Sequential carboxylation/intramolecular cyclization reaction of o-alkynyl acetophenone with CO2

Abstract

A novel sequential carboxylation/intramolecular cyclization reaction of o-alkynyl acetophenone with CO₂ was developed for producing the synthetically important 1(3H)-isobenzofuranylidene acetic acids and esters in good yield and exclusive selectivity toward 5-exo oxygen cyclization under very mild reaction conditions (room temperature and CO₂ balloon). This efficient reaction system showed wide functional group compatibility. Also, the computational study successfully explained the exclusive product selectivity toward the 5-exo oxygen cyclization product.