A number of 1-alkenyl sulfoxides bearing either a diphenylmethyl (DPM) or a p-methoxybenzyl
(PMB) group have been prepared and exposed to the chlorine surrogate SO2Cl2. Through an
oxidative fragmentation reaction, a new family of sulfur acid derivatives, 1-alkenesulfinyl chlorides,
is generated. They can be characterized by IR spectroscopy before chemical capture with an alcohol.
Ethenesulfinyl chloride (2a) and 1-propenesulfinyl chloride (2b), obtained from their corresponding
DPM precursor, can be distilled at reduced pressure to afford ca. 90% pure material. NMR chemical
shift comparison of various 1-alkenesulfinyl-containing compounds is made. 1-Alkenesulfinylmethyl
phenyl(alkyl) ketones (6) can be prepared directly from sulfinyl chlorides 2 although decomposition
and/or isomerization is sometimes extensive during purification.
Enantiomerically enriched α,β-unsaturated sulfinate esters of ()-cholesterol undergo stereospecific substitutions at sulfur when treated in benzene at 6°C with Grignard reagents. Sulfoxides with ees of 8599.5% are obtained when enantiopure sulfinates are used. The substitution reactions proceed with inversion of sulfur configuration. Enantiomerically pure cholesteryl (E)-2-carbomethoxyethenesulfinate is not a suitable reactant under the Grignard reaction conditions. It is suggested that the ester group induces unwanted reactions significantly lowering both the yield and sulfur stereogenicity.Key words: sulfinate, sulfoxide, Grignard reagents, stereospecific, unsaturated.
The preparation of a collection of alkyl, aryl, and 1-alkenyl 2-(trimethylsilyl)ethyl sulfoxides is outlined, using mostly vinyltrimethylsilane or 2-(trimethylsilyl)ethanesulfenyl chloride (5) as key starting materials. The 2-(trimethylsilyl)ethyl group can be cleaved from many of the sulfoxides under oxidative fragmentation conditions using sulfuryl chloride and the reaction represents a new protocol for sulfinyl chloride synthesis. The method is suitable for most alkane-and arenesulfinyl chlorides (3), but is limited to highly substituted vinylic sulfinyl chlorides. 1-Alkenyl 2-(trimethylsilyl)ethyl sulfoxides with reduced double bond substitution (6, 7, 11) suc-The sulfinyl chloride unit is one of the fundamental building blocks of organosulfur chemistry. [1] It is not only the ultimate starting unit for many sulfinic acid derivatives, [2] but also for a number of sulfonyl-containing functionalities. [3Ϫ6] Sulfinyl chlorides remain one of the key starting points in the preparation of enantioenriched sulfoxides through the intermediacy of chiral sulfinic esters [1,7,8] and amides. [9,10] An extension of that chiral sulfinate chemistry ties to the burgeoning field of asymmetric sulfinimine chemistry and the synthetic diversity that it offers. [11,12] Many preparations of sulfinyl chlorides involve oxidations of a sulfur atom. [1,13] That atom may belong to a thiol, disulfide or thiolacetate and the resulting sulfinyl chloride must be separated from acidic by-products or otherwise treated in the presence of those by-products. A less common protocol entails starting with a sulfoxide and effecting CϪS bond cleavage by way of oxidative fragmentation conditions (Scheme 1). Such a method circumvents the acidic conditions of older procedures and provides a sulfinyl chloride readily available for further functionalization. In this regard, the phthalimidomethyl [14,15] and tert-butyl [16] groups have proved useful for the generation of a number of alScheme 1[a] Guelph-
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