Cyclic and acyclic sulfonimides in reactions with Rh(II)-ketocarbenoids: A new access to chemoselective O-functionalization of the imidic carbonyl groups

Article abstract of DOI:10.1039/b508317f

Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and ¹H- and ¹³C-NMR studies it was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution. Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b508317f

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A R T I C L E
Cyclic and acyclic sulfonimides in reactions with
Rh(II)-ketocarbenoids: a new access to chemoselective
O-functionalization of the imidic carbonyl groups†‡
Vsevolod Nikolaev,a Lothar Hennig,b Jochim Sieler,b Ludmila Rodina,a Barbel Schulze*b and
Valerij Nikolaev*a
a Saint-Petersburg State University, University prosp. 26, Saint-Petersburg, 198504, Russia.
E-mail: vnikola@VN6646.spb.edu; Fax: 7 812 4286939
b Universita¨t Leipzig, Institut fu¨r Organische Chemie, Johannisallee 29, 04103 Leipzig,
Germany. E-mail: bschulze@organik.chemie.uni-leipzig.de
Received 14th June 2005, Accepted 26th August 2005
First published as an Advance Article on the web 3rd October 2005
Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic
esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of
N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the
imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction
proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields
of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and 1H- and 13C-NMR studies it
was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution.
Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular
cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process.
will primarily react with the nitrogen atom of an imidic system,
Introduction
giving rise to N-alkylated sulfonimides as usually occur in
Insertion reactions of metal-stabilized carbenes (carbenoids)
reactions of electrophiles with saccharins.7 Basically, a similar
into X–H bonds of different compounds (X = C, N, O, S, etc.)
tendency is observed in the previously described reactions of
has become a recent standard procedure in organic synthesis.1,2
amides and lactams with a variety of carbenoids,3–5,9 although
A special area in this field occupies the insertion of carbenoids
in catalytic reactions of diazoacetic esters a few examples of
B into N–H bonds of amides, lactams and similar structures A
O-alkylation of the amide carbonyl group also exist.10
(Scheme 1), which took on great popularity after the elaboration
According to our previous results11 we now report the
of a general approach for the synthesis of bicyclic b-lactams on
Rh(II)-catalyzed decomposition of diazocarbonyl compounds
in the presence of isothiazol-3(2H)-one 1,1-dioxides 1 and N-
(arenesulfonyl)carboxamides 2.
the basis of this transformation.3 Since then, the high efficiency
of carbenoid N–H insertion was repeatedly demonstrated in the
synthesis of a wide variety of N-containing structures C.4,5
Results and discussion
Chemical product studies of Rh(II)-catalyzed reactions
Four cyclic sulfonimides were used in this research: 1,2-
benzisothiazol-3(2H)-one 1,1-dioxide (saccharin) 1a; two hydro-
Scheme 1 Ordinary direction of Rh(II)-ketocarbenoid reactions with
amides, lactams and associated systems containing the CO–NH-moiety
in the molecule.
genated analogues 4,5,6,7-tetrahydro-1,2-benzisothiazol-3(2H)-
one and 5,6,7,8-tetrahydro-4H-cyclohepta[d]isothiazol-3(2H)-
one 1,1-dioxides 1b,c respectively; and the monocyclic 5-methyl-
4-phenyl-isothiazol-3(2H)-one 1,1-dioxide 1d (Scheme 2).
In the context of our research in the chemistry of
isothiazol-3(2H)-one 1,1-dioxides and their reactions with diazo
compounds6 we undertook an attempt to realize the insertion
reaction of ketocarbenoids into the N–H bond of these 5-
membered cyclic imides as well as of their acyclic analogues,
N-(arenesulfonyl)carboxamides. The primary goal of the pre-
sented study was to develop a new strategy for the synthesis
of the potentially biologically active N-alkyl-functionalized
sulfonimides.7,8
Sulfonimides possess a few nucleophilic groups that can
serve as potential centres for interaction with metal-stabilized
carbenes, exhibiting a pronounced electrophilic reactivity.1,2
Nevertheless, one might expect that an electrophilic carbenoid
† Electronic supplementary information (ESI) available: X-ray crys-
tal structures of compounds 4c and 5b. See http://dx.doi.org/
10.1039/b508317f
‡ Dedicated to Professor Manfred Regitz on the occasion of his 70th
birthday.
Scheme 2 Isothiazole 1,1-dioxides 1, acyclic sulfonimides 2 and
diazocarbonyl compounds 3 for Rh(II)-catalyzed reactions.
4 1 0 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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Among the acyclic imidic substrates for our investigation were
selected N-(arenesulfonyl)carboxamides 2a–c, with different
natures of the acyl substituents (COMe, COPh) on the imidic N
atom and para-substituents (Me, Cl) on the aryl ring.
Diketocarbenoids were generated from three different types
of diazocompounds: diazomalonic 3a and diazoacetoacetic 3b
esters; diazoacetylacetone 3c; and, for comparison, also from
diazoacetic ester 3d, which is stabilized with only one carbonyl
group (Scheme 2). Catalytic decomposition of diazocompounds
was performed by the addition of 1–2 mol% of dirhodium
tetraacetate at 15–20, 45 or 80–83 ◦C in dry dichloromethane or
dichloroethane. Upon completion of the reaction as indicated
by TLC, the reaction mixture was separated on the column with
neutral silica gel.
At the same time during the catalytic decomposition of diazo-
compounds 3a,c,d in the presence of sulfonimide 2c bearing the
N-aroyl substituent, after work-up of the reaction mixture only
the initial sulfonimide 2c (80–87%) was isolated, although from
the 1H NMR data immediately upon completion of the catalytic
process significant amounts (>35–40%) of the corresponding
imidates 5i,j were detected in the reaction mixture (Table 1).
Variation of the reaction and experimental conditions (using
reduced temperature, separation of reaction mixture without
silica gel, etc.) did not give a positive result, evidently due to
the easy hydrolysis of O-alkylimidates 5i,j during the work-
up procedure, and we did not manage to isolate them in pure
form.
To summarize, it can be concluded that the above trans-
formation of cyclic and acyclic sulfonimides 1 and 2 offers a
new O-alkylation reaction of imidic carbonyl groups by metal-
carbenes and enables a one-stage synthesis of O-alkylimidates
with a polyfunctional framework in the molecule.
As could be expected, as a consequence of the catalytic
decomposition of diazocompounds 3a–d by Rh2(OAc)4 in the
presence of sulfonimides 1a–c and 2a,b the adducts of the imidic
substrates and the corresponding ketocarbenes in the ratio of 1 :
1 were isolated. Spectroscopic investigations, however, revealed
that the compounds obtained did not have the structure of the
assumed N-alkylated products. It turned out that they comprised
O-alkylimidates 4 and 5, that is, the formal insertion products of
the corresponding ketocarbenes into the O–H bond of the enol
form of imides 1 and 2 (Table 1). Reaction generally proceeded
with a good preparative yield (up to 90–95%) and by the data
Spectroscopic investigations and structure of O-
alkylimidates 4, 5
Owing to the lack of literature data regarding the spectroscopic
properties of the O-alkylation products of imides by ketocar-
1
benoids, a detailed study of imidates 4 and 5 using H- and
1
13C-NMR spectroscopy was undertaken . The aim of this part
of our research was to elucidate the characteristic parameters of
O-alkylimidates 4 and 5 and the possibility of their subsequent
of H NMR spectroscopy of the ‘crude’ reaction mixture the
occurrence of isomeric N-alkyl derivatives 6 of imides under
these conditions was not observed.
