Synthesis of Unsaturated Organotrifluoroborates via Wittig and Horner−Wadsworth−Emmons Olefination

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Abstract
The stereoselective synthesis of unsaturated organotrifluoroborates by using the Wittig and Horner−Wadsworth−Emmons olefination is described. These reactions were general for both alkyl- and aryltrifluoroborates. The synthesis of di- and trisubstituted olefins was achieved by using formyl- and acetyl-substituted organotrifluoroborates. The products were isolated in moderate to excellent yield. The Wittig reaction with nonstabilized ylides was performed under salt free conditions in most cases to obtain the Z-isomer. The E-isomer was accessed by using preformed stabilized ylides. The Horner−Wadsworth−Emmons reaction also gave the E-isomer as expected.