hz; CH), 113.9 (CH), 97.1
2l,
viously.
2m,
2n,
2o,
and 2p have been reported pre-
1
9
(
CH ), 94.1 (CH ), 78.2 (CH ), 42 ppm (CH ); F NMR (282 MHz,
2 2 2 3
CD Cl ): d=À113.0 ppm; IR (ATR, neat): n˜ =2903 (w), 1600 (w),
2
2
1
506 (w), 1327 (s), 1217 (m), 1150 (s), 1063 (s), 1050 (s), 932 (s), 900
À1
1-(Methylsulfonyl)-4-(m-tolyl)-1H-1,2,3-triazole (2e)
(
[
m), 833 (m), 772 (s), 717 cm (m); MS (GCMS): m/z (%): 303 (5)
M] , 164 (100), 123 (56), 109 (90), 95 (25); HRMS (ESI-TOF): m/z
+
1
Yield: 85% (402 mg); m.p. 82–838C; H NMR (CD Cl , 400 MHz): d=
2
2
+
calcd for C H FNO S: 326.04689 [M+Na] ; found: 326. 04717.
8.37 (s, 1H), 7.76 (br s, 1H), 7.69 (br d, J=8.0 Hz, 1H), 7.40 (t, J=
1
2
14
5
8
3
.0 Hz, 1H), 7.28 (br d, J=8.0 Hz, 1H), 3.59 (s, 3H), 2.46 ppm (s,
13
H); C NMR (75 MHz, CD Cl ): d =147.4 (Cq), 139.1 (Cq), 130.0
2
2
(
Z)-7-(Methylsulfonyl)-9-(4-chlorophenyl)-6,7-dihydro-1,3,5,7-
(
(
CH), 128.9 (CH), 128.6 (CH), 126.6 (CH), 123.1 (CH), 119.3 (CH), 42.8
CH ), 21.1 ppm (CH ); IR (ATR, neat): n˜ =3140, 3013, 2972, 1626,
trioxazonine (4p)
3
3
1
1590, 1489, 1478, 1385, 1373, 1352, 1231, 1176, 1090, 1041, 1008,
Yield 65% (42 mg); m.p. 110–111 8C; H NMR (300 MHz, CDCl ): d=
3
À1
9
81, 955, 837, 789, 775, 715, 700, 645 cm ; HRMS (ESI-TOF): m/z
7
3
.29 (m, 4H), 6.45 (s, 1H), 5.49 (s, 2H), 4.94 (s, 2H), 4.84 (s, 2H),
.06 ppm (s, 3H); C NMR (75 MHz, CDCl ): d=140.5 (Cq), 134.6
+
1
3
calcd for C10H N O S: 238.06447 [M+H] ; found: 238.06458.
11 3 2
3
(
Cq), 132.0 (Cq), 129.0 (CH), 127.0 (CH), 114.1 (CH), 96.8 (CH ), 93.9
2
(
1
(
1
CH ), 77.8 (CH ), 41.9 (CH ); IR (ATR, neat): n˜ =2975 (w), 2795 (w),
4-(2,5-Dimethylphenyl)-1-(methylsulfonyl)-1H-1,2,3-triazole
2g)
2
2
3
À1
636 (w), 1488 (m), 1325 (s), 1151 (s), 833 (m), 688 (w), 511 cm
(
+
m); MS (GCMS): m/z (%): 319 (5) [M] , 180 (82), 139 (61), 125 (100),
1
+
Yield: 77% (386 mg); m.p. 88–898C; H NMR (CD Cl , 300 MHz): d=
2 2
11 ppm (36); HRMS (EI): m/z calcd for C H NO S: 319.0281 [M] ;
1
2
14
5
8
9
.25 (s, 1H), 7.67 (br s, 1H), 7.24 (dd, J=9.0 Hz, 1H), 7.19 (br d, J=
.0 Hz, 1H), 3.61 (s, 3H), 2.47 (s, 3H), 2.41 ppm (s, 3H); C NMR
found: 319.0274.
