Substitution at sp boron of a six-membered NHC·BH: 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 ). 6-SIDipp·BH 3 ( 1 ) was reacted with I 2 to give corresponding iodoboranes ( 2 & 3 ), which underwent nucleophilic substitution reactions to furnish OTf and ONO 2 substituted boranes ( 4-7 ). Treatment of Br 2 /H 2 O with 1 led to a dihydroxyborenium cation ( 8 ).