[CH3:1][C:2]1[O:3][C:4]2[C:10]3=[C:11]([S:17][CH3:18])[S:12][C:13]([C:14](O)=[O:15])=[C:9]3[CH2:8][CH2:7][C:5]=2[N:6]=1.C(Cl)(=O)C(Cl)=O.C[N:26](C)C=O>O1CCCC1>[CH3:1][C:2]1[O:3][C:4]2[C:10]3=[C:11]([S:17][CH3:18])[S:12][C:13]([C:14]([NH2:26])=[O:15])=[C:9]3[CH2:8][CH2:7][C:5]=2[N:6]=14,5-Dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxylic acid (0.47 g) was suspended in tetrahydrofuran (15 ml); oxalyl chloride (0.32 g) and then N,N-dimethylformamide (6 μl) were added. After this mixture was stirred at room temperature for 2 hours, it was concentrated under reduced pressure. The residue was suspended in tetrahydrofuran (5 ml) and cooled with ice; concentrated aqueous ammonia (4.0 ml) was added. After the reaction mixture was stirred at room temperature for 1 hour, it was poured over water (150 ml) and extracted with ethyl acetate-tetrahydrofuran (3:1, v/v). The organic layer was washed with water and dried (MgSO4), after which the solvent was distilled off to yield 4,5-dihydro-2-methyl-8-methylthiothieno[3,4-g]benzoxazole-6-carboxamide (0.27 g, 57%), which was then recrystallized from chloroform-methanol. Light-yellow needles. Melting point over 300° C.
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