Synthesis and Properties of 2,4,6‐Trimethylphenylborane (Mesitylborane), a Stable Alternative to Thexylborane

Four advantageous properties characterize mesitylborane MesBH 2 as a reagent: (1) It is readily accessible and quite stable. (2) It can be treated with two different 1‐alkenes in a stepwise fashion (→ MesBR 1 R 2 ). (3) The regioselectivity of each individual step is > 99%. (4) The products MesBR 1 R 2 can be readily transformed via MeOBR 1 R 2 or directly to BR 1 R 2 R 3 . MesBR 2 and BR 1 R 2 R 3 are important precursors for the synthesis of ketones R 1 R 2 CO and tertiary alcohols R 1 R 2 R 3 COH, respectively, by the cyanoborate process.