Suzuki-Miyaura cross-coupling reactions of alkylboronic acid derivatives or alkyltrifluoroborates with aryl, alkenyl or alkyl halides and triflates

Palladium-catalysed Suzuki-Miyaura cross-couplings of organoboronic acids or organotrifluoroborates with aryl and alkenyl halides or triflates have become classic methods for generating carbon-carbon bonds. For this reaction, not only sp(2)-hybridized but also sp(3)-hybridized organoboron derivatives can be employed. However, alkylboronic acids or trifluoroborates are generally less reactive than arylboron derivatives. The coupling of primary alkylboronic acids or alkyltrifluoroborates with aryl or alkenyl halides is well known, and the reaction gives the coupling products with high selectivities, relatively high turnover numbers and in good yields with several catalysts. On the other hand, secondary alkylboronic acids or trifluoroborates, except for cyclopropylboron derivatives, are much less reactive, and very few catalyst are able to activate such compounds. Because of the hybridization of cyclopropanes, which confers significant aromatic character, several reactions have successfully been performed with cyclopropylboronic acids or trifluoroborates. The stereochernistries of substituted cyclopropylboron derivatives were maintained in the course of the reactions. For all these couplings with primary or secondary alkylboron derivatives, aryl iodides, bromides, chlorides or triflates and alkenyl iodides, bromides or triflates were employed. Alkenyl chlorides have attracted less attention. The reactions with alkenyl halides are stereos elective. A few examples of couplings between sp(3)-hybridized organoboronic acids and alkyl halides have also been reported. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).