Sterically hindered aromatic compounds. VII. Deoxygenation of 2,5-di-tert-butyl- and 2,4,6-tri-tert-butylnitrosobenzene

Deoxygenation of 2,5-di-tert-butylnitrosobenzene (1) by triethylphosphite gave a complex mixture containing 2,5-di-tert-butylaniline, 2,5,2′,5′-tetra-tert-butylazobenzene, N-(2,5-di-tert-butylphenyl)-α-tert-butyl-α-2-(5-tert-butylpyridyl)nitrone, and diethyl N-(2,5-di-tert-butylphenyl)phosphoramidate. In contrast deoxygenation of 2,4,6-tri-tert-butylnitrosobenzene (2) yielded mainly 3,3-dimethyl-5,7-di-tert-butyl-2,3-dihydroindole (80%), together with small amounts of 2,4,6-tri-tert-butylaniline and a product of side chain rearrangement, 2-(2-methyl-3-propenyl)-4,6-di-tert-butylaniline. Reaction pathways involving nitrenoid intermediates account for the various products. The different types of products from 1 and 2 are explained in terms of differential steric and conformational effects.