Substitution at sp 3 boron of a six-membered NHC·BH 3 : convenient access to a dihydroxyborenium cation.

Herein, we have undertaken the synthesis and investigated the reactivity of a 6-membered saturated NHC borane adduct (1). Direct electrophilic halogenation of 1 with a stoichiometric amount of I 2 led to NHC boryl iodides, 6-SIDipp·BH 2 I (2) and 6-SIDipp·BHI 2 (3), which were further reacted with various nucleophiles to give novel 6-SIDipp based mono and disubstituted boranes with OTf (4 and 6) or ONO 2 (5 and 7) functional groups. The addition of Br 2 /H 2 O to 1 smoothly results in a dihydroxyborenium cation (8).