Cross-Nucleophile coupling: synthesis of a new C-C bond between alkylboranes and boronates

Abstract

Many general methods are now available for the cross-coupling of carbon nucleophiles with carbon electrophiles, and even the couplings between two electrophiles have been gradually developed in the last decade. There remain problems with the synthesis of these electrophiles and their toxicity is not negligible. Reactions that directly couple two carbon nucleophiles, "cross-nucleophiles coupling reactions," avoid this challenge, but these reactions have not been extensively developed. Herein we reported a new method for cross-nucleophile coupling utilizing copper catalyst with NHC ligands to synthesize a new C-C bond between alkylboranes and boronates. This new reaction tolerates a variety of functional groups, which can be accomplished in the presence of esters, nitriles, aryl bromides, ethers, alkyl chlorides, anilines, and a wide range of nitrogen-containing heteroaromatic compounds. We propose that the the reaction is realized through the transmetallation competition of the borates over boranes. Hydrogen gas was observed during the reaction, and it is hypothesized to be formed through the presence of a copper hydride.