Unprecedented Borylene Insertion into a C–N Bond

Abstract

Abstract Carbenes are well established reactive intermediates and play an important role in organic synthesis, whereas the scope of borylenes is rather limited. Selective borylene insertion into a C–N bond to yield boryl‐functionalized N‐heterocyclic olefins (NHOs), [{N(Dipp)N(DippBH)CHCH}CCH 2 ] 2 ( 6 ) and [{N(Dipp)N(DippBPh)CHCH}CCH 2 ][{N(Dipp)N(2‐ i Pr‐6‐CHMeCH 2 BC 6 H 3 )CHCH}CCH 2 ] ( 8 ) (Dipp = 2,6‐ i Pr 2 C 6 H 3 ) is reported for the first time. KC 8 reduction of (IPrCH 2 )BRX 2 adducts (IPrCH 2 = {N(Dipp)CH} 2 CCH 2 ; R = X = I ( 2 ); R = Ph, X = Cl ( 4 )) affords compounds 6 and 8 . Surprisingly, treatment of (IPrCH 2 )BHCl 2 ( 3 ) with KC 8 yields completely unexpected diborane compound (IPr)BH 2 BH 2 (IPr) ( 7 ). Compound 2 is unstable in THF and induces ring opening reaction to form the borenium ion [(IPrCH 2 )B{O(CH 2 ) 4 I} 2 ]I ( 5 ).