Hexamethyldisilazanes mediated one-pot intramolecular Michael addition–olefination reactions leading to exo-olefinated bicyclo[6.4.0]dodecanes

Abstract

A novel one-pot reaction for the synthesis of exo-olefinated bicyclo[6.4.0]dodecanes 23 has been developed on the basis of an intramolecular Michael reaction of phenylsulfonyl compounds 4 with potassium hexamethyldisilazide (KHMDS) and a sequential reaction with an excess of methoxymethyl chloride (MOMCl). By this reaction, an exo-olefin group was regioselectively introduced at the α-position to the carbonyl group in the 6-membered ring in high yield. The regioselective introduction of the olefin moiety could be envisaged to proceed through a Mannich-type reaction involving the aminomethylating agent 24, which, in turn, is generated in situ by the action of HMDS on MOMCl.