Highly regioselective Wittig reactions of cyclic ketones with a stablized phosphorus ylide under controlled microwave heating

摘要

Significant base and temperature effects on the Wittig reactions of cyclohexanones with (carbethoxymethylene)triphenyl-phosphorane under microwave irradiation were observed.For the Wittig reactions carried out in a domestic microwve oven under solvent-free conditons,the initially formed exo-olefin products isomerized into the thermodynamically more stablej endo-olefins due to uncontrolled high reaction temperature.In sharp contrast,under controlled microwave heating,both exo-and olefins have been selectively synthesized by accurately regulating the reaction temperature with or without a base.