일 시 : 2011년 10월 27일, 오후 5:00
장 소 : 500동 목암홀

-Abstract-
   Silver-mediated intermolecular amination reactions of benzoxazoles were developed using formamides or parent amines as an amino group source. While the reaction with formamides requires rather harsh conditions, that with parent amines proceeds under milder conditions to afford 2-aminobenzoxazoles in high yields. A catalytic method of employing cobalt- or manganese species has been developed using peroxide and acid additive to couple various types of azoles with ammonia, primary and secondary amines.
New synthetic procedures of intramolecular oxidative C−N bond formation have been developed for the preparation of carbazoles starting from N-substituted amidobiphenyls under either copper-catalyzed or metal-free conditions using hypervalent iodine(III) as an oxidant. Whereas iodobenzene diacetate or bis(trifluoroacetoxy)iodobenzene alone performs the reaction to provide carbazole products in moderate to low yields, a combined use of copper(II) triflate and the iodine(III) species significantly improves the reaction efficiency, allowing a more diverse range of products to obtain in good to excellent yields. On the basis of mechanistic studies, the role of copper species is proposed to catalytically activate the hypervalent iodine(III) oxidants. A synthetic utility of the present approach was nicely demonstrated in a direct synthesis of indolo[3,2-b]carbazole utilizing a double C−N bond formation.