Synthesis of 2-alkylbenzofurans via acid-catalyzed cyclization of 1,1-dimethoxy-2-phenoxyalkanes

Treatment of 2-phenoxyalkanals 1a-e with methanol at room temperature under homo-or heterogeneous acid-catalysis conditions leads to formation of diacetal as well as some quantities of appropriate 2-alkylbenzofurans. 2-Alkylbenzofurans 3a-e were obtained in high yields via cyclization of the 1,1-dimethoxy-2-phenoxyalkanes 2a-e under mild conditions over Amberlyst 15.