Search for insecticides – Part IV

A.B. Sen & P. M. Bhargava

Published in: Journal of the Indian Chemical Society, 1949, 26, 366-370

Abstract:

5-Chloro -(I), 3:5-dichloro-(II), 4-methyl-5-chloro-(III) and 5-ωωω-tetrachloro(IV) -2 –hydroxy-aceto phenones have been prepared by Fries reaction. 3-Chloro-2-hydroxyacetophenone (V) and (I) have been obtained by the Friedel-Crafts reaction between acetyl chloride and o- and p-chlorophenols respectively, and subsequent hydrolysis of the acetates formed. Methyl, ethyl and propyl ethers of (I),( II ), ( III ) and (V) have been prepared.

In extension of our previous work on this subject (this Journal, 1948, 25, 277; 1949; 26, 243, 2 7) we have now synthesised a number of halogen-substituted hydroxyacetophenones and their alkyl ethers with a view to studying them for their possible insecticidal action. These compounds are expected to possess good insecticidal action as they contain in their molecule the residues of different inhalation narcotics (viz., CCI3 , COCH3 , COCCl3, OCH3 etc.) attached to the poisonous chlorobenzene ring; that this type of combination is essential for a good contact insecticide is already known (Busvine, Nature, 1935 , 156, 169). Five hydroxyketones, viz., 5-chloro- (I), 3:5-dichloro- (II ), 4-methyl-n-chloro- (III) , 5-ωωω- tetrachloro- (IV) and 3- chloro- (V) 2-hydroxy-acetophenones have been prepared ; (I), (II), (III ) and (V) have been subsequently converted into their methyl, ethyl and propyl ethers. It may be mentioned that a number of alkyl halogen phenols have already been shown to possess good bactericidal properties (Klarmann , Shternov and Gates, J . Amer. Chem., Soc., 1933,55 , 2576).

(I), (II), (III) and(V) have been prepared by the Fries rearrangement of the corresponding acetates. The first three of these compounds have been previously obtained by this method by several authors (Wittig, Ber., 1924, 57, , 1270 ; Annalen , 1926, 446, 155; Karrer et al., Helv. Chim. Acta, 1930, 13, 1308; Klarmann et al., loc. cit. Chien and Yin, J . Chinese Chem., Soc., 1939, 7,40; Rosenmund and Schnurr, Annalen , 1928, 460, 56) . o-Chlorophenyl acetate could not be rearranged even on heating at 140° for 8 hours with 1 mole of anhydrous aluminium chloride.

The Friedel-Crafts reaction between acetyl chloride and p – and O-chlorophenols in presence of anhydrous aluminium chloride resulted in a formation of the acetates of 5-chloro and 3-chloro-2-hydroxy-acetophenones respectively in very good yields (ef. Nencki and Stoeber, Ber., 1897, 30, 1771 ; Claus, Chem. Zentrl. 1898 , II, 158 ; these authors have carried out the above reaction in presence of anhydrous ferric chloride, and obtained 5-chl oro-2- hydroxy- and,3 -chloro- 4 – hydroxy- acetophenones in the case of p- and o- C’hlorophenols respectively. These acetates yielded the corresponding phenols on hydrolysis with alkali.

The methyl, ethyl and propyl ethers of (I), (II), (III) and (V) were obtained in good yields (60-90 %) by using dimethyl sulphate, ethyl iodide and propyl bromide respectively. Methyl ethers of 2- hydroxy-5-chloro- and 2-hydroxy-4-methyl-5-chloro- acetophenones have been previously described, the former having been obtained by the action of acetyl chloride on methyl ether of p-chlorophenol in presence of anhydrous aluminium chloride (Wittig, Ber., 1924, 57, 93) or by methylation of the corresponding hydroxy compound with methyl iodide (Chakravarti and Dutta, J. Indian Chem. Soc ., 1940, 17, 66), and the latter by the methylation of 2-hydroxy-5-chloro-4-rnothylacetophenone by dimethyl suphate (Wittig, Annalen, 1926, 446,155).

All the o-hydroxyacctophenones prepared, gave the Pyman’s test (Gulthard, Marshall ane Pyman, J. Chem. Soc., 1930, 280) for o-hydroxy- ketones and also gave intense violet coloration with 1% ferric chloride. The ethers obtained are insoluble in water, dilute alkali or acids, but dissolve in all common organic solvents.

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Search for insecticides – Part IV. A B SEN & P M BHARGAVA. Journal of the Indian Chemical Society, 1949, 26, 366-370.

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