Synthetic application of α-hydroxydiazene systems. II. Uncatalyzed and phenol catalyzed radical chain hydro-tert-butylation of unsaturated compounds with tert-butylazodiphenylcarbinol

tert-Butylazodiphenylcarbinol 1 decomposes in benzene solution by a chain mechanism involving tert-butyl radicals. Many olefinic compounds and azobenzene act as radical traps and are hydro-tert-butylated by 1 . The regiochemistry of hydro-tert-butylation of unsymmetric alkenes is that expected for a mechanism which involves addition of tert-butyl radical so as to form the most stable radical adduct, which subsequently abstracts hydrogen from 1 .In some cases phenol acts as a catalyst for the hydroalkylation process. The novel catalytic effect of phenol in a radical chain process is attributed to the favourable thermochemistry for induced, concerted decomposition of 1 by radical attack at hydroxyl hydrogen.