PtCl2-Catalyzed Conversion of 1,6- and 1,7-Enynes to 1-Vinylcycloalkenes. Anomalous Bond Connection in Skeletal Reorganization of Enynes

The treatment of 1,6- and 1,7-enynes with a catalytic amount of PtCl2 in toluene at 80 °C results in skeletal reorganization (cyclorearrangement) of the enynes to give 1-vinylcycloalkenes in high yields. A deuterium labeling experiment indicates that two mechanistic paths are operating for the cyclorearrangement. The nature and position of substituents affect the reaction course. Anomalous carbon−carbon bond formation is attained selectively in the reaction of 1,6-enynes having an ester group at the terminal acetylenic carbon.