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An efficient regioselective cross-coupling reactions of tert-butyl 2,4-dibrominated-5-methyl-1H-imidazole-1-carboxylate is reported. This new synthetic route runs under simple and mild conditions and selectively gives an easy access to 2,4-dialkynylated and 2-alkynylated-4-arylated-1H-imidazole-1-carboxylate in good to excellent yields.

A series of 2,7-disubstituted 3-methylimidazo[1,2-c][1,3]oxazin-5-one were synthesized in good yields via Ag2CO3/TFA-mediated an intramolecular annulation of N-Boc-2-alkynyl-4-bromo(alkynyl)-5-methylimidazoles. This methodology was carried out in the presence of a catalytic amount of...

A small library of 1H-benzo[4,5]imidazo[1,2-c][1,3]oxazin-1-one derivatives was prepared in good to excellent yields, involving a Ag2CO3/TFA-catalyzed intramolecular oxacyclization of N-Boc-2-alkynylbenzimidazole substrates. In all experiments, the 6-endo-dig cyclization was exclusively achieved since the possible 5-exo-dig heterocycle was not observed, indicating the high regioselectivity of this process. The scope and limitations of the silver catalyzed 6-endo-dig cyclization of N-Boc-2-alkynylbenzimidazoles as substrates, bearing various substituents, were investigated. While ZnCl2 has shown limits for alkynes with an aromatic substituent, Ag2CO3/TFA demonstrated its effectiveness and compatibility regardless of the nature of the starting alkyne (aliphatic, aromatic or heteroaromatic), providing a practical regioselective access to structurally diverse 1H-benzo[4,5]imidazo[1,2-c][1,3]oxazin-1-ones in good yields. Moreover, the rationalization of oxacyclization selectivity in favor of 6-endo-dig over 5-exo-dig was explained by a complementary computational study.

An efficient one-pot regioselective synthesis of 2-(1,2,3-triazolyl)methyl-3-alkynyl imidazo[1,2-a]pyridines is reported under simple and mild reaction conditions. The new imidazo[1,2-a] pyridines embedded with 4-substituted-[1,2,3]-triazole were obtained in good to excellent yields from 2-(chloromethyl)-3iodo imidazo[1,2-a]pyridines via a one-pot sequence involving an SN reaction with azide, followed by copper-catalyzed [3 + 2] cycloaddition and a Sonogashira coupling reaction.