Chlorine Chlorobenzyl chloride

The reaction is a Friedel-Crafts alkylation in which 4-chlorobenzyl chloride serves as the carboca-tion source and chlorobenzene is the aromatic substrate. Alkylation occurs at the positions ortho and para to the chlorine substituent of chlorobenzene. 

By the action of chlorine on benzyl chloride, in presence of iodine as catalyst, />-chlorobenzyl chloride is formed ... 

The chlorination of benzyl chloride over H-K-L, K-L, K-beta, K-mordenite, K-ZSM-5, K-Y, and K-X, and in the absence of catalyst, at 353 K produces a mixture of 2-chlorobenzyl chloride (2-CIBC), 3-chlorobenzyl chloride (3-CIBC),... 

One representative synthesis of prothioconazole starts [95] with the addition of the Grignard derivative of 2-chlorobenzyl chloride on the carbonyl double bond of chloromethyl 1-chloro-cyclopropyl ketone (Scheme 17.19). The untouched chlorine atom of the chloromethyl group is then classically substituted with 1,2,4-triazole. From this intermediate, one way to obtain the 2,4-dihydro-3H-l,2,4-triazole-3-thione of prothioconazole is by direct lithiation of the 1,2,4-triazole at position 5 with n-butyl lithium and reaction with sulfur. The commercially available compound is a mixture of two enantiomers (chirality of the quaternary carbon bearing the hydroxy group). 

For the production of the necessary chrysanthemum acid substituent , 4-chlorotoluene is chlorinated photochemically and the 4-chlorobenzyl chloride converted into the nitrile with sodium cyanide. Base-catalysed introduction of the isopropyl group and subsequent hydrolysis of the nitrile, followed by chlorination, yields 2-isopropyl-(4-chlorophenyl)-acetyl chloride as an intermediate component for the production of fenvalerate. 

Schiff base formation in the Busch reaction may be avoided by employing N-( 1 -chlorobenzyl)benzimidoyl chloride, in which the aldehyde one-carbon fragment is already incorporated into the N-(l-chlorobenzyl) moiety both chlorine atoms participate in the reaction with arylhydrazine, to give modest yields of a A3-l,2,4-triazoline (Scheme 5) (79ZOR1181). 

Reaction schemes 257,258 and 259 gave some examples of some modes of formation of this important class of pyrethroids. The technical processes however, in order to obtain products as pure as possible, consists of the esterification of the acid chloride. Particularly sensible optically active acid chlorides may be obtained by chlorination with the system oxalyl chloride/DMF at lower temperatures [789]. In case of free cyanohydrine an acid scavenger is necessary [789 a], Alternatively, zinc chloride catalyzes the addition of an acid chloride to the aldehyde 280 to give the a-chlorobenzyl esters [790], which easily react with sodium cyanide [791] to give particularly clean products [792]. 

---