Diethyl ketone may be reacted with methyl nitrite and that product in turn reacted with cyclohexan-1,3-dione to give 3-ethyl-4,5,6,7-tetrahydro-2-
methyl-4-oxoindole.
3-ethyl-4,5,6,7-tetrahydro-2-methyl-4-oxoindole 14.1 g (0.08 mol), 14.8 g
morpholine hydrochloride (0.12 mol), and 3.6 g paraformaldehyde (0.12 mol)
were refluxed in 200 ml ethanol for 40 hours. The solution was evaporated to
dryness in vacuo on a steam bath and the residue digested with a mixture of
150 ml water and 10 ml 2N HCl. An insoluble residue of unreacted starting
material was filtered off. To the acid solution, ammonia water was added
dropwise with stirring and the amine crystallized out. It was purified by
dissolving in 1N HCl and addition of ammonia, then by 2 crystallizations from
benzene followed by 2 crystallizations from isopropanol, to yield 3-ethyl-
4,5,6,7-tetrahydro-2-methyl-4-oxoindole, melting point 180°C to 181°C.
