Takai Olefination

AbstractThis reaction is a coupling between aldehydes and geminal dihaloalkanes to form olefins in the presence of chromous chloride and is generally known as the Takai olefination. This reaction is also known as the Takai–Utimoto olefination. It is important that the coupling of aldehydes with iodoform results in the terminal iodo‐olefins primarily in thetrans‐configuration, and the resulting iodo‐olefins can be used for other couplings, such as the Stille coupling. In generally,trans‐alkenes are formed in preference from the Takai olefination, with a reported E/Z ratio varying from 4.3:1 to 20:1. Although the use of dioxane as the co‐solvent can further enhances the stereoselectivity in favor of thetrans‐configuration. On the other hand, it has been reported that the reaction rate as well as the yield can be increased by mechanical agitation and by the application of instantly prepared dry chromous chloride. This reaction is useful for the preparation of olefins with base labile functional groups.