Vinylamines—VIII : The reaction of cyclohexanone enamines with 1- and 2-nitropropene

Abstract

Enamines containing a trisubstituted double bond were obtained by reaction of morpholine, piperidine and pyrrolidine enamines of cyclohexanone with 1-nitropropene. Different results were obtained in the reaction of the same enamines with 2-nitropropene. A cycloaddition reaction occurred between 1-N-morpholino-cyclohexene and 2-nitropropene in ether at 0°, leading to an oxazine derivative. The structures of the products were determined by spectral and chemical evidence. In acetonitrile at 0° or in ether at room temperature the same enamine reacted with 2-nitropropene to give an enaminic mixture, where the less substituted alkylated isomer appeared to be the minor component. Analogous behaviour was shown by piperidine and pyrrolidene enamines. The mechanism and the stereochemistry of these reactions have been discussed. The formation of diadducts of a different nature from morpholine and pyrrolidine enamines with excess 2-nitropropene is also reported.