In the context of our longstanding interest in subvalent boron compounds, we targeted the liberation of a carbene-stabilized borylene from a suitable organoboron precursor. For this purpose, we tested 7-borabicyclo [2.2. 1] hepta-2, 5-dienes (or 7-boranorbornadienes in short) obtained from facile [4+ 2] cycloaddition of boroles and alkynes. By formation of a Lewis adduct with an N-heterocyclic carbene (NHC), we intended to block previously ...