Synthesis of 3-Amino-1,4-dihydropyridine Derivative via an Intramolecular Rearrangement of 1,4-Dihydropyridine-3-hydroxamate

2,6-Dimethyl-4-(3'-nitrophenyl)-3-methoxylaminocarbonyl-1,4-dihydropyridine-5-carboxylic acid methylester, 3b reacted with 2-cyanoethanol or benzylalcohol to give the corresponding cyanoethylurethane compound 6c in 40.6% yield and benzylurethane compound 6d in 32% yield. The cyanoethylurethane 6c was hydrolized in ethanolic NaOH to give 2,6-dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3-amino-5-carboxylic acid 5-methyl ester. HCl 8 in 64.8% yield. Another acid hydrolysis of benzylurethane 6d gave 2,6-dimethyl-4-(3'-nitrophenyl)-1,4-dihydropyridine-3-amino-5-carboxylic acid 5-methylester. HBr 11 in 54.7% yield.