Russian Journal of Organic Chemistry, Vol. 37, No. 8, 2001, pp. 1149 1152. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 8, 2001,
pp. 1208 1211.
Original Russian Text Copyright
2001 by Babii, Zyabrev, Drach.
Conversion
of N-(1-Arylsulfonyl-2,2-dichloroethenyl)carboxamides
into Derivatives of 4,5-Dimercaptooxazole
S. B. Babii, V. S. Zyabrev, and B. S. Drach
Institute of Bioorganic Chemistry and Petrochemistry,
Ukrainian National Academy of Sciences, Kiev, O2094, Ukraine
Received August 25, 2000
Abstract In reaction of excess thiols with -arylsulfonyl-substituted enamides containing two chlorine atoms
in -position to the amide moiety the chlorine atoms and the arylsulfonyl group attached to the C=C bond
are replaced by alkylthio or arylthio groups. The sulfur-containing enamides obtained undergo cyclization
when treated with phosphorus pentachloride or thionyl chloride to furnish 4,5-dimercaptooxazoles used for
preparation of the corresponding disulfonyl derivatives. The latter were also obtained by treating in
succession the N-(1-arylsulfonyl-2,2-dichloroethenyl)carboxamides with sodium hydrosulfide, then with
alkyl halides, and hydrogen peroxide in acetic acid.
We recently showed that with the use of chloral,
carboxamides, and sodium arenesulfinates could be
easily prepared sulfur-containing enamides I capable
of versatile transformations [1 3]. In the present
study we systematically investigated the condensation
of electrophilic reagents I with various thiols and thus
established a close relation of these enamides with
quite a number of important acyclic and heterocyclic
compounds II X shown in a scheme.
presence of phosphorus pentachloride or thionyl
chloride. As a result arise previously unknown sub-
stituted 4,5-dimercaptooxazoles VIII. With the use
of IR spectroscopy we confirmed the participation of
the acylamine group in the formation of the oxazole
ring, and the elimination of one alkylthio or arylthio
group is in agreement with elemental analysis and
1H NMR spectra (Table 1). The presence in com-
pounds VIII of two substituted thiol groups was
proved by their conversion into the corresponding
disulfonyl derivatives of 2-alkyl or 2-aryloxazoles IX.
It is also important that certain representatives of
compounds IX were prepared by an independent
procedure: the treatment of enamides I first with
sodium hydrosulfide and then with alkyl halides and
hydrogen peroxide in acetic acid [see transformations
First of all note that in reaction of enamides I with
thiols in the presence of triethylamine we were able
sometimes to isolate the expected products with
chlorine atoms at the C=C bond substituted by the
corresponding alkylthio or arylthio groups. However
compounds II are not at all the final condensation
products since at further action of thiols they readily
afford sulfur-containing enamides VI. The substitu-
tion of arylsulfonyl group occurs apparently not at
the C=C bond of intermediate compounds II but at
C=N bond of prototropic tautomers thereof V that
are likely to arise at least in a small amount in keep-
ing with the general character of enamido acylimine
tautomerism [4]. The step-by-step performance of
transformations I II VI provides a possibility to
introduce various substituents to the sulfur atoms.
If the desired compound VI should contain all sub-
stituents alike enamides I should be treated at once
with excess thiol in the presence of triethylamine.
I
VII
X
IX on the scheme]. We discovered
before the cyclocondensation of enamides I with
sodium hydrosulfide [2] but the application of this
reaction to the synthesis of 2-alkyl(aryl)-5-alkyl(aryl)-
sulfonyl-4-arylsulfonyloxazoles was done for the first
time.
It is obvious that the planned conversion of
accessible enamides I into substituted 4,5-mercapto-
oxazoles VIII and their disulfonyl analogs IX is of
considerable preparative interest. No approach was
formerly developed to the synthesis of these promis-
ing compounds as showed the enumeration of the few
preparation cases of sulfur-containing oxazoles in the
recent fundamental monograph [5].
The specific feature of sulfur-containing enamides
VI consists in their ability to cyclocondensation in the
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