Abstract: The invention relates to a process for the synthesis of dibenzofuran by the dehydrocyclization of 2-cyclo-hexenyl-cyclohexanone at high temperature in the presence of air and a catalyst system selected among the known dehydrogenation catalysts.By the claimed process very high yields of dibenzofuran are achieved.

Abstract: A process for the preparation of substituted indolenines of the formula: ##STR1## wherein R is hydrogen, alkyl, aryl or cycloalkyl, halogen, or a functional group selected from among cyano, hydroxyl, alkoxy, nitro or sulphonic groups, and wherein R.sub.1, R.sub.2 and R.sub.3 are the same, or different, and are selected from alkyl, aryl or cycloalkyl radicals, comprising reacting in the presence of an organic solvent an aromatic amine of the formula: ##STR2## with a tertiary hydroxyketone of the formula: ##STR3## wherein R, R.sub.1, R.sub.2 and R.sub.3 have the same meanings as defined above, in the presence of a catalyst selected from mineral acids, organic acids, Lewis acids or ionic exchange resins in acid form, and wherein said aromatic amine is slightly in excess, to form first an imine of the formula: ##STR4## under reaction conditions wherein the solvent is removed by azeotropic distillation, and thereafter continuing the reaction to remove water and cyclizing to the desired indolenines.

Abstract: Diphenylamine, or the alkyl, phenyl, amino, alkoxy, hydroxy or halogen derivative thereof, is prepared through a continuous process wherein a stream of the corresponding imine (e.g. N-cyclohexylidene aniline) in the vapor phase and oxygen are fed to a reactor maintained at a temperature in the range from 300.degree. to 450.degree. C, at a rate providing a contact time between the reactants in the range of 0.1 to 20 seconds.