Application of Intramolecular Carbenoid Reactions in Organic Synthesis

Abstract

A Rh(II)-catalyzed formal [3+3] cyclization of diazonaphthoquinones and propargyl alcohol is reported to afford 2,3-dihydro-1,4-benzodioxins. Various terminal propargyl alcohols react with diazonapthoquinone in the presence of Rh2(OAc)4 to give the corresponding dihydrodioxins in good to high yields. However, dihydrodioxins are not formed in the reaction of internal propargyl alcohols, and the O–H insertion product and 2,5-dihydrofurans are formed as the main product(s) depending on the terminal substituent. 2,3-Dihydro-1,4-benzodioxins are proposed to be formed via Rh(II)-catalyzed intermolecular oxonium ylide formation and subsequent 6-exo-dig cyclization with the internal alkynyl group.