Synthesis and properties of 1,2-diaryl-4,5,6,7-tetrahydro-1H-1,3-diazepines and 1,2-diaryl-1,4,5,6,7,8-hexahydro-1,3-diazocines. Comparison with the five- and six-membered homologues

Abstract

The cyclization of N-aroyl-N′-aryl-tetra- and -penta-methylenediamines with ethyl polyphosphate afforded 1,2-diaryl derivatives of 4,5,6,7-tetrahydro-1H-1,3-diazepines and 1,4,5,6,7,8-hexahydro-1,3-diazocines respectively. To compare the basicity of these compounds with that of the five- and six-membered homologues, their pK_a values were determined. The pK_a values decrease in the order: tetrahydropyrimidines > tetrahydrodiazepines > hexahydrodiazocines > imidazolines. Rate constants for the hydrolysis of a series of homologues were determined in boiling alkaline 95% ethanol. It was observed that stability to alkaline hydrolysis increases in the order: imidazolines < tetrahydropyrimidines tetrahydrodiazepines < hexahydrodiazocines. With these and other data, some conformational aspects were analysed.