Sulfur Dioxide: A Powerful Tool for the Stereoselective Construction ofCCBonds

Abstract

For a long time, the use of sulfur dioxide in organic chemistry was limited to the synthesis of simple bulk materials such as sulfinate salts and sulfones. Conjugate bases of sulfones are carbon nucleophiles that can be used to construct CC single bonds and stereoselective CC double bonds. Sulfones can also be employed as electrophiles, for instance, in the stereo‐ and enantioselective α‐aminoalkylations of carbonyl compounds. α,β‐Unsaturated sulfones are excellent acceptors in asymmetric Michael additions. They are also good dienophiles. Sulfones and readily available sulfonyl chlorides are good electrophilic partners in desulfinylative CC cross‐coupling reactions catalyzed by transition metals, including iron. Sulfur dioxide undergoes reversible cheletropic additions with 1,3‐dienes and irreversible metallo‐ene reactions with allylmetals. Conditions have been found realizing the endergonic H‐ene reactions of SO 2 with alkenes. This permits the one‐pot synthesis of polyfunctional sulfinates, sulfones, and sulfonamides starting from alkenes. At a low temperature, the hetero‐Diels‐Alder additions of SO 2 generate unstable sultines that can be used as electrophiles in the stereoselective construction of CC bonds between electron‐rich alkenes and 1,3‐dienes. The reaction cascade permits the one‐pot construction of stereotriads and stereotetrads that can be used subsequently in two successive aldol reactions that give, in short ways (double chain elongation), long‐chain polyketide and polypropionate antibiotics.