REARRANGEMENTS OF AZIDOQUINONES - GENERATION OF A BENZYNE INTERMEDIATE

Reported here is a rearrangement envisaged to involve the unique generation of a benzyne intermediate from anazidoquinone precursor.1Specifically, 3-azido-6-chloro-5-ethoxy-4-[(trimethylsilyl)ethynyl]-l,2-benzoquinone (4) was prepared as outlined in Scheme I (1 → 2 → 3 → 4) and subjected to thermolysis in refluxing benzene; the bicyclic compound 7 was thus obtained in 38% isolated yield.2 This unusual transformation is considered to proceed via the diradical intermediate 5, which suffers a trimethylsilyl shift from carbon to oxygen to give the benzyne 6. This then undergoes a Diels-Alder cycloaddition to the solvent resulting in adduct 7. © 1990, American Chemical Society. All rights reserved.