Three-membered rings, acyl, conformation

In view of this conformational behavior and of the generally accepted properties of three-membered rings to conjugate with unsaturated groups, it seems more appropriate to consider acyl derivatives of these rings in the context of conjugated carbonyl heterocycles than in that of derivatives of saturated carbon. 

In C- and N-acyl derivatives of three-membered rings, the geometry of the conformers still seems rather undetermined and, as a result, the same may be said of conformer populations. This is true of simple acetyl derivatives and, of course, of the conformationally more complex aroyl derivatives. For the N-acylaziridines, assignment of nitrogen invertomers seems sufficiently reliable... 

C-Acyl and N-acyl derivatives of three-membered rings have received little attention in recent investigations, especially with regard to up-to-date experimental techniques for determining dynamic and structural parameters of the conformational equilibrium. 

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