Rhombic Cyclobutadiene with a Boryl/Amino-Substitution Pattern: Boryl Group Migration Induced by Reaction with Water

The synthesis of a donor-acceptor cyclobutadiene featuring a boryl/amino-substitution pattern is presented together with its characteristic reactivity toward water. On the basis of the results of X-ray crystallography, theoretical studies, and spectroscopic analyses, the observed rhombic structure of the cyclobutadiene was attributed to a charge-separated electronic structure. Reaction of this boryl-substituted cyclobutadiene with water induced a characteristic migration of the boryl group, due to the Lewis acidity of the boryl-substituent