1,2ꢀOxathiolanꢀ5ꢀone 2ꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 12, December, 2009 2497
relative to the ring plane13 was demonstrated by the exꢀ
ample of 5ꢀarylꢀ1,2ꢀoxathiolane 2ꢀoxides (γꢀsulthines) by
1H NMR spectroscopy. Similar results were observed for
monoꢀ and disubstituted 1,2ꢀoxathiolanꢀ5ꢀone 2ꢀoxides
1. In the case of 4ꢀmethylꢀsubstituted anhydride 1с, one
should expect that different cyclization methods would
afford different stereoisomers (see Schemes 1 and 2). Howꢀ
Scheme 4
(1 equiv.)
1
ever, analysis of the Н NMR spectra (recorded on the
same instrument and in the same solvent)* of samples of
1с, obtained by different methods showed that in both
cases mixtures of cis and trans isomers formed with the
prevalence of the latter. The share of cis 1с was ~16—22%
in the product obtained according to the method deꢀ
scribed earlier2 and ~19% in the case of the new method A
(with AcONa). In the product obtained using of Hg(OAc)2
(method B), the share of cis isomer in anhydride 1с was
within 19ꢀ35%.
dure for the synthesis of 1,2ꢀoxathiolanꢀ5ꢀone 2ꢀoxides 1
and 3Hꢀ2,1ꢀbenzoxathiolꢀ3ꢀone 1ꢀoxide 2 consisted in
cyclization of 3ꢀchlorosulfinylalkanoyl chlorides 3 and 4
under the action of AсONa or Hg(OAс)2 is proposed. The
method allows one to obtain carboxylicꢀsulfinic anhyꢀ
drides containing various substituents in the heterocycle,
including chloroꢀsubstituted ones, under mild conditions.
Experimental
The IR spectra were recorded on a URꢀ20 spectrophotometer
in a liquid film and in KBr pellets (for solids). The 1H NMR
spectra were recorded on a Bruker Avance 300 spectrometer
using HMDS as the internal standard. Anhydrous reagents and
solvents purified according to known procedures14 were used in
all experiments.
Compound
R
X
Percentage (%)
trans
81
cis
19
50
50
1c
1d
1e
Me
H
Me
H
Cl
Cl
50
50
The starting sulfinyl chlorides 3a—e and 4 were synthesized
as described earlier.1,3 Silufol UVꢀ254 plates were used for TLC
(visualization with iodine vapor). The purity of carboxylicꢀ
sulfinic anhydrides was also checked by titration (with NaOH or
KMnO4). Oxidimetry was carried out according to a known
procedure.2 The amount of the starting sulfinyl chlorides as
admixtures in various fractions of the obtained anhydrides was
determined by chlorine content in the sample (the Vollhardt
titration) and by 1H NMR spectra. The yields and the properties
of synthesized compounds 1a—e and 2 are listed in Table 1,
4ꢀChloroꢀ (1d) and 4ꢀmethylꢀ4ꢀchlorooxathiolanone
oxide (1e) according to the data from H NMR spectra
1
(see Table 2) are mixtures of two stereoisomers in a 1 : 1
ratio (see above). Due to structural features (proximity of
Me and S=O groups), 3ꢀmethylꢀsubstituted anhydride 1b
synthesized by both the oxalylꢀchloride method (see
Scheme 1)2 and the new method (see Scheme 2) apparꢀ
ently has trans configuration because only one signal for
the Ме group was observed in the 1Н NMR spectrum (see
Table 2).
1
spectral (IR, H NMR) and titration data are listed in Table 2.
1,2ꢀOxathiolanꢀ5ꢀone 2ꢀoxides (1а—с). Method A.
A solution of 3ꢀ(chlorosulfinyl)alkanoyl chloride 3а—с (0.1 mol)
in CHCl3 (60 mL) was added with stirring and cooling with cold
water (≤15 °С) to a suspension of freshly fused ground sodium
acetate (9.02 g, 0.11 mol) in CHCl3 (75 mL). After stirring for
1.5—2 h at 20 °С, the reaction mixture was heated on stirring
for 2 h at 65—70 °С (in a water bath) and cooled to 20 °С. The
precipitate of NaCl was filtered off and washed with chloroform.
The filtrate was concentrated in vacuo, the residue was distilled.
Method B. 1,2ꢀOxathiolanꢀ5ꢀone 2ꢀoxides 1b,c were
obtained from the corresponding chlorides 3b,с (0.1 mol)
analogously to method A, Hg(OAc)2 (35.06 g, 0.11 mol) being
used instead of sodium actate; the reaction is exothermic.
4ꢀChloroꢀ1,2ꢀoxathiolanꢀ5ꢀone 2ꢀoxide (1d). Method C.
Ground freshly fused sodium acetate (4.92 g, 0.06 mol) was
added portionwise with stirring to a solution of 2ꢀchloroꢀ
3ꢀ(chlorosulfinyl)propionyl chloride 3d (12.6 g, 0.06 mol) in
In addition, attempts of selective synthesis of anhyꢀ
dride 1b were undertaken using other Oꢀnucleophiles.
However, in the absence of a catalyst sulfinyl chloride 3b
reacted with neither oxalic acid nor (COONa)2, and the
addition of Et4NBr resulted in polymerization. The reacꢀ
tion of 3b with potash (pKB 3.7), which is a stronger base
than AcONa, afforded a mixture of anhydride 1b and the
starting compound 3b (~1 : 1) due to the competitive
reaction of complete saponification (see Scheme 4).
Thus, we have established that the most appropriate
reagent with regard of basicity for selective cyclization
is the acetate anion (pKB 9.3). A new synthetic proceꢀ
* The values for δ and J of 1c corresponded to those presented in
Table 2, but not to those reported earlier.2