Efficient synthesis of novel gamma-substituted gamma-butenolides by Lewis acid catalyzed addition of metal enolates of active methylene compounds to mucohalic acids.

Lewis acid catalyzed addition of active methylene compounds to mucochloric acid (1) and mucobromic acid (2) affording Knoevenagel aldol adducts, gamma-substituted gamma-butenolides, has been explored. Catalytic efficiencies of various Lewis acids have been compared. Indium acetate (0.25-5 mol %) was found to be the most efficient catalyst.