Lewis Acid/Base Catalyzed [2+2]-Cycloaddition of Sulfenes and Aldehydes: A Versatile Entry to Chiral Sulfonyl and Sulfinyl Derivatives

The first catalytic asymmetric synthesis of β‐sultones is reported. This development has enabled a rapid access to a number of highly enantioenriched biologically interesting sulfonyl and sulfinyl compound classes, which makes use of the inherent ring strain of the four‐membered heterocycles. The products possess either two vicinal stereocenters, such as in β‐hydroxy‐sulfonamides, ‐sulfonates, ‐sulfones, ‐sulfonic acids, ‐sulfinic acids, γ‐sultines, and γ‐sultones or a single stereocenter, such as in α‐branched alkyl or allyl sulfonic acids. This work also represents the first application of sulfene intermediates in asymmetric catalysis. The reactivity of a sulfene normally acting as an electrophile could be reverted by the formation of a nucleophilic zwitterionic sulfene–amine adduct. To achieve a combination of high enantioselectivity and reactivity, cooperative catalytic action of a chiral nucleophilic tertiary amine (the cinchona alkaloid derivative diydroquinine 2,5‐diphenyl‐4,6‐pyrimidinediyl diether ((DHQ)2PYR)) and Bi(OTf)3 or In(OTf)3 was of primary importance. SO versatile: The development of a catalytic asymmetric synthesis of β‐sultones enables rapid access to a number of highly enantioenriched sulfonyl and sulfinyl compound classes (see scheme), which makes use of the inherent ring strain of the four‐membered heterocycles. This work represents the first application of sulfene intermediates in asymmetric catalysis.