ALPHA-HALO SULFONES .12. CHLORINATION OF BRIDGEHEAD SULFIDES AND SULFONES . TRANSANNULAR DOUBLE-BOND FORMATION IN BASE-INDUCED REARRANGEMENT OF BRIDGEHEAD ALPHA-CHLORO SULFONES

Direct chlorination-oxidation of 9-thiabicyclo[3.3.1]nonane (2) and 8-thiabicyclo[3.2.1]octane (11) did not result in the expected introduction of an α-chloro substituent. Rather, endo-2-chloro sulfones were produced; these unprecedented reactions very likely proceed via a cleavage-recombination mechanism involving intermediate sulfenyl chlorides. Treatment of the 2-chloro sulfones with potassium t-butoxide led to replacement of halogen by t-butoxy with retention of configuration, the stereochemical outcome requiring the intervention of highly strained α,β-unsaturated sulfones in which the double bonds occupy bridgehead positions. The sulfones derived from 2 and 11 lent themselves to facile bridgehead carbanion formation. Treatment of such carbanions with sulfuryl chloride and thermal desulfonylation of the resulting bridgehead sulfonyl chlorides permitted synthetic entry to the required bridgehead a-chloro sulfones, the base-induced rearrangement of which was examined as a method for the controlled introduction of transannular double bonds. © 1969, American Chemical Society. All rights reserved.