A new preparation of cis-N-sulfonylaziridines from N-sulfonylaldimines using trimethylsilyldiazomethane

Article abstract of DOI:10.1016/S0040-4039(00)01601-4

Trimethylsilyldiazomethane smoothly reacts with N-sulfonylaldimines to give 2-substituted N-sulfonyl-3-trimethylsilylaziridines in good yields with high cis selectivity. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)01601-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 9455–9458
A new preparation of cis-N-sulfonylaziridines from
N-sulfonylaldimines using trimethylsilyldiazomethane†
Rina Hori, Toyohiko Aoyama* and Takayuki Shioiri*
Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan
Received 26 July 2000; revised 13 September 2000; accepted 14 September 2000
Abstract
Trimethylsilyldiazomethane smoothly reacts with N-sulfonylaldimines to give 2-substituted N-sulfonyl-
3-trimethylsilylaziridines in good yields with high cis selectivity. © 2000 Elsevier Science Ltd. All rights
reserved.
Keywords: trimethylsilyldiazomethane; N-sulfonylaldimine; N-sulfonylaziridine.
Aziridines are useful building blocks in organic synthesis, and a variety of methods for the
preparation of aziridines have been reported.1 However, the most attractive approach is either
1,2-addition of carbon to a carbonꢀnitrogen double bond2 and 1,2-addition of nitrogen to a
carbonꢀcarbon double bond.3
We have already demonstrated that trimethylsilyldiazomethane (TMSCHN2) is very useful as
a reagent for the introduction of a C-1 unit.4 For instance, TMSCHN2 smoothly reacts with
electron-deficient olefins such as tetracyanoethylene and benzylidenecyanoacetate to give silylcy-
clopropanes.5 Our continued interest in the use of TMSCHN2 as a C-1 unit introducer has led
us to investigate the aziridination of N-sulfonylaldimines, electron-deficient imines, with
TMSCHN2. During the course of our work, two examples of the Lewis acid-catalyzed
aziridination of a-imino esters using TMSCHN2 were reported.6
We have found that TMSCHN2 smoothly reacts with N-sulfonylaldimines (1) in refluxing
toluene to give 2-substituted N-sulfonyl-3-trimethylsilylaziridines (2) in good yields with high cis
selectivity.7 In many cases, small amounts of C-methylated N-sulfonylimines (3) were formed as
byproducts (Scheme 1).
* Corresponding authors. Fax: +81-52-834-4172; e-mail: shioiri@phar.nagoya-cu.ac.jp
†
Dedicated to Professor Harry Wasserman on the occasion of his 80th birthday.
0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)01601-4

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Scheme 1.
A typical experimental procedure is as follows (entry 4 in Table 1): A mixture of 1d8 (144 mg,
0.5 mmol) and TMSCHN2 (1.67 M in hexane, 0.45 ml, 0.75 mmol) in dry toluene (5 ml) was
stirred at reflux for 7 h. After removal of the solvent in vacuo, the residue was purified by
column chromatography on silica gel (EtOAc:hexane=1:6) to give 2d (159 mg, 85%) and 3d (15
mg, 10%).
The results are summarized in Table 1. The sulfonyl moiety of the imines 1 affected both the
yield and the stereoselectivity (entries 1–5). Among those examined, the mesitylenesulfonyl
group as a substituent gave the best result (entry 4). Various mesitylenesulfonylaldimines (1f–n)
Table 1
Preparation of cis-N-sulfonylaziridines 2a
Entry
Compound no.
R1 time (h)
R2
Reaction
Yield (%)b
2
3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p-MeC6H4
p-NO2C6H4
p-MeOC6H4
2,4,6-Me3C6H2
Benzyl
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
(1R)-10-Camphor
Phc
3
1
4.5
7
1
5
5
24
9
2
2
75 (cis only)
10
18
10
10
–
Phc
45 (cis/trans=91/6)d
80 (cis/trans=94/6)d
85 (cis only)
Phc
Phe
Phc
65 (cis/trans=87/13)d
81 (cis only)
78 (cis only)
(9)d
12
e
p-ClC6H4
p-NO2C6H4
e
(10)d
(10)d
–
–
–
30
20
–
e
p-MeOC6H4
2-Naphthyle
2-Furyle
76 (cis only)
76 (cis only)
82f (cis only)
59 (cis only)
3-Pyridyle
Styryle
2
1
1
4
12 (cis only)
60 (cis only)
65 (cis only)
88 (cis only)
Phenethyle
n-Pentyle
Phc
(de=0%)
a All new compounds gave satisfactory spectral data and elemental analysis (or HRMS data).
b Isolated yield.
c TMSCHN2 (1.2 equiv.) was used.
1
d Determined by H NMR.
e TMSCHN2 (1.5 equiv.) was used.
f The compound 2j was very unstable under column chromatography conditions, so it was isolated by recrystalliza-
tion (hexane).

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derived from aromatic, heteroaromatic, and aliphatic aldehydes smoothly underwent the reac-
tion with TMSCHN2 to give the cis-aziridines (2f–n) in high to moderate yields (entries 4, 6–14).
Although (1R)-10-camphorsulfonylaldimine (1o) also gave the cis-aziridine (2o) in high yield, no
diastereoselectivity was observed.
The trimethylsilyl group of 2 can be easily removed with tetrabutylammonium fluoride
(TBAF) to give the 2-substituted N-sulfonylaziridines.9
Furthermore, the reaction of the N-sulfonylketimine (3a) with TMSCHN2 also proceeded to
give the aziridine 4, but a very long reaction time (30 h) was required and yet the yield was low10
(Scheme 2).
Scheme 2.
In contrast to the Jørgensen’s aziridination6 in which significant quantities of the trans isomers
were produced by the Lewis acid catalyzed reaction, the exclusive formation of the cis isomers
was observed without use of Lewis acids in our case.
The high cis-selectivity of the reaction could be explained by steric hindrance between the
trimethylsilyl and the bulkier arylsulfonyl groups in the first formed betain intermediates A and
B, in which the latter would lead to a minimum steric hindrance and afford the cis-aziridine with
expulsion of nitrogen after rotation to the intermediate C (Scheme 3).
Scheme 3.
In conclusion, compared to the Lewis acid-catalyzed aziridination of a-imino esters using
TMSCHN2,6 the present method makes possible the simple, high-yield, and high stereoselective
conversion of N-sulfonylaldimines to cis-N-sulfonylaziridines, and will provide an added
flexibility in the aziridine synthesis.

9458
Acknowledgements
This work was partially supported by Grant-in-Aid from the Ministry of Education, Science,
Sports and Culture, Japan.
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