Table 1 O-Alkylation of isothiazol-3(2H)-one 1,1-dioxides 1 and acyclic sulfonamides 2 via Rh(II)-ketocarbenoids 3ꢀ from diazocarbonyl
compounds 3a
Imidate
R–R1
R2, R3
Yield (%)b
90
Imidate
R
R1
R2, R3
Yield (%)b
90
4a
CO2Me, CO2Me
5a
Me
Tol
CO2Me, CO2Me
4b
4c
4d
4e
COMe, CO2Et
COMe, COMe
H, CO2Et
76
5b
5c
5d
5e
Me
Me
Me
Me
p-ClC6H4
Tol
CO2Me, CO2Me
COMe, CO2Et
COMe, CO2Et
COMe, COMe
87
78
68
77
8611
80
p-ClC6H4
Tol
CO2Et, CO2Etc
9511
4f
COMe, COMec
CO2Et, CO2Et
8611
8111
5f
Me
p-ClC6H4
COMe, COMe
47
4g
5g
5h
5i
Me
Me
Ph
Tol
p-ClC6H4
Tol
H, CO2Et
H, CO2Et
CO2Me, CO2Me
COMe, COMe
41
28
>40d
>35d
5j
Ph
Tol
a For detailed reaction conditions see the Experimental section. b Isolated yield after flash chromatography. c Compound 4e, n = 1; 4f, n = 2. d From
the data of 1H NMR spectra.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6
4 1 0 9

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Table 2 13C NMR spectra of imidates 4a–g, 5a,b,g,h and N-alkyl derivatives 6a–c in 0.2–0.3 mol solutions of CDCl3
Compounds 4, 5, 6
Entry No. R2, R3
Signals of carbon atoms, d/ppma
=
=
O–CH or
N–CH
N
C–O or AlkO–C O or
=
O
=
N–C
Me–C
O
Other C atoms
1
2
4a
CO2Me, CO2Me
76.0
76.3
168.2
170.6
163.1
162.9
53.9 (OCH3), 122.2, 124.0, 125.5, 133.8, 134.7, 143.7 (C-arom.)
14.1 (CH3), 20.4, 20.79, 20.84, 21.0 (CH2), 63.3 (OCH2), 131.9
(4-C), 155.2 (5-C)
14.3 (CH3), 63.6 (OCH2), 126.5, 129.1, 129.2, 130.0 (C-arom.), 130.6
(4-C), 152.8 (5-C)
4eb CO2Et, CO2Et
4gb CO2Et, CO2Et
3
4
77.1
74.6
170.8
168.3
162.9
164.3
164.1
=
5a
CO2Me, CO2Me
20.0 (CH3Ar), 21.9 (CH3C N), 53.7 (OCH3), 127.2, 129.8, 138.3,
144.2 (C-arom.)
=
5
6
5b
4b
CO2Me, CO2Me
COMe, CO2Et
74.7
82.3
172.3
168. 2
20.2 (CH3C N), 53.7 (OCH3), 128.6, 129.5, 139.7, 139.8 (C-arom.)
14.1(CH3CH2), 27.5 (CH3CO), 63.3(CH3CH2), 122.2, 123.9, 125.7,
133.8, 134.8, 143.7 (C-arom.)
194.9, 162.7
7
8
4cb COMe, COMe
4fb COMe, COMe
89.8
90.0
168.3
170.9
197.0
196.8
27.8 (CH3CO), 122.7, 123.9, 126.0, 134.2, 135.2, 144.1 (C-arom.)
25.0, 25.5, 26.6, 26.8, 29.5 (CH2), 27.6 (CH3CO), 132.8 (4-C), 157.3
(5-C)
9
4d
5g
5h
H, CO2Et
H, CO2Et
H, CO2Et
66.1
63.8
63.1
168.9
172.6
172.2
165.6
166.5
165.4
13.8 (CH3CH2O), 61.9 (CH3CH2O), 121.7, 123.5, 125.7, 133.6,
134.4, 143.2 (C-arom.)
=
10
11
13.8 (CH3CH2), 19.6 (CH3C N), 21.4 (CH3Ar), 61.3 (CH3CH2),
126.6, 129.3, 138.3, 143.4 (C-arom.)
=
12.9 (CH3CH2), 19.0 (CH3C N), 60.5 (CH3CH2), 127.2, 128.0,
138.1, 138.7 (C-arom.)
12
13
6a
6b
CO2Me, CO2Me
H, CO2Et
54.7
39.1
168.2
165.9
158.6
158.7
54.2 (OCH3), 121.7, 126.1, 127.0, 135.1, 135.8, 137.9 (C arom.)
14.0 (CH3CH2), 62.2 (CH3CH2), 121.2, 125.4, 126.9, 134.5, 135.2,
137.6 (C-arom.)
14
6c
H, COCH2CO2Et 46.6
166.1
158.8
14.0 (CH3CH2), 46.54 (COCH2CO), 61.8 (OCH2), 121.2, 125.3,
126.8, 134.6, 135.2, 137.6 (C-arom.), 193.6 (NCH2CO)
a
=
=
=
=
For the sake of convenience the data for O–CH, N C–O, N–C O, N–CH, AlkO–C O and Me–C O groups are placed in the three first carbon
signal columns of the table. b Data from the preliminary publication.11
use for the identification of similar compounds by spectroscopic
methods. Some of these results are considered below (Table 2);
other data are given in the Experimental section.
of the O–CH group at 5.4–5.5 ppm or of the O–CH2 group at
4.5–4.6 ppm were observed. Therefore, one can conclude that
the O-alkylimidates 5 in solution at ordinary temperatures most
likely persist as a single stereoisomer. In the 1H NMR spectrum
of the ‘crude’ reaction mixture of imidate 5i from sulfonimide
In the 1H NMR spectra sharp singlet signals of methine
(OCHR2R3; 5.4–5.9 ppm) or methylene group (OCH2CO2Et;
4.5–5.0 ppm) were observed. In the carbon spectra strong signals
of the same fragments (OCHR2R3 and OCH2CO2Et) appear
at 75–90 and 63–66 ppm, respectively. The signal shift of the
methine carbon atom strongly depends upon the substituents R2.
With two acyl substituents the corresponding atom was found
around 90 ppm (4c,f). Replacement of one of them with an
alkoxycarbonyl group causes a high-field shift to 82 ppm (4b).
Incorporation of one more alkoxycarbonyl group (4a,e,g) results
in further shifting of the OCH signal to stronger field and was
hence found at 76–77 ppm.
=
2c with the more bulky phenyl group at the C atom of the C N
bond two separate signals were found (at 5.61 and 5.73 ppm).
It seems likely that in solution two stereoisomers of imidate
5i are present, but we were not able to isolate them as pure
products.
It also should be noted that compounds 4b,c,f and 5c–f with
an acetyl group in 1,3-dicarbonyl fragment of the molecule are
not enolized in solution and in the solid state, according to
NMR and IR spectroscopy. This is contrary to similar N-alkyl
derivatives from amides and lactams which exist solely in the
enol form.9a,15 This finding greatly simplifies the spectroscopic
identification of O-alkylated sulfonimides.
