Domino ring opening/cyclization of oxiranes for synthesis of functionalized 2H-pyran-5-carboxylate.

A simple method for the synthesis of functionalized 2H-pyrans via a catalytic reaction of an oxirane, an alkyne, and a malonate has been developed in which a 6-exo-dig cyclization pathway is observed. In this transformation, the attack of in situ generated copper acetylides on oxiranes formed homopropargylic alcohol intermediates which further transferred to 2H-pyrans with the help of malonates.