Compounds Derived from Chloroacetic Acids

2-Tribromo-l-[4-hydroxy-2-methyl-S-(l-methylethyl)phenyl]ethanone 

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Monhaloacetic acids are compounds derived from acetic acid with the substitution of a halogen to replace one of the hydrogens. Chloroacetate, fluoroac-etate, iodoacetate, and bromoacetate are compounds that vary in toxicity and mode of action although they are closely related. Sodium fluoroacetate was a widely used mammalian pesticide known as compound 1080. Chloroacetic acid is used as a feedstock and is manufactured in large quantities. 

In 1880, Liebermann and Voltzkow (40), and then Voltzkow (41), condensing chloroacetic acid with both ethyl N-phenylthiocarbamate and p-tolylisothiocyanate obtained homologous compounds to which they attributed formulas 40 and 41, whereas their structure probably derives from that of 38 by substituting an aryl group on the cyclic nitrogen. 

Another approach uses reactive alkyl halogen compounds containing a terminal carboxylate group on the other end to form spacer arms off the dextran polymer from each available hydroxyl. In this manner, Brunswick et al. (1988) used chloroacetic acid to modify the hydroxyl groups to form the carboxymethyl derivative. The carboxylates then were aminated with ethylene diamine to create an amine-terminal derivative (Inman, 1985). Finally, the amines were modified with iodoacetate to form a sulfhydryl-reactive polymer (Figure 25.14). 

Hydrogen telluride, generated in situ from aluminum telluride in aqueous tetrahydrofuran containing sulfuric acid, reacted with aliphatic aldehydes to produce dialkyl ditellurium compounds in yields of aproximately 50%. Strong acids are required to obtain acceptable yields of ditellurium compounds. Weak acids (acetic acid, chloroacetic acid) reduce the yields to approximately 10%. In a basic medium (triethylamine), no ditellurium derivative was formed the major product was the alcohol. 

Reactions of Benzolb]thiophens. Reaction of (318), prepared from p-thiocresol and oxalyl chloride, gave (319) with chloroacetic acid and sodium hydride. (319) was converted to many other benzolb]-thiophen derivatives, including (320), which was obtained via side-chain bromination and Friedel-Crafts alkylation. Desulphurization of (320) gave (321),223 compounds (322) were obtained from the reaction... 

Another way to get citronellol is by the reductive dimerization of isoprene with formic acid and triethylamine using a 1% pcdladium phosphine catalyst [32]. The two head-to-tail dimers are formed in up to 79% yields, which can easily be separated from the head-to-head and tail-to-tail dimers by conversion with aqueous hydrochloric acid, yielding 7-chloro-3,7-dimethyl-l-octene. Hydroboration and pyrolysis of this chloro derivative produces a 1 3-mixture of a- and jS-citronellol. The mono-chloro compound can also be oxidized with tert- mty peracetate and a cuprous bromide catalyst to the chloroacetate, which is reduced with LiAJH4 and pyrolyzed to linalool in 64% overall yield. 

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