The structures of 4 and 5 were also confirmed by X-ray
structure determination with adducts 4c and 5b, derivatives
of the cyclic 1 and acyclic 2 imides correspondingly, whose
geometry is presented in Fig. S1 and S2 (see ESI†). These
data unambiguously ascertained the structure of the resultant
compounds 4 and 5 as O-alkyl derivatives of the sulfon-
imides. On this basis it is also evident that O-alkylimidates
5 of acyclic sulfonimides have the E-configuration, and both
O-alkylimidates 4 and 5 have the s-cis conformation with regard
to the C(7)–O(3)CHR2R3 bond.
The signals of the proton and carbon atoms of the O–CH
fragment in the NMR spectra of acyclic O-alkylimidates 5a,b
are typically observed in the same regions (5.4–5.5 and 74.6–
74.7 ppm) which were found for their analogues 4a,e,g in the
series of saccharins (5.7–5.9 and 76.0–77.1 ppm; Table 2).
Acyclic imidates 5 can exist as Z- and E-stereoisomers E-
5 and Z-5. According to the literature data,12 O-alkylimidates
=
with small substituents (Me, Et, etc.) at the C N bond normally
have the E-configuration, but with bulky substituents (t-Bu, Ph
and others) on the carbon and nitrogen atoms of this bond, the
Z-stereoisomer also appears in equilibrium.13 In specific cases,
the E- and Z-isomers of the imidates can be separated using
flash chromatography or recrystallization of the stereoisomeric
mixture.12,14
N-Alkylation of sulfonimides 1 and 2 using alkyl halides
To produce isomeric N-alkyl derivatives 6 and by this means to
obtain indirect corroboration of the structure of O-alkylimidates
4 and 5 by chemical methods, a few reactions of sulfonimides 1
and 2 with electrophilic alkyl halides, namely – with bromo-
malonic, bromoacetoacetic and chloroacetic esters were also
studied. Reactions were carried out with sodium and potassium
salts of the imides 1a and 2a in solutions of dry DMF or THF.16
In the proton spectra of imidates 5a–h, bearing a methyl group
on the C atom of the C N bond, only one signal for the protons
=
4 1 1 0
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6

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Reaction of the sodium salt of saccharin 1a with the
above-mentioned alkyl halides in DMF solution produced the
relevant N-alkyl-substituted saccharins 6a–c (Scheme 3). For
advantageous preparation of N-bis(alkoxycarbonyl)methylene
derivatives 6a from the sodium salt of saccharin 1a-Na and
the corresponding bromomalonates it was necessary to carry
out the reactions at a temperature of about 70 ◦C. Increasing
the temperature to 100–120 ◦C in the reaction with ethyl
bromomalonate resulted in the sole formation of N-substituted
saccharin 6b, probably due to the easy hydrolysis followed by
decarboxylation of one of the ester groups of the initially-formed
derivative of malonic acid 6a (R3 = CO2Et) at temperatures
above 100 ◦C.16b
transfer either via a [1,4]-sigmatropic hydrogen shift10c,d or by
H-migration to the anionic centre of the carbonyl ylide through
intermediate E.
Formation of the O–H insertion products 4, 5, by the
‘oxonium’ pathway involving the enol form of sulfonimides 1, 2
and then oxonium ylides, seems unlikely.11
Attempts to obtain experimental support in favour of
the intermediate occurrence of carbonyl ylides D with the
help of their cycloaddition to dimethyl acetylenedicarboxylate
(DMAD)2b,17,18 using sulfonimides 1, 2 with an unsubstituted
N–H group have been unsuccessful. Catalytic decomposition of
diazomalonic ester 3a in the presence of imides 1a or 2a with an
excess of DMAD results in the formation of O-alkylimidates 4a
or 5a.
These data clearly indicate that the stabilization of carbonyl
ylide D via an intramolecular [1,4]-H-shift occurs more rapidly
than its intermolecular reaction with DMAD. Therefore, cy-
cloadducts of the carbonyl ylide and DMAD should be expected
using N-substituted sulfonimides with no possibility for H-
migration. However, similar catalytic reaction of diazomalonic
ester 3a with N-methyl- or N-phenyl-substituted saccharins 1e,f
in the presence of DMAD also failed to produce cycloadducts.
In both cases only the initial N–Me- and N–Ph-isothiazoles 1e,f
were found in the reaction mixture, together with significant
quantities of the bis(methoxycarbonyl)carbene ‘dimer’ (identi-
fied by NMR spectra).
Scheme 3 N-Alkylation of isothiazole 1,1-dioxide 1a using alkyl
halides.
In order to explain the reasons behind the unsuccessful
Positive results were not achieved in the experiments with
the acyclic sulfonimides 2a,b or their potassium and sodium
salts under the same conditions; also, substitution of DMF for
tetrahydrofuran16c in alkylation reactions of the sodium salt 1a-
Na with alkyl halides also failed.
As evident from spectral data of the N-substituted imides
6a–c, the major difference in the proton and carbon spectra of
isomeric O- and N-alkyl derivatives 4 and 6 is exhibited in the
location of the signals for H and C atoms of the methine and
methylene groups (O–CH, N–CH and O–CH2, N–CH2) (see
Table 2 and the Experimental section). The proton signals of
these groups shift to stronger field by 0.6–0.7 ppm upon moving
from O-alkylimidates 4a,d to the corresponding N-alkylation
products 6a and 6b, while the signals of the C atoms of the
same groups move to stronger field by 21–24 ppm. Pronounced
distinctions (4.5–6.5 ppm) are also found in the location of the
=
attempts of adding ‘intermolecular’ C O-ylides D from N-
substituted saccharins 1e,f to DMAD, the reactivity of their
assumed ‘intramolecular’ analogue – carbonyl ylide D1 – was
examined under the same conditions. For this purpose, N-alkyl-
substituted oxoisothiazole 1,1-dioxide 7 was prepared with the
diazocarbonyl moiety directly in the structure of the starting
substrate and without the ‘free’ hydrogen at the imidic nitrogen
atom (Scheme 5).
=
=
imidate and carbonyl carbon atoms (N C–O and N–C O) of
the sulfonimidic derivatives 4 and 6.
These correlations clearly demonstrate the essential differ-
ences in the proton and carbon NMR spectra of N- and O-
alkyl-substituted sulfonimides 4 and 6, and allow us to make
conclusive structural assignments based on these data.
Trapping of intermediate carbonyl ylide and likely pathway of
the reaction
Scheme 5 Synthesis and catalytic decomposition of diazosaccharin
7 in the presence of DMAD. Reagents and conditions: a) BrCH2COCH2-
CO2Et, DMF, 90 ◦C, 46%; b) p-acetamidobenzenesulfonyl azide
(ABSA), Et3N, CH2Cl2, 20 ◦C, 84%; c) Rh2(OAc)4, DMAD, CH2Cl2,
12 h, 61%.
The mechanism of formation of the O-alkyl imidates 4 and
5 apparently involves intermediate generation of the car-
bonyl ylide D due to initial attack of the electrophilic keto-
carbenoid 3ꢀ on the carbonyl oxygen atom (Scheme 4).2a,b,10,17,18
The succeeding stabilization of ylide D into O-alkyl imidates
4 and 5 may occur by intramolecular NH group hydrogen
The catalytic decomposition of this diazosaccharin 7 in
the presence of an 8-fold excess of DMAD resulted in the
formation of the relevant cycloadduct 8 of the intermediate
‘intermolecular’ carbonyl ylide D1 with dipolarophile (DMAD)
in good yield (ca. 60%).
