Process for the preparation of spiro[(4-cyclohexanone)-[3]indol]-2'[1'H]-one derivatives

The invention relates to a process for the preparation of spiro[(4-cyclohexanone)-[3H]indol]-2'[1'H]-one derivatives of the general formula I wherein R1 and R2 independently stand for hydrogen, C1-4alkyl, C1-4alkoxy, C1-4alkylthio, C1-4polyfluoroalkyl, C1-4polyfluoroalkoxy, C3-7cycloalkyloxy, C3-7cycloalkylthio, phenoxy, benzyloxy or nitro group-, characterized by reacting an indolin-2-one derivative of the general formula II wherein R1 and R2 are as defined above-with a compound capable for introducing a protective group, selected from 2-tetrahydropyranyl, 1-diethoxy-methylene or C1-4alkoxycarbonylethyl group, coupling the compound of general formula III, thus obtained-wherein R1 and R2 are as defined above and A stands for a protective group, selected from 2-tetrahydropyranyl, 1-diethoxy-methylene or C1-4alkoxycarbonylethyl group-with an acrylic acid C1-4ester, cyclizing the resulting compound of the general formula IV wherein R1, R2 and A are as defined above, R3 stands for C1-4 alkyl group-, eliminating the -COOR3 group and the A protective group of the keto-ester of general formula V wherein R1, R2, R3 and A are as defined above, optionally without isolation of the compounds of the general formulae IV