4-Chlorobenzyl alcohol

J. Chem., Sect. B, 1986,25, 228.) It appears to be a selective oxidant for benzyUc alcohols, e.g. treatment of 2-chlorobenzyl alcohol with PBC for 3 h in chloroform at reflux gives the corresponding aldehyde in 95% yield. However, it has not been widely adopted. 

M. N. Bhattacharjee, M. K. Chaudhuri, H. S. Dasgupta, N. Roy and D. T. Khathing, Synthesis, 1982, 588. Pyridinium Bromochiomate (PBC) has also been prepared. (N. Narayanan and T. R. Balasubramanian, Indian J. Chem., Sect. B, 1986, 25, 228.) It appears to be a selective oxidant for benzylic alcohols, e.g. treatment of 2-chlorobenzyl alcohol with PBC for 3 h in chloroform at reflux gives the corresponding aldehyde in 95% yield. However, it has not been widely adopted. 

In mammalian species, CS rapidly hydrolyzes to form 2-chlorobenzaldehyde and malononitrile (Leadbeater, 1973 Paradowski, 1979 Rietveld et a/., 1986). The malononitrile intermediate is further metabolized from two cyanide moieties, which are converted to thiocyanate (Cucinell et al, 1971). The aldehyde intermediate undergoes oxidation to 2-chlorobenzoic acid or reduction to 2-chlorobenzyl alcohol. These metabolites are conjugated and excreted in the urine. 

High-boiling alcohols are sometimes better dehydrogenated in the liquid phase in presence of a hydrogen-acceptor such as copper and nitrobenzene or w-dinitrobenzene. The preparation of o-chlorobenzaldehyde in 86% yield from 2-chlorobenzyl alcohol at 205-210° may be cited as example.432... 

Urine and bile samples were assayed for the supposed intermediates of (CI-HPA), i.e. 2-chlorobenzyl alcohol (Cl-BzOH), 2-chloro-benzaldehyde (CI-BzAld), and 2-chlorobenzoic acid (CI-BzA), however, under the conditions used, only trace amounts of (CI-BzA) were detected by GLC. 

Scheme 13 Photo-oxidation of -chlorobenzyl alcohol by Fl-2Sc via photoinduced electton transfer. (From Ref. 114.)...

The reaction of methyl 10, l l -dihydropyrrolo[ l, Z-b [ l, 2,5]bcnzothiadiazcpinc-l l -acetate 5,5-dioxide 73 or the corresponding ethyl ester 74 with potassium hydroxide in EtOH at 25 °C gave the acid 75 (Scheme 14), which upon treatment with trifluoroacetic anhydride in tetrahydrofuran (THF) underwent intramolecular cyclization to afford 76. The 1,2,5-thiadiazepines 73 and 74 were then heated with an excess of concentrated ammonium hydroxide to give the carboxamide 77. The acid 75 upon reaction with 4-chlorophenol, 4-chlorobenzyl alcohol, or 4-chloroaniline in the presence of iV-(3-dimethylaminopropyl)-iV -ethylcarbodiimide hydrochloride (EDCI) and 4-dimethylaminopyridine (DMAP) afforded the respective esters and amide 78-80 <1996FES425>. 

A benzyl group is C6H5CH2—. Benzyl alcohol is therefore C6H5CH2OH and o-chlorobenzyl alcohol is... 

Our initial experiments were performed on p-chlorobenzyl alcohol and employed two equivalents of CuCl Phen. It was rather disappointing to find that, beside NaOAc, all the other bases tested were far less efficient than K2C03 (10). However, during the course of these optimization studies, a dramatic influence of the solvent on the reaction rate was uncovered. For example, a 3-4-fold acceleration was obtained when toluene was substituted for benzene. In contrast, replacing benzene by m- or p-xylene resulted in a decrease in the rate... 

All of these control experiments are consistent with a mechanism in which the stilbenes 5 are in dynamic equilibrium with the equivalent benzylic alcohols 4 and the oxidative-cleavage reaction occurs on the latter. This equilibrium explains 1) the observed requirement for water for the stilbene oxidations 2) the unsymmetrical product distribution from both the alcohols and stilbenes and 3) the enhanced reaction rate of the chlorobenzyl alcohol 4b as compared to the stilbene analogue 5b at 120 °C. 

The substituted benzyl alcohols listed below are prepared in a similar manner from the corresponding aldehydes in the yield indicated vanillyl alcohol, m.p. 113-114°, recrystallized from benzene, 95% anisyl alcohol, b.p. 127-130°/8 mm., 92% piperonyl alcohol, m.p. 52-53°, recrystallized from a mixture of ether and petroleum ether, 91% p-chlorobenzyl alcohol, m.p. 71-72.5°, recrystallized from ben-zene-ligroin mixture, 92% o-chlorobenzyl alcohol, m.p. 64 -65°, 96% p-bromobenzyl alcohol, m.p. 76-76.5°, 96%. 

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