The essential discrepancy in reactivity of the ‘intermolecular’
D and ‘intramolecular’ D1 carbonyl ylides could be explained in
the following manner. Owing to the presence of the substituent
(Me or Ph) at the imidic N atom in the molecule of carbonyl
ylide D, two bulky groups (CO2Alk, COMe) of the carbene
fragment are apparently positioned orthogonally to the plane of
the dipole C+–O–C− and thereby cause severe steric hindrance
Scheme 4 Carbonyl ylide pathway for O-alkylation of sulfonimides 1,
2 via ketocarbenoids 3ꢀ.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6
4 1 1 1

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for the approach of the dipolarophile to the reacting orbitals of
the reaction conditions; also, as the final products of this process,
N-derivatives C are produced.
=
this ‘intermolecular’ C O ylide (Scheme 6).
For O-alkylimidates 4, 5 (route ‘b’), a similar rearrange-
ment can be presumably hindered in view of the bulky and
strongly electronegative SO2 group adjacent to the end point of
migration. This group can strongly reduce the electrophilicity of
the a-N-atom and in addition prevent migration of the bulky O-
substituent to the nitrogen atom because of steric reasons. It is
apparently this reason that gives the opportunity for isolation of
the initial O-alkylation derivatives of sulfonimides from reaction
mixture.
Scheme 6 Different stereochemistries of ‘inter-’ and ‘intra-molecular’
carbonyl ylides D and D1.
Conclusion
By contrast, all four substituents at the dipole’s C atoms
are actually located in the plane of the 1,3-dipole itself in the
dipolar structure of the ‘intramolecular’ carbonyl ylide D1. As
a consequence of these changes, the steric problems for the
approach of DMAD to the reactive centers of ylide D1 are clearly
removed and cycloaddition between these moieties can proceed
more effectively.
Thus, the main line of interaction of Rh(II)-ketocarbenoids
with cyclic and acyclic sulfonimides is the initial attack on the
oxygen atom of the carbonyl group, with intermediate formation
of the carbonyl ylide that ultimately leads to O-alkylation
of these imidic substrates. As has already been mentioned
above, essentially only N-alkylation products of the starting
compounds were isolated in similar reactions of amides, lactams
and related structures with a variety of ketocarbenoids.3–5,9,15
The reason for such a drastic difference in the ketocarbenoid’s
reactivity with amides, lactams and sulfonimides 1 and 2 (as
investigated by us) is still not understood.
We have shown that: (a) rhodium-catalysed decomposition
of diazocarbonyl compounds in the presence of saccharins
and N-(arenesulfonyl)acetamides is a powerful tool for the O-
functionalization of their carbonyl groups by reaction with
the transient ketocarbenoids; and (b) the discovered reaction
is a highly chemoselective process, which provides a new and
effective approach for the structure of O-alkylimidates from
oxoisothiazole 1,1-dioxides and N-(arenesulfonyl)acetamides.
The reasons for the dissimilar chemical behaviour of amides,
lactams and sulfonimides in reactions with metal-stabilized
carbenes are as yet unclear, and this is a subject of current
investigation in our laboratories.
Experimental
General notes
1H and 13C NMR spectra were measured on VARIAN ‘Gemini
200’, ‘Gemini 300’ and BRUKER DRX-600 ‘AVANCE’ spec-
trometers, at working frequencies of 200, 300, and 600 MHz
=
The amidic moiety (O C–NH) of isothiazol-3(2H)-one
1,1-dioxides 1 and acyclic sulfonimides 2 is a typical am-
bident system,7a,19 capable of interacting with electrophilic
reagents at the nitrogen or/and oxygen atoms of this group.
In view of the amide character of their structure the N-
substituted sulfonimides should be thermodynamically more
stable than the isomeric O-substituted derivatives related to
the imidate structure.7a,20 This conclusion is corroborated by
numerous examples of irreversible thermal isomerisation of O-
alkyl(aryl)imidates into their associated N-derivatives,7a,16c,21–23
known as the Lander–Chapman rearrangement.12,21 The trend
toward oxygen-to-nitrogen rearrangement increases substan-
tially with multiple bonds and electron accepting groups in the
migrating fragment of the imidate.7a And in the presence of
a specific catalyst this rearrangement can take place even at
moderate temperatures,23 i.e. catalytic reaction can proceed by-
passing the stage of isolable O-alkyl derivatives.
1
for H NMR and 50.3, 75.45 and 150.92 MHz for 13C NMR
spectra; solutions were in CDCl3 or DMSO-d6, internal standard
Me4Si (d, ppm), J values are given in Hz. Infrared spectra were
obtained using an ATI Mattson ‘Genesis Series FTIR’ or with
a Specord IR-75 instrument. Mass spectra were determined by
electron impact at 70 eV on a Quadrupol-MS VG 12–250 (VG
Instruments GmbH, Manchester Analytical). Microanalysis
was performed on an Heraeus CHNS Rapid Analyser. Melting
points were determined on a Boetius micro melting point
apparatus and were uncorrected.
All reactions were carried out in carefully dried and dis-
tilled solvents. Rhodium(II) acetate and saccharin 1a were
commercially available (Fluka). Other 3-oxoisothiazoles 1
and sulfonimides 2 were prepared according to the previous
publications24,25 and for extra purification they were sublimated
in vacuo at 30–50 ◦C/0.05 mm Hg. Diazodicarbonyl compounds
3a–c were prepared from the corresponding 1,3-dicarbonyl
compounds and arenesulfonyl azides using a diazotransfer
reaction1,26 followed by distillation in vacuo. Commercially
available diazoacetic ester 3d (Fluka) was distilled just before
carrying out the catalytic reaction, bp 58–60 ◦C/1 mm Hg.
Reactions were monitored by thin-layer chromatography
(TLC) on Silufol UV/VIS plates using 254 nm UV light
and J2 as the visualizing agents. Neutral silica gel (MERCK
70–230 mesh or CHEMAPOL L 40/100) was used for column
chromatography.
Based on the aforesaid it may be suggested that initially in
the course of amide and lactam reactions with ketocarbenoids,
O-alkylation products F are generated (Scheme 7, route ‘a’) as
in the case of sulfonimides 1, 2 which then experience oxygen-
to-nitrogen rearrangement of the diketocarbene fragment under
General procedure for catalytic decomposition of diazomalonates
3a, diazoacetoacetic esters 3b and diazoacetylacetone 3c in the
presence of sulfonimides 1, 2 to produce O-alkylimidates 4a,b
and 5a–f
To a solution or suspension of sulfonimides 1, 2 (2.0 mmol)
and diazocompound 3a–c (2.3 mmol) in 5–15 mL in methylene
chloride or dichloroethane at 18–20 ◦C was added in one
portion 5–10 mg (11–23 lmol) of dirhodium tetraacetate and
Scheme 7 Assumed ways of carbenoid reaction with amides, lactams
(a) and sulfonimides (a).
4 1 1 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6

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the mixture was stirred to completion of the decomposition
of the diazocompound (3–24 h in the case of diazomalonates 3a,
and 20–40 min for the decomposition of the diazocompounds
3b,c; control using TLC). The solvent was removed in vacuo
to a volume of 2–3 mL and the residue was filtered through
a small layer of neutral silica gel (eluent mixture of CH2Cl2–
Et2O = 1 : 1 to 1 : 2). The isolated compounds were analyzed
by means of spectroscopic methods and, if need be for addi-
tional purification, they were crystallized from the appropriate
solvents.
