Sulfene

Preparation

The first general method for preparation of sulfene as an intermediate, reported simultaneously in 1962 by Gilbert Stork and by Günther Optiz, involved the removal of hydrogen chloride from methanesulfonyl chloride using triethylamine in the presence of an enamine as trapping agent. The formation of a thietane 1,1-dioxide derivative was taken as evidence for the intermediacy of sulfene. Because of the highly electrophilic character of sulfene, the use of amines presents difficulties, since they can intercept the sulfene to form adducts. A simple alternative which avoids the use of amines involves desilylation of trimethylsilylmethanesulfonyl chloride with cesium fluoride in the presence of trapping agents.

: (CH3)3SiCH2SO2Cl + CsF → [CH2=SO2] + (CH3)3SiF + CsCl

Alternatively, sulfenes can be stabilized by installing amido substituents on the alkylidene substituent. The extreme case is thiourea dioxide, which features planar amido groups. :[[File:SURDOX.png|thumb|left|Structure of thioureadioxide ((H2N)2CSO2). Selected distances and angles: rS=O = 1.49, rS=C = 1.85.1, rC-N = 1.31 Å, sum of angles around S = 312.4°.]]

Reactions

Sulfenes react with enamines, ynamines, and 1,3-cyclopentadienes to give thietanes, thietes and Diels-Alder adducts, respectively. In the presence of a chiral tertiary amine complex, several sulfenes could be trapped with trichloroacetaldehyde (chloral) in a catalytic asymmetric synthesis of β-sulfones (four-membered ring sulfonate esters). Sulfene can also undergo insertion into metal–hydrogen bonds.

References

References

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