A New Synthesis of Cyclic Ureas, Cyclic Urethanes, and a Quinazolinedione. Selenium-Assisted Carbonylation of Aromatic Amines with Carbon Monoxide

Abstract

Five-, six-, and seven-membered cyclic ureas were synthesized in excellent yields from various aromatic diamines by reaction with carbon monoxide and a stoichiometric or excess amount of selenium in the presence of N-methylpyrrolidine. The carbonylation also proceeded using a catalytic amount of selenium in the presence of an oxidizing agent such as oxygen or dimethyl sulfoxide producing selectively the five and six-membered cyclic ureas. In the case of 2-(2-aminoethyl)aniline under the catalytic conditions, intra- and intermolecular carbonylation competed resulting in the formation of a mixture of the seven-membered cyclic urea, 1,3,4,5-tetrahydro-2H-1,3-benzodiazepin-2-one and the acyclic urea, 1,3-bis[2-(2-aminophenyl)ethyl]urea. The distribution ratio of these two products varied depending on the reaction conditions, but selective formation of the cyclic urea was attained only when a stoichiometric or excess amount of selenium was used. In addition to the above diamino compounds, 2-carbamoylaniline, 2-amino-3-pyridinol, and 2-(hydroxymethyl)aniline also underwent similar carbonylation to give 2,4(1H,3H)-quinazolinedione, oxazolo[4,5-b]pyridin-2-(3H)-one, and 1,4-dihydro-2H-3,1-benzoxazin-2-one, respectively.