Ethyl propiolate → HCID 178472242, compound

Participants

Reaction Steps

Scheme 10 shows the synthesis of 9-bromo-2-(1-isopropyl-3-methyl-1H-1,2,4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepine III from 4-bromo-2-fluorobenzonitrile 11. Addition of hydroxylamine to the nitrile of 11 gave 4-bromo-2-fluoro-N-hydroxybenzimidamide 24. Michael addition of 24 to ethyl propiolate gave ethyl 3-(4-bromo-2-fluorobenzimidamidooxy)acrylate 25. Heating 25 in a high-boiling solvent such as toluene, xylene, ethylbenzene, or diphenyl oxide gave cyclized imidazole, ethyl 2-(4-bromo-2-fluorophenyl)-1H-imidazole-4-carboxylate 26, along with by-product pyrimidine, 2-(4-bromo-2-fluorophenyl)pyrimidin-4-ol. Alternatively, 25 can be cyclized to 26 with catalytic Lewis acids such as Cu(I) or Cu(II) salts. Alkylation of 26 with a 2-hydroxyethylation reagent, such as 1,3-dioxolan-2-one, in a base, such as N-methylimidazole or cesium carbonate, gave ethyl 2-(4-bromo-2-fluorophenyl)-1-(2-hydroxyethyl)-1H-imidazole-4-carboxylate 27. Ring-cyclization of 27 with an aqueous basic reagent, such as potassium hydroxide, lithium hydroxide, and methyl tributylammonium hydrochloride, gave 9-bromo-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepine-2-carboxylic acid 28. Addition of acetamidine to 28 with triphenylphosphine gave 9-bromo-N-(1-iminoethyl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepine-2-carboxamide 29. Ring-cyclization of 29 with isopropylhydrazine hydrochloride 4 in acetic acid gave 9-bromo-2-(1-isopropyl-3-methyl-1H-1,2,4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepine III.

Provenance & Evidence