Synthesis of a diboryl-N-heterocycle and its conversion to a bidentate cationic Lewis acid

Abstract

Sequential reaction of 2-lithio-1-methylimidazole with 9-borabicyclo[3.3.1]nonane (9-BBN) dimer and 9-Cl-9-BBN yields diboryl-N-heterocycle C₄H₅N₂(H)(BC₈H₁₄)₂ (1). Reaction of 1 with I₂ results in the net substitution of chelated hydride for a singly boron-bound iodide to produce C₄H₅N₂(I)(BC₈H₁₄)₂ (2). Conversely, reaction of 1 with [Ph₃C][B(C₆F₅)₄] results in the formation of the bidentate cationic Lewis acid [(C₄H₅N₂)(BC₈H₁₄)₂][B(C₆F₅)₄] (3). Compound 3 catalyzes the hydrogenation of N-benzylidene-tert-butylamine at room-temperature.