(Acetylethoxycarbonyl)methyl ester of N-(4-chlorobenzene-
sulfonyl)imidoylacetic acid 5d. Yield 0.49 g (68%), oily com-
pound, Rf = 0.27 (hexane–Et2O 1 : 1); dH(300 MHz, CDCl3,
=
Me4Si) 1.17 (3H, t, J 7.4, CH2CH3), 2.21 (3H, s, CH3C O),
=
2.61 (3H, s, N CCH3), 4.11 (2H, q, J 7.4, CH2CH3), 5.38 (1H, s,
OCH), 7.46 (2H, d, J 9.0, H-arom.), 7.76 (2H, d, J 9.0, H-arom.);
m/z (EI) 361 (M+ 3.5%), 345 (7.1), 319 (16.4), 296 (7.8), 278
(40.3), 274 (20.2), 211 (77.0), 183 (61.1), 175 (19.7), 171 (22.2),
156 (19.4), 129 (36.1), 111 (25.0), 103 (16.6), 83 (99.3), 67 (66.6),
55 (42.7), 43 (100.0).
After complete decomposition of the diazoacetoacetic ester
3b and diazoacetylacetone 3c in the presence of N-(4-Cl-
benzenesulfonyl)acetamide 2b and concentration of the resul-
tant mixture to a volume of 3–4 mL, the unreacted imide 2b
was separated by filtration and the mother liquid was treated
analogously to general procedure.
(Diacetyl)methyl ester of N-(4-methylbenzenesulfonyl)-
imidoylacetic acid 5e. Yield 0.48g (77%), oily compound, Rf =
0.23 (hexane–Et2O 2 : 1); dH(300 MHz, CDCl3, Me4Si) 2.14
=
(6H, s, 2 COCH3), 2.38 (3H, s, CH3Ar), 2.59 (3H, s, N CCH3),
5.40 (1H, s, OCH), 7.28 (2H, d, J 8.0, H-arom.), 7.67 (2H, d,
J 8.0, H-arom.); m/z (EI) 311 (M+, 1.0%), 279 (1.2), 285 (1.2),
270 (16.0), 243 (7.2), 227 (15.2), 214 (15.3), 197 (6.24), 187 (8.3),
173 (12.6), 155 (20.0), 114 (19.5), 108 (13.0), 91 (69.5), 72 (32.0),
65 (26.5), 43 (100.0).
3-(Dimethoxycarbonyl)methoxy-1,2-benzisothiazole 1,1-
dioxide 4a. Yield 0.56g (90%), colorless crystals, Rf = 0.18
(hexane–Et2O 1 : 1), mp 116–117 ◦C (from CH2Cl2–hexane)
(Found: C, 46.2; H, 3.7; N, 4.3. Calc. for C12H11NO7S: C, 46.0;
H, 3.5; N, 4.5%); mmax(KBr)/cm−1 2997s, 2308vs, 1757m, 1337m,
1160m; dH (300 MHz, CDCl3, Me4Si) 3.92 (6H, s, 2OCH3), 5.96
(1H, s, OCH), 7.73–7.93 (4H, m, H-arom.); m/z (EI) 313 (M+,
7.5%), 282 (15.3), 269 (7.5), 249 (27.8), 212 (27.5), 198 (50.4),
166 (35.6), 150 (10.9), 117 (50.8), 102 (100.0).
(Diacetyl)methyl ester of N-(4-chlorobenzenesulfonyl)-
imidoylacetic acid 5f. Yield 0.31 g (47%), oily compound, Rf =
0.25 (hexane–Et2O 1 : 1); dH(300 MHz, CDCl3, Me4Si) 2.16
=
(6H, s, 2CH3CO), 2.64 (3H, s, N CCH3), 5.40 (1H, s, OCH),
7.48 (2H, d, J 9.0, H-arom.), 7.75 (2H, d, J 9.0, H-arom.); m/z
(EI) 331 (M+, 4.1%), 290 (1.3), 272 (1.1), 253 (3.2), 248 (8.5),
214 (3.2), 175 (47.2), 159 (8.1), 153 (8.5), 141 (7.5), 128 (8.3),
111 (41.6), 75 (13.8), 43 (100).
3-(Acetylethoxycarbonyl)methoxy-1,2-benzisothiazole 1,1-
dioxide 4b. Yield 0.31g (50%), colorless crystals, Rf = 0.18
(hexane–Et2O 1 : 1), mp 74 ◦C (from Et2O) (Found: C, 50.2; H,
4.2; N, 4.5; S, 10.3. Calc. for C13H13NO6S: C, 50.2; H, 4.2; N, 4.5;
S, 10.3%); mmax(KBr)/cm−1 3436, 1739, 1617, 1558, 1396, 1340,
1249, 1172, 592, 536; dH(300 MHz, CDCl3, Me4Si) 1.32 (3H, t,
J 7.0, CH3), 2.46 (3H, s, CH3), 4.37 (2H, q, J 7.0, CH2), 5.9 s
(1H, OCH), 7.2–8.3 (4H, m, H-arom.); m/z (EI) 311 (M+, 2.3%),
43 (100).
Decomposition of diazoacetic ester 3d in the presence of imides
1a, 2a,b to produce O-alkylimidates 4d, 5g,h
(a) To a suspension of 0.5 g (2.7 mmol) saccharin 1a in 8 mL
of dichloromethane was added 7 mg (15.8 lmol) of dirhodium
tetraacetate, then under stirring was added dropwise over
30 min a solution of 0.66 g (5.4 mmol) diazoacetic ester 3d in
4 mL CH2Cl2 and reaction mixture was stirred for 20 min at
room temperature. The solvent was evaporated to a volume of
ca. 3 mL and residue was filtered through a small layer of silica
gel (eluent pentane–diethyl ether = 1 : 1), the main fraction was
dried with MgSO4, and after removal of the solvents the imidate
4d was recrystallized from a mixture of CH2Cl2–petroleum =
2 : 1.
(Dimethoxycarbonyl)methyl ester of N-(4-methylbenzene-
sulfonyl)imidoylacetic acid 5a. Yield 0.61g (90%), colourless
crystals, Rf = 0.33 (hexane–Et2O 1 : 1), mp 122–123 ◦C
(from CH2Cl2–petroleum) (Found: C, 49.0; H, 5.0; N, 4.1;
S, 9.3. Calc. for C14H17NO7S: C, 49.0; H, 5.0; N, 4.1; S,
9.3%); mmax(CHCl3)/cm−1 3020vs, 2940vs, 1750m, 1625m, 1154w;
=
dH(300 MHz, CDCl3, Me4Si) 2.43 (3H, s, N CCH3), 2.62 (3H, s,
CH3Ar), 3.7 (6H, s, 2 OCH3), 5.47 (1H, s, OCH), 7.31 (2H, d,
J 8.7, H-arom.), 7.75 (2H, d, J 8.7, H-arom.); m/z (EI) 343 (M+,
4.0%), 312 (2.2), 155 (76.1), 147 (47.4), 139 (6.7), 132 (3.8), 91
(100.0), 65 (21.5), 59 (9.3), 47 (10.1), 43 (7.7).
(b) To a solution of 2.55 g (12 mmol) imide 2a and 30 mg
(68 lmol) Rh2(OAc)4 in 15 mL CH2Cl2 was added dropwise
over 5 h a solution of 1.7 g (15 mmol) diazoacetic ester 3d
in 30 mL dichloromethane. On completion of the reaction
(control via TLC) the catalyst was removed by filtration of the
reaction mixture through a layer of silica gel (7 g), to obtain an
analytically pure sample of imidate 5g. The isolated compound
was additionally subjected to chromatography on silica gel (40 g,
eluent petroleum–CH2Cl2 = 1 : 1).
