Lithiated Dimethylketene Diisopropyl Dithioacetal as a Synthon of Homoenolate Dianion of Isobutyric Ester. An Application to the Synthesis of α-Methylenelactones
Lithium anion of dimethylketene diisopropyl dithioacetal reacted with various kinds of electrophiles to afford γ-substituted products with high regioselectivity. The utility of the lithiated ketene dithioacetal, a novel homoenolate dianion equivalent of isobutyric ester, was demonstrated in the synthesis of α-methylenelactones.