N1C2C(=CC=CC=2)C=N1.Br[C:11]1[CH:24]=[CH:23][C:14]2[C:15]([C:18]([O:20][CH2:21][CH3:22])=[O:19])=[N:16][O:17][C:13]=2[CH:12]=1.BrC1C=CC(Br)=CC=1[N+]([O-])=O.C(OCC)(=O)CC(OCC)=O.C(ON=O)CC(C)C>>[O:17]1[C:13]2[CH:12]=[CH:11][CH:24]=[CH:23][C:14]=2[CH:15]=[N:16]1.[O:17]1[C:13]2[CH:12]=[CH:11][CH:24]=[CH:23][C:14]=2[C:15]([C:18]([O:20][CH2:21][CH3:22])=[O:19])=[N:16]1The benzisoxazole-, benzisoxazole-, and benzothiazolecarboxylic acids were prepared using similar strategies outlined for the indazole acids. For example, ethyl 6-bromobenzisoxazole-3-carboxylate was prepared from 2,5-dibromonitrobenzene by reaction with diethyl malonate, saponification and decarboxylation, and reaction with isoamylnitrite. Ethyl benzisoxazole-3-carboxylate was obtained by hydrogenolysis of the 6-bromo derivative. 4-Benzothiazolecarboxylic acid was prepared from 2-amino-4-chloro-benzothiazole by reaction with isoamyl nitrite followed by metal-halogen exchange and trapping with carbon dioxide. 5-Benzothiazolecarboxylic acid was prepared from 4-chloro-3-nitrobenzoic acid by reaction with Na2S and sodium hydroxide followed by reduction with zinc in formic acid. 3-Benzisothiazolecarboxylic acid was prepared from thiophenol by reaction with oxalyl chloride and aluminum chloride followed by treatment with hydroxylamine, hydrogen peroxide, and sodium hydroxide.
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