Thermal elimination reactions of nitrones. Part 1. Applications, limitations, and stereochemistry

Abstract

A series of N-(fluoren-9-ylidene)alkylamine N-oxides has been synthesised by direct oxidation of the parent imines with peroxy-acid. Most of these nitrones underwent a thermal elimination reaction (analogous to the Cope elimination of tertiary amine oxides) to produce olefin and oxime products. The elimination reaction was followed by g.l.c. and mass and n.m.r. spectroscopic techniques, and the results are rationalised in terms of several factors including statistical and steric effects and olefin stability. The applications and limitations of this nitrone elimination reaction and the relationship between the stereochemistry of reactants and that of products has been examined for various nitrones R¹R²CN⁺(O^–)R³(R¹= aryl, R²= H; R¹ and R² both alkyl; R¹= alkyl, R²= aryl; R¹ and R² both aryl).