1
3
(
75 MHz, CD Cl ): d=147.1 (Cq), 136.3 (Cq), 133.3 (Cq), 131.4(CH),
2 2
(Z)-9-(3,4-Dichlorophenyl)-7-(methylsulfonyl)-6,7-dihydro-
130.2 (CH), 129.9 (CH), 128.2 (Cq), 121.5 (CH), 43.2 (CH ), 21.0 ppm
3
(
1
CH ); IR (ATR, neat): n˜ =3163, 3013, 2929, 2870, 1504, 1379, 1242,
1
,3,5,7-trioxazonine (4q)
3
180, 1149, 1090, 1029, 1004, 991, 975, 956, 900, 861, 834, 809,
1
Yield 68% (48 mg); m.p. 130--1318C; H NMR (300 MHz, CDCl ): d=
À1
+
3
764, 684, 638 cm ; MS (GCMS): m/z (%): 173 (100) [MÀSO Me] ,
2
7
6
.44 (d, J=2.4 Hz, 1H), 7.365 (d, J=8.4 Hz, 1H), 7.21–7.18 (m, 1H),
1
58 (29), 144 (47), 130 (72), 115 (75), 102 (35), 77 (51).
.52 (s, 1H), 5.54 (s, 2H), 4.96 (s, 2H), 4.83 (s, 2H), 3.07 ppm (s, 3H);
1
3
C NMR (75 MHz, CDCl ): d=137.9 (Cq), 134.0 (Cq), 133.1 (Cq),
3
1
-(Methylsulfonyl)-4-(tert-butylphenyl)-1H-1,2,3-triazole (2h)
1
9
2
32.4 (Cq), 130.8 (CH), 127.3 (CH), 124.7 (CH), 114.9 (CH), 97.0 (CH2),
4.0 (CH ), 77.6 (CH ), 42.0 ppm (CH ); IR (ATR, neat): n˜ =3088 (w),
996 (w), 2962 (w), 2889 (w), 1664 (m), 1470 (m), 1328 (s), 1218
1
2
2
3
Yield: 62% (345 mg); m.p. 119–1208C; H NMR (CD Cl , 300 MHz):
d=8.35 (s, 1H), 7.83 (br dt, J=9.0, 1.5 Hz, 2H), 7.54 (dt, J=9.0,
1
2
2
(
m), 1145 (s), 1050 (s), 1012 (s), 955 (s), 903 (s), 826 (s), 763 (s),
13
.5 Hz), 3.58 (s, 3H), 1.38 ppm (s, 9H); C NMR (CD Cl , 75 MHz):
2 2
À1
+
6
82 cm (m); MS (GCMS): m/z (%): 353 (5) [M+H] , 214 (100), 173
d=152.6 (Cq), 147.3 (Cq), 126.0 (CH), 125.9 (Cq), 125.8 (CH), 119.0
CH), 42.8 (CH3), 34.7 (Cq), 31.0 ppm (CH ); IR (ATR, neat): n˜ =3139
(
39), 159 (87), 145 (22), 109 (9); HRMS (ESI-TOF, m/z) calculated for
(
3
+
C H Cl NO S: 375.97837 [M+Na] ; found: 375.7777.
12
13
2
5
(w), 3039 (w), 2963 (m), 1495 (m), 1376 (s), 1321 (m), 1233 (w),
1
HRMS (ESI-TOF): m/z calcd for C H N O S: 280.11142 [M+H] ;
found: 280.11102.
À1
180 (s), 1119 (m), 997 (s), 947 (s), 840 (m), 815 (m), 768 cm (s);
+
13
17
3
2
Procedure for the One-Pot Synthesis of Compound 4a
Copper(I) thiophene-2-carboxylate (CuTC; 1.1 mg, 0.0057 mmol,
2
0
.5 mol%) was added to a stirring solution of the alkyne (23.5 mg,
.23 mmol) and methanesulfonyl azide (28 mg, 0.23 mmol) in dry
Synthesis of 4-(3,4-Dichlorophenyl)-1-(methylsulfonyl)-1H-
,2,3-triazole (2q)
1
CHCl (0.9 mL) at 08C under an argon atmosphere. The resulting
3
suspension was stirred at 08C for about 3 h and then was allowed
to warm to RT and stirred overnight. Compound 1 (104 mg,
A solution of 1,2-dichloro-ethynylbenzene (342 mg, 2.0 mmol) in
toluene (8 mL), copper(I) thiophene-2-carboxylate (CuTC; 0.019 g,
0.01 mmol, 5 mol%), and methanesulfonyl azide (0.243 g,
2.0 mmol), prepared as described above, was stirred at RT for 15 h.
A second addition of the catalyst (0.01 mmol) and methanesulfonyl
azide (2.0 mmol) was required to promote complete conversion of
the alkyne. The reaction mixture was stirred at RT for an additional
1
.15 mmol) and [Rh (Piv) ] (1.4 mg, 1 mol%) were added and the
2 4
reaction mixture was stirred at 508C for 9 h, before being concen-
trated at reduced pressure. The crude residue was purified by
column chromatography on neutral aluminum oxide (EtOAc/pen-
tane, 1:3) to give compound 4a (32 mg).
