The photoaddition of aliphatic amines to benzene

Abstract

Primary, secondary, and tertiary aliphatic amines undergo photoaddition to benzene via photoexcitation of benzene to the S₁ state. Primary amines give products of 1,2-, 1,3-, and 1,4-addition of the N–H bond, although the 1,3-adducts are derived from secondary photoreactions of the 1,2-adducts by way of hexa-1,3,5-triene intermediates. Secondary amines react similarly, but give only 1,2- and 1,4-adducts. The photoadditions of tertiary amines involve an α-C–H bond in the amine and occur 1,4- to the benzene ring, but little addition occurs in the absence of methanol or other proton donors. The mechanisms of these reactions have been investigated, and the findings are discussed : charge-transfer processes and both polar and radical intermediates appear to be involved.