REACTION OF PHOSPHONATE-STABILIZED CARBANIONS WITH CYCLIC ENONES BEARING A BETA-LEAVING GROUP

摘要

Reaction between alpha-lithiated alkylphosphonic esters and alpha,beta-unsaturated cyclopentenones and cyclohexenones carrying a heteroatom substituent Y in the beta-position was studied. Complete chemoselectivity was observed as a function of substituent Y. For Y = OMe exclusive addition-elimination at the beta-carbon was observed, yielding alpha,beta-unsaturated delta-ketophosphonates. The beta-chloro-substituted substrates (Y = Cl) derived from cyclohexenone reacted exclusively at the carbonyl carbon, yielding (2-hydroxyalkyl)phosphonates with the retained chlorovinyl function. The alcohols, depending on the conditions, could be dehydrated to two different products. The reaction of 3-chlorocyclopent-2-en-1-one with diethyl (lithiomethyl)phosphonate occurred at the beta-carbon, but the ketophosphonate product was isolated in a stable enolic form.