Aryl-Csp~3Bond Rotation Barriers of 2-ArylPerhydropyrrolo[3,4-c]pyrrole-1,3-diones

摘要

The static and dynamic features of 2-aryl perhydropyrrolo[3,4-c]pyrrole-1,3-diones bearing N-acylsubstituents have been assessed with the aid of crystal structures and VT NMR spectra. Rotationbarriers for the aryl-Csp~3bonds in these molecules show surprising variation. Amide-substitutedderivatives and fused piperazinediones (six-membered fusion) exhibit very substantial barriers of14-15 kcal/mol. Fused benzodiazepinediones (seven-membered fusion) have lower but still significantbarriers (10 kcal/mol), while fused hydantoins (five-membered fusion) have barriers that are too low tomeasure by VT NMR(≤10 kcal/mol). A rationale for the origin of the barriers is presented.