反应详情

The second starting material used to prepared those compounds in which the benzoxazole ring is formed first is a substituted-3-chloroaniline (STM2). The aniline (STM2) is reacted with the appropriate alkyl anhydride, for example trimethylacetic anhydride, under acidic conditions, yielding the corresponding N-(substituted-3-chlorophenyl)alkylamide (B-1). The aniline (STM2) can also be reacted with the appropriate propanoic acid (A-2), for example 2-methoxy-2-methylpropanoic acid, under basic conditions to form the appropriate N-(substituted-3-chlorophenyl)-substituted-alkylpropion-amide (B-2), for example N-(3-chloro-4-fluorophenyl)-2-methoxy-2-methyl-propionamide. The amides (B-1 or B-2) are in turn treated with n-butyl-lithium and cyclized with solid carbon dioxide, affording the corresponding [2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]carboxylic acid (C), for example, (2-t-butyl-6-fluorobenzoxazol-7-yl)carboxylic acid. The so-prepared carboxylic acid (C) is then reacted with ethyl chloroformate, 4-methylmorpholine, and sodium azide, yielding the corresponding [2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]carbonyl azide (C-1), which is treated with ethanol to form the corresponding ethyl N-[2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]carbamate (D). Additional substituents may optionally be added to the benzoxazole ring at this point. For example, ethyl N-(2-t-butyl-6-fluorobenzoxazol-7-yl)carbamate (D) is treated with N,N-dichlorourethane under acidic conditions, affording ethyl N-(2-t-butyl-4-chloro-6-fluorobenzoxazol-7-yl)carbamate (E). The carbamates D and E are then reacted with ethyl 3-amino-4,4,4-trifluorocrotonate, sodium methoxide, and DBU to form the corresponding 3-[2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]-6-trifluoromethyl-2,4-(1H,3H)-pyrimidine-dione (F). The pyrimidinedione (F) is further reacted under basic conditions with an alkyl halide, for example methyl iodide, or O-(2,4-dinitrophenyl)hydroxylamine, or 1-aminooxysulfonyl-2,4,6-trimethylbenzene, affording the targeted 3-[2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]-1-alkyl-6-trifluoromethyl-2,4-(1H,3H)-pyrimidinedione (I) or 3-[2-alkyl- or 2-(substituted-alkyl)-substituted-benzoxazol-7-yl]-1-amino-6-trifluoromethyl-2,4-(1H,3H)-pyrimidinedione (II). Examples 1, 2, 4, and 5 provide the detailed procedures for this route.

1. additionAdditional substituents may optionally be added to the benzoxazole ring at this point