Über den sterischen Verlauf der Umsetzung von Enaminen aus offenkettigen Aldehyden und Ketonen mit Nitroolefinen zu 2,3‐disubstituierten 4‐Nitroketonen

On the Steric Course of the Reaction of Enamines Derived from Open‐Chain Aldehydes and Ketones with Nitro‐olefins Yielding 2,3‐Disubstituted 4‐Nitroketones The relative configuration of the nitro‐ketone 12 obtained by the title reaction has been proved by a Baeyer‐Villiger degradation and subsequent reduction to the amino‐alcohol (±)‐(u)‐20, the relative configuration of which is identical with a sample prepared from 2‐methyl‐3‐hydroxybutyrate of known configuration (Scheme 1). The stereochemical course of the title reaction is thus as predicted by our topological rule. It is assumed that the other nitro‐ketones 13–18 described here are also formed by (lk)‐combination of the trigonal centers of the educts (diastereoselectivity > 90%, see Formulae and Fig. 1). It is not possible to reverse this relative topicity by employing (Z)‐ instead of (E)‐components of the starting materials, due to the reversibility of the primary step of these Michael additions (Schemes 2 and 3, and Fig. 2).