ChemInform Abstract: Synthesis of 1,3‐Dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates via Intramolecular Cyclization of 2‐[2‐(Dimethoxymethyl)phenyl]‐2‐hydroxyalkanoates Followed by Oxidation.

Abstract

A novel and efficient method for the preparation of 1,3-dihydro-3-oxo-2-benzofuran-1-carboxylates 4 under mild conditions has been developed. Thus, the reaction of [2-(dimethoxymethyl)phenyl]lithiums, generated easily from 1-bromo-2-(dimethoxymethyl)benzenes 1, with α-keto esters gives the corresponding 2-[2-(dimethoxymethyl)phenyl]-2-hydroxyalkanoates 2. The TsOH-catalyzed cyclization of these hydroxy acetals is followed by the oxidation of the resulting cyclic acetals 3 with PCC to give the desired products in satisfactory yields. The reaction of [2-(dimethoxymethyl)-4,5-dimethoxyphenyl]lithium with (MeOCO)2, followed by treatment with NaBH4 or organolithiums, affords 2-[2-(dimethoxymethyl)-4,5-dimethoxyphenyl]-2-hydroxyalkanoates 6, which can similarly be transformed into the corresponding 1,3-dihydro-3-oxo-2-benzofuran-1-carboxylates 7 in reasonable yields.