Reactions of 3-(2-Methyl-1,3-dioxolan-2-yl)tropolone Methyl Ethers with Hydrazines, Thiourea, Guanidine, and Amidines

3-(2-Methyl-1,3-dioxolan-2-yl)tropolone, prepared from 3-acetyltropolone, was methylated with diazomethane to afford 2-methoxy-3-(2-methyl-1,3-dioxolan-2-yl)tropone (3a) and 2-methoxy-7-(2-methyl-1,3-dioxolan-2-yl)tropone (3b). The methyl ether 3a reacted with hydrazine to afford 2-hydrazono-3-(2-methyl-1,3-dioxolan-2-yl)-3,5-cycloheptadien-1-one and 3-methyl-1,8-dihydrocycloheptapyrazol-8-one. The reaction with methylhydrazine afforded 3-(2-methyl-1,3-dioxolan-2-yl)-2-methylhydrazono-3,5-cycloheptadien-1-one and 1,3-and 2,3-dimethyl-dihydrocycloheptapyrazol-8-ones. Another methyl ether 3b reacted with hydrazine to afford 2-hydrazino-7-(2-methyl-1,3-dioxolan-2-yl)tropone, while the reaction with methylhydrazine gave 2-(2-methyl-1,3-dioxolan-2-yl)-7-(2-methylhydrazino)tropone, 2-(2-methyl-1,3-dioxolan-2-yl)-7-(1-methylhydrazino)tropone, and 1,3-dimethyl-8-methylhydrazono-1,8-dihydrocycloheptapyrazole. On the other hand, the methyl ether 3a reacted with guanidine, acetamidine, and benzamidine to give 4-(2-methyl-1,3-dioxolan-2-yl)-2-amino-, 2-methyl-, and 2-phenylcycloheptimidazole, respectively. The reaction of the methyl ether 3b also gave the same products. The reaction of 3b with thiourea afforded 2-mercapto-4-(2-methyl-1,3-dioxolan-2-yl)cycloheptimidazole but 3a resulted in the rearrangement to ethyl 2-(2-methyl-1,3-dioxolan-2-yl)benzoate.