A Useful Methylene Unit Usable for Suzuki-Miyaura Cross-coupling

Bis(pinacolatoboryl)methane (1) consists of a methylene group and two pinacolatoboryl groups, and can be used for introducing two different functional groups continuously by the use of a palladium catalyst. For example, in the presence of bis(tri-tert-butylphosphine)palladium(0) and potassium hydroxide, 1 reacts with aryl halides at room temperature to afford the desired benzylboronates selectively. In this reaction, sp³-carbon and sp³-carbon forming reactions successfully proceed by use of allyl bromides and benzyl bromides.^1-3) Also, when 1 reacts with aryl halides in two parts, symmetrical diarylmethanes are given. If two different aryl halides react with 1 in order, asymmetrical diarylmethanes are synthesized in one pot.⁴⁾ Furthermore, deprotonation of a methylene proton of 1 can occur by the treatment of LiTMP, and a consequent reaction with alkyl halides affords alkylated diborylmethanes. The given products are applied to the asymmetric Suzuki-Miyaura cross-coupling by use of chiral ligands.⁵⁾