ACID CATALIZED RING CLOSURE REACTINOS OF ELECTROPHILIC ALKENES

Article abstract of DOI:10.1016/0040-4020(82)80073-2

Treatment of α-acyl-α,β-unsaturated ketones with sulfuric acid or dimethylformamide-hydrogen chloride or p-toluenesulfonic acid gave rise to 3-acyl-2-alkyl-4,5-dihydrofurans.Similar cyclization of α-acyl-α,β-unsaturated esters initially afforded 3-alkoxycarbonyl-2-alkyl-4,5-dihydrofurans which were transformed into 2-acylbutanolides on further reaction with sulfuric acid.This acid catalized cyclization is strongly dependent upon the substitution pattern of the electrophilic alkenes, the acid used and reaction conditions.