Gas-phase rearrangement and cyclisation reactions of 2-benzylphenylaminyl radicals and related 2-hetero-analogues

Abstract

Gas-phase pyrolysis of the appropriate N-allyl or N-benzyl compound leads to the aminyl radicals 1(X = NH, Y = CH₂, CO, S, or O). Equilibration of these via the spirodienyl 2 gives mixtures of isomeric acridans or acridones as major products from radicals 1(X = NH, Y = CH₂ and Y = CO, respectively) and isomeric phenothiazines as minor products from radical 1(X = NH, Y = S). The major product in this case is the aminodibenzofuran 29 which may be formed by H-abstraction by the aminyl to give an aryl radical, followed by cyclisation (Scheme 6). The only cyclised product from radical 1(X = NH, Y = O) is the carbazole 35, formed by a mechanism similar to that of Scheme 6, but in which H-abstraction by the rearranged phenoxyl radical has taken place.