(Dimethoxycarbonyl)methyl ester of N-(4-chlorobenzene-
sulfonyl)imidoylacetic acid 5b. Yield 0.63 g (87%), colourless
crystals, Rf = 0.3 (hexane–Et2O 1 : 1), mp 104 ◦C (from
CH2Cl2–petroleum) (Found: C, 43.1; H, 3.9; N, 3.8; S, 8.85.
Calc. for C13H14ClNO7S: C, 42.9; H, 3.9; N, 3.8; S, 8.8%);
mmax(CHCl3)/cm−1 3024s, 2932vs, 1747m, 1619m, 1322m, 1156m,
1082m, 650m; dH(300 MHz, CDCl3, Me4Si) 2.64 (3H, s,
(c) To a suspension of the imide 2b (0.5 g; 2.1 mmol) and
10 mg (22 lmol) of Rh2(OAc)4 in 15 mL CH2Cl2 was added
dropwise with stirring over 1 h a solution of 0.48 g (4.2 mmol)
diazoacetic ester 3d in 20 mL CH2Cl2, and after work-up of the
reaction mixture in a similar way to the preceding experiment
was obtained the imidate 5h.
=
N CCH3), 3.72 (6H, s, 2 OCH3), 5.45 (1H, s, OCH), 7.49 (2H,
d, J 7.8, H-arom.), 7.81 (2H, d, J 7.8, H-arom.); m/z (EI) 363
(M+, 5.0%), 332 (7.2), 175 (77.4), 167 (37.1), 159 (10.9), 152 (6.3),
111 (95.4), 65 (24.6), 59 (8.0), 47 (9.6), 43 (8.4).
(Acetylethoxycarbonyl)methyl ester of N-(4-methylbenzene-
sulfonyl)imidoylacetic acid 5c. Yield 0.53 g (78%), oily com-
pound, Rf = 0.24 (hexane–Et2O 2 : 1); dH(300 MHz, CDCl3,
3-(Ethoxycarbonyl)methoxy-1,2-benzisothiazole 1,1-dioxide
4d. Yield 0.58 g (80%), colourless crystals, Rf = 0.2 (hexane–
Et2O 1 : 1), mp 76–77 ◦C (from CH2Cl2–petroleum) (Found:
C, 49.1; H, 4.1; N, 5.25. Calc. for C11H11NO5S: C, 49.1; H,
4.1; N, 5.2%); mmax(KBr)/cm−1 3438s, 2983vs, 1756m, 1558m,
1398m, 1332m; dH(300 MHz, CDCl3, Me4Si) 1.31 (3H, t,
J 7.2, OCH2CH3), 4.3 (2H, q, J 7.2, OCH2CH3), 5.1 (2H, s,
CH2CO2Et), 7.73–7.9 (4H, m, H-arom.). HRMS, [M + H]+:
found 270.04304, calc. 270.04307.
=
Me4Si) 1.13 (3H, t, J 7.0, CH2CH3), 2.19 (3H, s, CH3C O),
=
2.37 (3H, s, CH3Ar), 2.56 (3H, s, N CCH3), 4.08 (2H, q, J 7.0,
CH2CH3), 5.41 (1H, s, OCH), 7.25 (2H, d, J 8.1, H-arom.), 7.68
(2H, d, J 8.1, H-arom.); m/z (EI) 341 (M+, 1.2%), 326 (1.4), 300
(3.3), 274 (1.9), 258 (12.8), 254 (4.8), 211 (4.8), 198 (4.7), 171
(7.7), 155 (84.0), 108 (53.8), 91 (100.0), 65 (35.9), 49 (28.2).
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6
4 1 1 3

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(Ethoxycarbonyl)methyl ester of N-(4-methylbenzenesulfonyl)-
imidoylacetic acid 5g. Yield 1.47 g (41%), colourless liquid,
Rf = 0.23 (hexane–CH2Cl2 3 : 1), n2D0 1.5158 (Found: C, 52.2; H,
5.8; N, 4.6; S, 10.8. Calc. for C13H17NO5S: C, 52.2; H, 5.7; N,
4.7; S, 10.7%); mmax(KBr)/cm−1 2983vs, 1754m, 1621m, 1303m,
1159m, 682m; dH(300 MHz, CDCl3, Me4Si) 1.17 (3H, t, J 7.2,
the resultant substance 6c was recrystallized from a mixture of
petroleum–CH2Cl2 = 1 : 1.
N-(3ꢀ-Ethoxycarbonyl-2ꢀ-oxopropyl)-1,2-benzisothiazol-3(2H)-
one 1,1-dioxide 6c. Yield 6.8 g (46%), colourless crystals,
Rf = 0.35 (hexane–Et2O 1 : 1), mp 100–101 ◦C (from
CH2Cl2–petroleum) (Found: C, 50.2; H, 4.2; N, 4.5. Calc. for
C13H13NO6S: C, 50.2; H, 4.2; N, 4.5%); mmax(KBr)/cm−1 3469s,
2981vs, 1731m, 1330m, 1184m; dH(200 MHz, CDCl3, Me4Si)
1.27 (3H, t, J 7.0, OCH2CH3), 3.6 (2H, s, COCH2CO), 4.21
(2H, q, J 7.0, OCH2CH3), 4.67 (2H, s, NCH2), 7.83–8.03 (4H,
m, H-arom.); m/z (EI) 311 (M+, 3.2%), 265 (13.5), 266 (16.2),
196 (100.0), 169 (8.1), 132 (59.3), 115 (40.1), 104 (35.4), 87
(13.5), 76 (29.7), 50 (16.0), 43 (51.4).
=
CH2CH3), 2.42 (3H, s, CH3Ar), 2.56 (3H, s, N CCH3), 4.08
(2H, q, J 7.2, CH2CH3), 4.62 (2H, s, CH2CO2Et), 7.31 (2H, d,
J 8.4, H-arom.), 7.79 (2H, d, J 8.4, H-arom.). HRMS, [M +
H]+: found 300.09032, calc. 300.09002.
(Ethoxycarbonyl)methyl ester of N-(4-chlorobenzenesulfonyl)-
imidoylacetic acid 5h. Yield 0.19 g (28%), colourless liquid,
Rf = 0.26 (hexane–CH2Cl2 3 : 1) (Found: C, 45.1; H, 4.45; N,
4.3; S, 10.1. Calc. for C12H14NO5SCl: C, 45.1; H, 4.4; N, 4.4; S,
10.0%); mmax(KBr)/cm−1 2889vs, 1693m, 1561m, 1347m, 1130m,
636m; dH(300 MHz, CDCl3, Me4Si) 1.09 (3H, t, J 7.3, CH2CH3),
(b) A solution of Et3N (0.71 g, 7 mmol) in 5 mL CH2Cl2
was added under cooling to a mixture of N-alkyl saccharin 6c
(2 g, 6.4 mmol) and p-N-(acetyl)benzenesulfonyl azide (1.52 g,
6.7 mmol) in 10 mL CH2Cl2. The obtained mixture was stirred at
18–20 ◦C until completion of the diazotransfer process (ca. 2 h,
control via TLC). The precipitated sulfonamide was separated
by filtration, and the residue from the mother liquid after evap-
oration of the solvent and Et3N was chromatographed on silica
gel (20 g, eluent: petroleum–diethyl ether = 1 : 4). The resulting
diazocompound 11 was recrystallized from diethyl ether.
