Abstract
Ruthenium catalyst TpRuPPh 3 (CH 3 CN) 2 Cl is found to effect the cyclization of epoxyalkynes to furans in the presence of Et 3 N. The reactions worked well for various epoxyalkynes with suitable oxygen and nitrogen functionalities with low loading of catalyst. It failed with disubstituted epoxyalkynes. The mechanism was elucidated by a deuterium labeling experiment that suggested that the mechanism involved a ruthenium-vinylidenium intermediate.