Direct observation of conjugated bis-ketene and ketene–ketenimine intermediates in the photolysis of diphenylcyclobutenedione derivatives

Abstract

The photolysis of diphenylcyclobutenedion (Ia) and its imine derivative (Ib) in the presence of an isonitrile gives ring-expanded products (IIIa) and (IIIb)via conjugated bis-ketene (IIa) and ketene-ketenimine (IIb) intermediates, which were confirmed by the photolysis of (I) in methanol to give succinate (IV) and directyl by i.r. spectroscopy during low temperature photolysis.