Gold-catalyzed synthesis of dibenzo[1,5]diazocines from β-(2-aminophenyl)-α,β-ynones

beta-(2-Aminophenyl)-alpha,beta-ynones afforded exclusively challenging dibenzo[1,5]diazocines by means of (JonPhosAuNCMe)SbF6 catalysis. In contrast with the known gold-catalyzed reaction path of 2-alkynylanilines that leads to indoles, ynones underwent an auto intermolecular hydroamination. This process resulted finally in the formation of an eight-membered ring, likely through a selective 8-exo-dig intramolecular hydroamination that prevailed over the possible cyclocondensation reaction (that would result in the formation of 4-aminoquinoline derivatives). The easy availability of beta-(2-aminophenyl)-alpha,beta-ynones and the simple cyclization procedure make this approach suitable for the preparation of a wide range of useful dibenzodiazocines. The methodology can be extended to the use of beta-(2-aminophenyl)-alpha,beta-ynoates as substrates.