Imidazoles 2-acetylene amines

Saczewski and colleagues reported a similar pathway when the A-aryl-A-(4,5-dihydro-l//-imidazol-2-yl)hydroxylamine hydrochlorides 37 were refluxed in acetone in the presence of acetylenic derivatives 38 carrying electron-withdrawing substituents (equation 10). However, when 37 free bases were used, the adducts rearranged at room temperature, producing only the ketene aminals 39 in poor yields (equation 11). 

Reppe has shown that secondary amines of low basicity, such as carbazole, diphenylamine, indole, imidazole, and benzimidazole, and amides such as pyrrolidone react with acetylene in the presence of strong alkali to give vinyl derivatives [81, 83, 84a, b] (Eq. 30). As described by Reppe, these reactions are... 

The scope of direct amination reactions is not too great in comparison with all other methods for synthesizing simple N-aminoimidazoles. Probably the first specific example of N-amination of imidazoles was the synthesis of l-tosylamino-2,4,5-triphenylimidazole on treatment of the lophine anion with tosylazide [Eq. (9)] (72BCJ306). However, the yield of 35 was small because of the side formation of 2,4,6-triphenyl-l,3,5-triazine and diphenyl acetylene. 

Many ring-fused imidazole derivatives have been synthesized by various methods. Domino Michael addition retro-ene reaction of 2-alkoxyiminoimidazolidines and acetylene carboxylates provided a synthesis of 2,3-dihydroimidazo[l,2-a]pyrimidin-5-(l//)-ones <05T5303>. A single step synthesis of 3,5-dialkyl-9-nitroimidazo[l,2-c]quinazolin-2(3//)-ones from simple carbonyl compounds, primary amines or amino acid methyl esters and 2-azido-5-nitrobenzonitrile has been published <05TL5778>. Diels-Alder reaction of azadienes and benzimidazole-4,7-diones afforded imidazo[4,5-g ]quinoline-4,9-dione derivatives <05EJ01903>. Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of 4,5-diphenyl-l,3-dihydro-2//-imidazol-2-one provided a one-pot synthesis of 5//-imidazo[2,l-ft][l,3]oxazine derivatives <05T2645>. Microwave irradiation was employed in the synthesis of 1-ary 1-3-acetyl-1,4,5,6-... 

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