α‐Chlor‐nitrone I: Darstellung und Ag+‐induzierte Reaktion mit Olefinen. Über synthetische Methoden, 5. (vorläufige) Mitteilung

Organic synthesis may be said to be in need of enophiles, i.e. reagents that would undergo cycloaddition reactions with any isolated olefinic double bond, in contrast to most of the classical Diels‐Alder or 1,3‐dipolar addition reagents which, as a rule, require activated olefins in order to participate smoothly in cycloaddition processes. This paper introduces α‐chloronitrones as precursors of a new class of such reagents; they undergo an Ag+‐induced reaction with unactivated olefins with great ease to give products considered to result from 1,4‐cycloadditions of N‐alkyl‐N‐vinyl‐nitrosonium ions to the carbon‐carbon double bond (see scheme 2). This process is believed to have a number of synthetic applications, two of them being illustrated in two subsequent communications.