Production of Coumarins from Maleic and Malic Acids
Journal of Industrial & Engineering Chemistry
RESEARCH DEPARTMENT, THE BARRETT CO., 40 RECTOR ST., NEW Y O R K , N. Y . The following work was undertaken in order to find out it it were possible to develop a commercial synthesis of coumarin from malic acid,2 and, if such a synthesis proved uneconomical, to determine whether other coumarin derivatives were of value as perfumes or flavors. As a matter of general interest a few condensations were attempted with maleic acid. The malic acid was the synthetic inactive acid made by the hydration
... e by the hydration of maleic acid obtained by the catalytic oxidation of b e n~e n e .~ The m-cresol was of coal-tar origin and was partly separated from the para isomer by the method of F. Elger.4 PROCEDURE The aliphatic acid was added to the phenol and condensing agent contained in a test tube inserted in an oil bath a t the desired temperature. Foaming usually resulted upon stirring, and the solutions became yellow or orange colored. After the evolution of gas had ceased, the contents of the tube were poured over ice and the resulting precipitate filtered off, The precipitate, in the runs where phenol was used, was usually found to be fumaric acid. The filtrate was shaken up with ether and the ether solution examined for coumarin. The absence of the characteristic coumarin odor was considered to be an indication of failure to secure that product. EXPERIMENTAL SERIES I-Equal weights of phenol and maleic acid were heated a t temperatures ranging from 100' to 160°, for times ranging from 40 min. to 5 hrs., with 96 per cent sulfuric acid and with zinc chloride without securing any coumarin. SERIES 11-A number of runs were made with phenol and malic acid in a manner similar to the above without the isolation of any coumarin. Beside the condensation agents of Series I, the following were also tried: 100 per cent sulfuric acid, sodium acetate and zinc chloride, potassium acid sulfate, stannic chlorjde, pyridine in 100 per cent sulfuric acid, phosphorus pentoxide, and aluminium chloride. The manner of adding the ingredients was varied without securing the desired coumarin. SERIES 111-The authors followed the procedure of Fries and Klostermanns which was in general the same as that used in the preceding series, except that the precipitate which formed when the reaction mixture W R S poured on ice was taken up in 50 per cent alcohol and crystallized. This gave a fairly pure 4-methylcoumarin, which became very pure upon one recrystallization from 50 per cent alcohol containing a little boneblack. The yields given in Table I are based upon the recrystallized 4-methylcoumarin of melting point 128' C . The unchanged cresol was regainedby steam distillation of the original filtrate. The malic acid which did not react with the cresol was entirely lost by this process, and no attempt was made to recover any products from it. Experiments showed that with a m-cresol of purity of 84 per cent and a dry malic acid, a yield of approximately 40 per cent of crystallized methylcoumarin could be obtained.