Michael Additions of Allylic Sulfones

Abstract

Recent methodology employing sulfone chemistry indicates that sulfones are becoming widely recognized as versatile intermediates in organic chemistry.¹ In particular, the anions of allylic sulfones have proven especially valuable for the synthesis of vitamin A,² chrysanthemic acid³ and presqualene alcohol.⁴ In the latter two cases the allylic sulfone anion added by a conjugate addition to an unsaturated ester to afford, after elimination of sulfinate anion, a cyclopropyl ester. We wish to report that Michael additions of allylic sulfone anions generated at -78[ddot]C with n-butyl lithium provide high yields of sulfone adducts with unsaturated ketones and esters. The results of our study are compiled in the Table below. One striking feature of this Table is the regiochemical purity of the resulting adducts. The contrast between acyclic Michael acceptors and cyclohexenone is also quite