Au/Ag-Catalyzed Intramolecular Ring-Opening of Vinylidene-cyclopropanes (VDCPs): An Easy Access to Functional Tetrahydropyrans
摘要:
An intramolecular ring-opening of vinylidenecyclopropanes (VDCPs) tethered with alcohol chains has been established. A series of transition metal catalysts and their combinations have been screened under mild conditions, and a cocatalyst system consisting of [(Ph3PAu)(3)O]BF4 (4 mol %) and AgOTf (4 mol %) was found to catalyze the reaction to completion within 10-30 min in 1,4-dioxane at 60 degrees C to give allene-functionalized tetrahydropyrans.
Rhodium(I)-Catalyzed Intramolecular Ene Reaction of Vinylidenecyclopropanes and Alkenes for the Formation of Bicyclo[5.1.0]octylenes
作者:Wei Li、Wei Yuan、Min Shi、Erik Hernandez、Guigen Li
DOI:10.1021/ol902505p
日期:2010.1.1
An efficient catalytic system for the intramolecular ene reaction of allene and alkene of diarylvinylidenecyclopropanes has been established. The reaction was achieved by using [RhCl(CO)(2)](2) as the catalyst In co-solvents of toluene and acetonitrile. MeCN was found to play a crucial role in controlling the reaction toward formation of bicyclo[5.1.0]octylene derivatives. An alternative system consisting of [RhCl(CO)(2)](2) and toluene in the absence of MeCN was found to give [2 + 2] cycloaddition adducts. The structures have been unambiguously determined by X-ray structural analysis. Deuterium labeling experiments were conducted to confirm the mechanism hypothesis.