=
2.53 (3H, s, N CCH3), 4.01 (2H, q, J 7.3, CH2CH3), 4.54 (2H, s,
CH2CO2Et), 7.40 (2H, d, J 8.5, H-arom.), 7.75 (2H, d, J 8.5,
H-arom.); m/z (EI) 319 (M+, 3.8%), 274 (3.3), 216 (10), 175 (95),
152 (6.1), 128 (7.2), 111 (100.0), 103 (87.5), 75 (72.5), 59 (10.0),
50 (13.8), 42 (50).
N-Alkylation of the imide 1a using alkyl halides
(a) A solution of dimethyl bromomalonate (1 g, 4.7 mmol) in
1 mL DMF was added to 1 g (4.9 mmol) of sodium salt 1a-
Na in 2 mL DMF. The resultant mixture was heated for 3 h
at 70 ◦C, cooled, poured out into 15 mL of water, and the
precipitated N-alkylimide 6a was filtered off and crystallized
from a mixture of CH2Cl2–hexane = 1 : 1. In a similar reaction
with diethyl bromomalonate, after heating for 5 h at 120 ◦C,
N-(ethoxycarbonyl)methyl saccharin 6b was isolated in 95%
yield.
(b) A solution of 2.19 g (0.018 mol) ethyl chloroacetate in 4 mL
DMF was added to 3.69 g (0.018 mol) of saccharin 1a sodium
salt in 4 mL DMF. The resulting mixture was heated at 100 ◦C
for 8 h, cooled, poured into 20 mL of water, and precipitated
crystals of N-alkylimide 6b were filtered off and recrystallized
from a mixture of CH2Cl2–petroleum = 1 : 1.
N-(3ꢀ-Diazo-3ꢀ-ethoxycarbonyl-2ꢀ-oxopropyl)-1,2-benzisothiazol-
3(2H)-one 1,1-dioxide 7. Yield 1.8 g (84%), pale-yellow crystals,
Rf = 0.25 (hexane–Et2O 1 : 1), mp 147–148 ◦C (from Et2O)
(Found: C, 46.3; H, 3.3; N, 12.4. Calc. for C13H11N3O6S: C,
46.3; H, 3.3; N, 12.5%); mmax(KBr)/cm−1 3525vs, 2154s, 1739m,
1708m, 1673s, 1338m, 1309w; dH(300 MHz, CDCl3, Me4Si) 1.36
(3H, t, J 7.2, OCH2CH3), 4.21 (2H, q, J 7.2, OCH2CH3), 4.99
(2H, s, NCH2CO), 7.83–8.09 (4H, m, H-arom.); dC(75.5 MHz,
CDCl3, Me4Si) 14.2 (CH3CH2O), 45.2 (NCH2), 61.9 (OCH2),
=
75.7 (C N2), 121.0, 125.1, 126.9, 134.4, 135.0, 137.6 (C-arom.),
=
=
159.0 (NC O), 159.0 (CO2Et), 182.5 (CH2C O); m/z (EI) 337
(M+, 1.1%), 309 (8.3), 292 (3.7), 282 (2.3), 212 (7.9), 196 (100.0),
169 (8.3), 145 (15.3), 132 (11.1), 104 (27.9), 77 (27.8), 76 (28.0),
69 (6.9), 50 (11.6).
(c) To a solution of diazosaccharin 7 (1.0 g, 2.9 mmol)
and 3.26 g (23 mmol) DMAD in 5 mL CH2Cl2 with stirring
was added 13 mg (29.4 lmol) of dirhodium tetraacetate. The
evolution of N2 started 10 min after the addition of the
catalyst and proceeded for 12 h (control using TLC), therewith
the reaction product crystallized gradually from the reaction
mixture as a white powder. After complete decomposition of
the diazo compound 7 the precipitate of adduct 8 was filtered
off and carefully washed with dichloromethane.
N-(Dimethoxycarbonyl)methyl-1,2-benzisothiazol-3(2H)-one
1,1-dioxide 6a. Yield 0.9 g (61%), colourless crystals, Rf = 0.14
(hexane–Et2O 2 : 1), mp 156–157 ◦C (from CH2Cl2–hexane)
(Found: C, 46.0; H, 3.6; N, 4.3. Calc. for C12H11NO7S: C, 46.0;
H, 3.5; N, 4.5%); mmax(CHCl3)/cm−1 3000s, 2937vs, 2298vs,
1745m, 1340s, 1177m; dH(300 MHz, CDCl3, Me4Si) 3.87 (6H, s,
2OCH3), 5.26 (1H, s, NCH), 7.84–8.07 (4H, m, H-arom.); m/z
(EI) 313 (M+, 2.9%), 282 (3.9), 269 (18.4), 254 (84.2), 226 (36.8),
190 (26.3), 183 (68.4), 166 (18.4), 162 (13.1), 152 (15.7), 146
(28.9), 130 (13.1), 118 (10.5), 104 (76.3), 76 (100.0), 59 (42.1),
50 (55.2).
2,3-Dimethoxycarbonyl-4-ethoxycarbonyl-5-oxo-8,8-dioxo-
9,10-benzo-11-oxa-8-thia-7-aza-tricyclo[5,3,11,401,7]undec-2,9-
dien 8. Yield 0.8 g (61%), colourless crystals, Rf = 0.09
(hexane–CH2Cl2 1 : 3), mp 198–199 ◦C (from CH2Cl2) (Found:
C, 50.6; H, 3.8; N, 3.1. Calc. for C19H17NO10S: C, 50.55; H, 3.8;
N, 3.1%); mmax(KBr)/cm−1 3627m, 2956m, 1758vs, 1733vs, 1648s,
1313vs; dH(600 MHz, CDCl3, Me4Si) 1.31 (3H, t, J 7.2, CH3),
3.65 (3H, s, CH3), 3.94 (3H, s, CH3), 4.33, 4.40 (2H, dq, J 10.8,
7.12, OCH2CH3), 4.32 (1H, d, J 18.8, NCH2CO), 4.72 (1H, d,
J 18.8, NCH2CO), 7.69–7.93 (4H, m, H-arom.); dC(150 MHz,
CDCl3, Me4Si) 14.1 (OCH2CH3), 48.2 (6-C), 53.3 (OCH3), 53.6
(OCH3), 63.7 (OCH2CH3), 92.5 (4-C), 97.6 (1-C), 121.8, 126.2,
131.2 (10-C), 132.7, 134.1, 135.5 (9-C) (C-arom.), 134.6 (2-C),
N-(Ethoxycarbonyl)methyl-1,2-benzisothiazol-3(2H)-one 1,1-
dioxide 6b (R3 = CO2Et). Yield 4.3g (89%), colourless crystals,
Rf = 0.4 (hexane–CH2Cl2 1 : 1), mp 105–106 ◦C (from CH2Cl2)
(lit.,16a 107 ◦C;16b 94–95 ◦C)(Found:C, 49.2;H, 4.15;N, 5.2. Calc.
for C11H11NO5S: C, 49.1; H, 4.1; N, 5.2%); mmax(KBr)/cm−1 3446
(73), 2992 (75), 1749 (49), 1459 (64), 1267 (64); dH(200 MHz,
CDCl3, Me4Si) 1.25 (3H, t, J 7.2, OCH2CH3), 4.23 (2H, q,
J 7.2, OCH2CH3), 4.42 (2H, s, CH2CO2Et), 7.86–8.05 (4H, m,
H-arom.).
