2-methyl-3'-hydroxy-1, 1'-diphenylamine was synthesized from the mixture consisting of 3-aminophenol, 3-nitrophenol, and 2-methyl cyclohexanone via vapor phase reaction on 5% Pd/C catalyst. Reaction was allowed to proceed at 203℃ for 5 to 10 hrs in an autoclave-type high pressure reactor. The optimal composition of the reaction mixture was 1 : 2 : 48 in the molar ratio of 3-aminophenol : 3-nitrophenol : 2-methyl cyclohexanone, and the highest yield of diphenylamine derivative was ca. 90% after 6 hrs of reaction timer based on the moles of aminophenol plus nitrophenol introduced. The rate-determining step of overall reaction was hydrogen-abstraction of the intermediate. N-cyclohexylideneaniline species, which was readily formed via condensation of aminophenol and excess cyclohexanone derivative. The hydrogen abstracted was transferred to nitrophenol, which was easily converted to aminophenol via reduction. this replenishing the aromatic amino reactant for formation of tile intermediate. The mechanism of overall reaction was in essence identical to that previously observed in formation of 2-methyl-4-methoxy diphenylamine. a raw-material of fluoran bleat-sensitive dye