“…Boracyclopropene, or borirene, is isoelectronic with the cyclopropenylium cation and, as such, represents the simplest boron‐containing cyclic system that might exhibit 2π aromatic stabilization 1. A limited number of synthetic routes have been successfully applied to the generation of the borirene nucleus 2–5. Among these, only two methods, although restricted in scope, yielded satisfactory amounts of the desired compounds: 1) the reaction reported by Pues and Berndt3 of trimethylstannylalkynes with 1,2‐di‐ tert ‐butyl‐1,2‐dichlorodiborane(4) which affords 1‐ tert ‐butylborirenes, and 2) the photoisomerization of diaryl(arylethynyl)boranes reported by Eisch et al5 The latter method, in particular, allowed the isolation and structural characterization of 2‐(2,6‐dimethylphenyl)‐1,3‐dimesitylborirene ( 1 ), thus providing experimental evidence for the theoretically predicted aromaticity of this class of compounds.…”