=
143.9 (3-C), 159.3, 161.2, 161.9 (all C O, ester), 184.8 (5-C);
Synthesis and catalytic decomposition of diazo saccharin 11
m/z (EI) 451 (M+, 1.1%), 423 (28.5), 350 (7.1), 331 (38.5), 286
(a) To a solution of the Na-salt of saccharin 1a (9.8 g,
(100.0), 258 (27.1), 227 (7.8), 169 (6.4), 141 (11.4), 59 (5.7).
0.048 mol) in 12 mL DMF was added 10.1 g (0.048 mol) of
◦
c-bromoacetoacetic ester under heating to 50 C. The mixture
Crystal structure determination of imidates 4c and 5b
was stirred at 90 ◦C for 3 h, cooled, poured into 100 mL of cold
water, and the precipitated crystals were filtered off, washed
with water and dried. To prepare an analytically pure sample
Single crystals of the compounds 4c and 5b suitable for X-ray
diffraction were selected directly from the analytical samples.
4 1 1 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6

View Article Online
Table 3 Crystallographic data for imidates 4c and 5b
615; C. Bolm, A. Kasyan, K. Drauz, K. Gunter and G. Raabe,
Angew. Chem., Int. Ed., 2000, 39, 2288; Y. Iso, H. Schindo and H.
Hamana, Tetrahedron, 2000, 56, 5353; M. M. Yang, X. Wang, H. Li
and P. Livant, J. Org. Chem., 2001, 66, 6729; K. Yamazaki and Y.
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2003, 5, 745; Y. Wang, Y. Zhu, Z. Chen, A. Mi, W. Hu and M. P.
Doyle, Org. Lett., 2003, 5, 3923; S.-H. Lee, B. Clapham, G. Koch,
J. Zimmermann and K. D. Janda, Org. Lett., 2003, 5, 511; F. A.
Davis, B. Yang and J. Deng, J. Org. Chem., 2003, 68, 5147; A. C. B.
Burtoloso and C. R. D. Correia, Tetrahedron Lett., 2004, 45, 3355; S.
Bachmann, D. Fielenbach and K. A. Jorgensen, Org. Biomol. Chem.,
2004, 2, 3044; H. Matsushita, S.-H. Lee, K. Yoshida, B. Clapham,
G. Koch, J. Zimmermann and K. D. Janda, Org. Lett., 2004, 6,
4627.
6 B. Schulze, D. B. Gidon, A. Siegemund and L. L. Rodina, Heterocy-
cles, 2003, 61, 639; D. B. Gidon, Vs. V. Nikolaev, L. L. Rodina and
B. Schulze, Proceedings of the Third School-Conference on Organic
Synthesis (YSCOS-3), Izd. StPSU, St. Petersburg, 2002, p. 90.
7 (a) H. Hettler, Adv. Heterocycl. Chem., 1973, 19, 233; (b) D. J.
Pain, B. J. Peart and K. R. H. Wooldridge, ‘Isothiazoles and
their Benzo Derivatives’, in Comprehensive Heterocyclic Chemistry,
A. R. Katritzky and C. W. Rees, eds., Pergamon Press, Oxford, 1984,
vol. 6, p. 131; (c) B. Schulze and K. Illgen, J. Prakt. Chem., 1997,
339, 1.
Parameter
4c
5b
Formula
Crystal system
C12H10NO5S
Triclinic
P1
C13H14NO7ClS
Triclinic
¯
¯
Space group
P1
˚
a/A
7.6162(5)
9.1924(5)
10.6592(6)
107.647(1)
97.265(1)
110.172(1)
644.88(7)
2
8.051(1)
8.774(2)
11.745(2)
91.894(3)
105.771(3)
90.555(3)
797.9(2)
2
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
Dc/g cm−3
1.443
0.266
28.6
1.514
0.405
27.0
4891/3383
0.0159
l(Mo ◦Ka)/mm−1
2hmax
/
Measured/unique reflections
Rint
Parameters refined
R1, wR2 [I > 2r(I)]
R1, wR2 (all data)
4173/2907
0.0138
217
0.0379, 0.1069
0.0417, 0.1104
264
0.0425, 0.1046
0.0639, 0.1219
8 Formally, compounds in hand are mixed imides of arenesulfonic and
carboxylic acids having the SO2–NH–CO fragment in their structure.
Thus, we will use for them a general name ‘sulfonimides’ to distinguish
these substrates from ‘sulfonamides’ with the SO2–NH2 moiety in the
structure, which also occur in this research.
9 (a) M. Hrytsak and T. Durst, Heterocycles, 1987, 26, 2393; (b) S. N.
Osipov, N. Sewald, A. F. Kolomiets, A. V. Fokin and K. Burger,
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1907.
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Chem., 1953, 18, 1030; (b) G. Bartels, R.-P. Hinze and D. Wullbrandt,
Liebigs Ann. Chem., 1980, 168; (c) A. C. Lottes, J. A. Landgrebe and
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and E. J. Corey, Org. Lett., 2000, 2, 1641.
11 For a preliminary communication, see: B. Schulze, Vs. V. Nikolaev,
L. Hennig, L. L. Rodina, J. Sieler and V. A. Nikolaev, Russ. J. Org.
Chem., 2004, 40, 740.
12 D. G. Neilson, in The Chemistry of Amidines and Imidates, S. Patai
and Z. Rappoport, eds., John Wiley & Sons Inc., Chichester,
1991, vol. 2, p. 425; D. G. Neilson, in The Chemistry of Amidines
and Imidates, S. Patai, ed., Wiley-Interscience Inc., London, 1975,
p. 385.
13 C. O. Meese, W. Walter and M. Berger, J. Am. Chem. Soc., 1974, 96,
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1986, 51, 3266.
Crystallographic measurements were made using an AXS
BRUKER 1 K CCD-detector (graphite monochromated Mo
˚
Ka radiation (k = 0.71073 A), empirical absorption correction
using SADABS.27a The essential experimental conditions and
crystal data are given in Table 3. The structures were solved
by direct methods and refined in the anisotropic approximation
for the non-hydrogen atoms using SHELXS-86 and SHELXL-
97.27b,c All H atoms were located by difference Fourier map and
refined isotropically.
CCDC reference numbers 270185 (4c) and 270186 (5b). See
http://dx.doi.org/10.1039/b508317f for crystallographic data
in CIF or other electronic format.
Acknowledgements
The authors are thankful to Professors H. L. M. Davies and
A. Padwa for helpful discussions of the results obtained in this
research while at the Symposium on Diazo Chemistry in St.
Petersburg, Russia.
14 V. Mizrahi, T. Hendrickse and T. A. Modro, Can. J. Chem., 1983,
61, 118; M. Caswell and G. L. Schmir, J. Am. Chem. Soc., 1979, 101,
7323.
15 G. Brooks, T. T. Howarth and E. Hunt, J. Chem. Soc., Chem.
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17 K. Ueda, T. Ibata and M. Takebayashi, Bull. Chem. Soc. Jpn., 1972,
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18 M. C. McMills and D. Wright, ‘Carbonyl Ylides’, in Synthetic
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19 R. Gommper, Angew. Chem., Int. Ed. Engl., 1964, 3, 560; O. A.
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5 For recent publications on this reaction see, for example: E.
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O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6
4 1 1 5

View Article Online
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4 1 1 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 1 0 8 – 4 1 1 6