Chem. Asian J. 2015, 10, 2624 – 2630
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2629
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
2
7
8
7
4 h and worked-up as reported above to give the product. Yield:
5162; c) P. Anbarasan, D. Yadagiri, S. Rajasekar, Synthesis 2014, 46,
1
3004–3023. For recent selected examples, see: d) T. Miura, Y. Funakoshi,
3% (423 mg); m.p. 157–1588C; H NMR (CD Cl , 400 MHz): d=
2
2
T. Tanaka, M. Murakami, Org. Lett. 2014, 16, 2760–2763; e) S. W. Kwok,
L. Zhang, N. P. Grimster, V. V. Fokin, Angew. Chem. Int. Ed. 2014, 53,
.41 (s, 1H), 8.06 (d, J=2.0 Hz, 1H), 7.76 (d, J=8.0, 2.0 Hz, 1H),
1
3
.61 (d, J=8.0 Hz, 1H), 3.61 ppm (s, 3H); C NMR (CD Cl , 75 MHz):
2
2
3452–3456; Angew. Chem. 2014, 126, 3520–3524; f) X.-Y. Tang, Y.-S.
d=145.6 (Cq), 133.6 (Cq), 133.5 (Cq), 131.5 (CH), 129.3 (Cq), 128.2
CH), 125.7 (CH), 120.3 (CH), 43.2 ppm (CH ); IR (ATR, neat): n˜ =
Zhang, L. He, Y. Wei, M. Shi, Chem. Commun. 2015, 51, 133–136; g) S.
Chuprakov, B. T. Worrell, N. Selander, R. K. Sit, V. V. Fokin, J. Am. Chem.
Soc. 2014, 136, 195–202; h) Y. Jiang, X.-Y. Tang, M. Shi, Chem. Commun.
2015, 51, 2122–2125; i) X. Ma, F. Wu, X. Yi, H. Wang, W. Chen, Chem.
Commun. 2015, 51, 6862–6865; j) Y. Wang, X. Lei, Y. Tang, Chem.
Commun. 2015, 51, 4507–4510.
(
3
3
1
8
122, 3070, 3011, 2929, 1563, 1478, 1460, 1415, 1400, 1378, 1340,
326, 1275, 1257, 1235, 1179, 1137, 1103, 1030, 995, 976, 942, 907,
À1
18, 794, 771, 675, 636 cm ; HRMS (ESI-TOF): m/z calcd for
+
C H Cl N O S: 291.97088 [M+H] ; found: 291.97096.
9
7
2
3
2
[
[
8] a) M. Meldal, C. W. Tornoe, Chem. Rev. 2008, 108, 2952–3015; b) J. E.
Hein, V. V. Fokin, Chem. Soc. Rev. 2010, 39, 1302–1315; c) B. Schulze,
U. S. Schubert, Chem. Soc. Rev. 2014, 43, 2522–2571.
Acknowledgements
9] W. K. Busfield, D. Grice, I. D. Jenkins, J. Chem. Soc. Perkin Trans. 2 1994,
1
079–1086.
We thank the State of Mecklenburg-Vorpommern and the Bun-
desministerium für Bildung und Forschung (BMBF) for financial
support. We also thank Drs. C. Fischer, S. Buchholz, S. Scharei-
na, A. Koch, and S. Leiminger (LIKAT) for their analytical and
technical support.
[
[
[
10] a) K. C. Nicolaou, W.-M. Dai, R. K. Guy, Angew. Chem. Int. Ed. Engl. 1994,
33, 15–44; Angew. Chem. 1994, 106, 38–69; b) K. C. Nicolaou, R. K. Guy,
Angew. Chem. Int. Ed. Engl. 1995, 34, 2079–2090; Angew. Chem. 1995,
1
07, 2247–2259.
11] a) T. Nakata, Chem. Rev. 2005, 105, 4314–4347; b) M. Inoue, Chem. Rev.
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01–426; d) K. C. Nicolaou, M. O. Frederick, R. J. Aversa, Angew. Chem.
2
4
Int. Ed. 2008, 47, 7182–7225; Angew. Chem. 2008, 120, 7292–7335.
12] a) P. A. Evans, B. Holmes, Tetrahedron 1991, 47, 9131–9166; b) G. Illumi-
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Keywords: annulation · carbenes · heterocycles · rhodium ·
ring expansion
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[
Manuscript received: May 13, 2015
Accepted Article published: August 6, 2015
Final Article published: September 14, 2015
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Chem. Asian J. 2015, 10, 2624 – 2630
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