Thermal induced intramolecular [2 + 2] cycloaddition of allene-ACPs

A facile synthetic method for preparation of bicyclo[4.2.0] nitrogen heterocycles has been developed via a thermal induced intramolecular [2 + 2] cycloaddition reaction of allene-ACPs. The DFT calculations indicate that this intramolecular cycloaddition proceeds in a concerted manner and a strained small ring is essential.