Metal‐Mediated Synthesis of 1,4‐Di‐tert‐butyl‐1,4‐azaborine

Completing the set: Although 1,2-azaborine is known, little is known about the 1,3- and 1,4-analogues. Now a simple, controlled synthesis of 1,2-di-tert-butyl-1,2-azaborine from acetylene and di-tert-butyliminoborane has been achieved by a metal-mediated formal [2+2+2] cycloaddition reaction. A 1,2-azaborete pianostool complex was identified as an reaction intermediate.