With Methide Alkylidene Side Chain

This reaction makes use of the addition of an amino group across a 1,3-enone system in the parent ring. A link with the previous section is furnished by 2-hydroxymethylenecyclohexanone (40), a tautomer of 2-formylcyclo-hexanone. When refluxed with guanidine carbonate in ethanol, it gave a 

Kawamura, R. Tachikawa, and T. Miyadera, Chem. Pharm. Bull. 

2-(l-Ethoxyethylidene)indandione (41) and formamidine, in methanolic sodium methoxide at room temperature, gave a good yield of 4-methylin-deno[l,2-d]pyrimidin-5-one (42). Similarly, acetamidine, guanidine, and methylisothiourea furnished the 2-methyl, 2-amino, and 2-methylthio derivatives, respectively. Urea and thiourea failed to react.30 

j8-unsaturated ketonic structure of the parent is even clearer in the next two examples. 2-Isopropylidenecyclohexanone (43), when heated at 80°C with guanidine, gave an excellent yield of 2-imino-4,4-dimethyl-3,4,5,6,7,8-hexahydroquinazoline (44). With ammonium thiocyanate in boiling toluene and with urea at 40°C in a current of hydrogen chloride gas, good yields of the corresponding 2-thione and 2-one, respectively, were obtained. Similarly, 2-acetyl-l-methylcyclohexanone and ammonium thiocyanate provided a moderate yield of 4,8a-dimethyl-3,4,5,6,7,8,8a-hexa-hydroquinazoline-2-thione (45).31 

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