Synthesis 



been very favourably reported by Avery et al. (1937), and by 

 Zimmerman and Hitchcock (1937), whose paper on "Com- 

 parative effectiveness of acids, salts, and esters as growth 

 substances, and methods of evaluating them" provides an 

 interesting discussion. 



^//o-cinnamic acid: see p. 84. Glycerides: see p. 81. 



Naphthalene Compounds (See also p. 119). 



Zimmerman and Wilcoxon (1935) prepared a- and P- 

 naphthalene-acetic acids from the corresponding methyl- 

 naphthalenes by bromination, conversion to the nitrile, and 

 hydrolysis of the nitrile by the procedure of Mayer and 

 Oppenheimer (1916). It may be noted that a-naphthalene- 

 acetic and Y-indolyl-3-butyric acids are the most powerful 

 root-forming acids known (Zimmerman, 1936). For the 

 synthesis of indolyl-butyric acid, see Jackson and Manske 

 (1930). Use of a pure a-naphthyl-acetic acid free from the 

 P-form and from naphthoic acid present in earlier prepara- 

 tions, was reported by Zimmerman and Hitchcock (1937). 

 This was presumably the same as the acid prepared by Wil- 

 coxon (1937) by a procedure based on Rousset's (1897) 

 method. Employing the Friedel and Crafts reaction between 

 naphthalene and ethyl chloroglyoxylate, Rousset obtained 

 a-and p-ketonic esters in yield 50 per cent, of theory ; reduction 

 of the ketone acid then yielded the corresponding glycollic 

 or acetic acid. 



Wilcoxon's paper reviews probably all the existing methods 

 for the preparation of naphthyl-acetic acids. It is of interest to 

 note that Wilcoxon was unable to obtain any naphthyl acid 

 by following the patented procedure of Wolfram et al. (1934)- 



His modification of Rousset's method gave a product 

 (yield 47 per cent, of theory) consisting entirely of the desired 

 a-form of ethyl naphthalene-glyoxylate. 



Reduction of this with sodium amalgam gave a 40 per cent., 

 and with hydrogen and nickel catalyst a 88 per cent., yield of 

 a-naphthalene-glycollic acid. Reduction of the glyoxylate 

 ester with hydriodic acid and red phosphorus gave a 9a per 

 cent, yield of a-naphthalene-acetic acid. 



Ill 



