Dichlorocarbene Adducts of Sulfolenes and Their Chlorine Reduction Products: Hydrogen Chloride vs. Sulfur Dioxide Elimination. Thiopyran Dioxides and Thiopyrones

Article abstract of DOI:10.1021/jo00335a037

Substituted 6,6-dichloro-3-thiabicyclo<3.1.0>hexane 3,3-dioxides (1) were prepared from sulfolenes (4) in a catalytic biphasic system and reduced with lithium aluminum hydride to monochlorinated (2) and dechlorinated products (3).Several of the chlorinated bicyclic sulfones (1 and 2) were found to undergo a simultaneous thermal elimination of hydrogen chloride and sulfur dioxide.Selective elimination of hydrogen chloride, with formation of thiopyran dioxides (9,10) through ring enlargement, was achieved under basic conditions (use of lithium diisopropylamide).Somewhat less selective was the fragmentation of the dichlorinated sulfones 1 in aqueous acids.Two isomeric thiopyran dioxides (9, 12) were the major products in hydrochloric acid, while further transformation of these products, with formation of thiopyrone derivatives 14-16, was occuring in hydrobromic acid.A seven-membered dienylic sultine (21) was formed in the reaction of one of the monochlorinated sulfones (exo-Cl-2c) with n-butyllithium.