SYNTHESIS OF 3-HYDROXY-2-NAPHTHOIC ACID ANILIDE CATALYZED BY PHOSPHORUS (III) COMPOUNDS IN VARIOUS MEDIA

Catalysis with phosphorus P(III) compo­unds (phosphorus trichloride and phospho­rous acid) in the acylation of aniline with 3=hydroxy=2=naphthoic acid in various media (toluene, octane, chlorobenzene, para=­xylene, ortho=xylene, ortho=chlorotoluene, mesitylene, pseudocumene, n.=deсan, ortho= di­chlo­ro­benzene, mixtures of ortho=xylene with nitrobenzene) upon boiling and vigorous distillation of water leads to the formation of 3=hydroxy=2=naphthoic acid anilide. With an increase in the reaction temperature in the range from 111 (toluene) to 170 °C (pseudo cumene), a monotonous increase in the initial rate of formation of the target product is observed. In this case, the temperature depen­dence of the logarithm of the velocity obeys the Arrhenius equation, and the activation energy Ea is 66.2 kJ/mol. Higher-boiling n.=decane (175 °С) and ortho=dichlorobenzene (180 °С) fall out of this dependence, in which the initial rate of formation of anilide 3=hydroxy=2=naphthoic acid, compared with that for pseudocumene (170 °С), decreases. The latter may be due to the decomposition or oxidation of the catalyst at such a high temperature with the transition of P(III) to P(V), which does not have catalytic activity. The interaction of aniline with 3=hydro­xyl=2=naphthoic acid proceeds as a series of sequential and parallel reactions in which, in addition to 3=hydroxyl=2= naphthoic acid ani­lide, 3=aniline=2=naphthoic acid and its anilide are formed as impurities. The most acceptable solvents are ortho=xylene and ortho=chlorotoluene with boiling points of 146 and 156°C, in which the yield of the target product is up to 98%. Below 146 °C the reaction proceeds at a relatively low rate; above 156°C the amount of impurities increases significantly, mainly in parallel with an increase in the reaction temperature, and the maximum yield of 3=hydroxyl=2=naphthoic acid anilide decreases. This requires its additional purification, significantly complicating the technological process. The addition of 10–20% by volume of nit­robenzene to ortho=xylene leads to an increase in the yield of 3=oxy=2=naphthoic acid anilide by 1.25–1.42 times in the temperature range of 146–148°C with increasing solvent polarity (ε), respectively, from 2.3 to 7.64. This may be due to an increase in the quantity of the monomers of the catalyst and/or 3=oxy=2=naphthoic acid and aniline in reaction mass and the speed of water separation.