2-Chlorobenzyl esters

Chlorobenzyl esters have been proposed by Prestidge et These esters are readily prepared by the copper-catalyzed hydrolysis method.The 4-chlorobenzyl ester is twice as stable as the benzyl ester toward hydrolysis with TFA/CH2Q2 (1 1) at 45 °C, but is quantitatively cleaved by liquid HF at 0 °C within 30 min. The 4-bromobenzyl esters have also been proposed,f l although only sporadic application is reported [H-Asp(0-4-BrBzl)-OH mp 220-223 °C [o]d +14.1 (c 2, 80% AcOH) Boc-Asp(0-4-BrBzl)-OH mp 128.5-130 °C [o]d -15.5 (c 2.08, DMF)]. 

Protection of carboxyl groups, p-Chlorobenzyl esters are about twice as Stable as benzyl esters to hydrolysis by trifluoroacetic acid in methylene chloride at 45°. They can be removed by liquid HF at 0°. These esters are recommended for protection of the P- and y-carboxyl group of aspartic acid and glutamic acid in the synthesis of moderate-sized peptides. 

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]. 

Nucleophilic substitution of the halogen atom of halogenomethylisoxazoles proceeds readily this reaction does not differ essentially from that of benzyl halides. One should note the successful hydrolysis of 4-chloromethyl- and 4-(chlorobenzyl)-isoxazoles by freshly precipitated lead oxide, a reagent seldom used in organic chemistry. Other halides, ethers, and esters of the isoxazole series have been obtained from 3- and 4-halogenomethylisoxazoles, and 3-chloro-methylisoxazole has been reported in the Arbuzov rearrangement. Panizzi has used dichloromethylisoxazole derivatives to synthesize isoxazole-3- and isoxazole-5-aldehydes/ ... 

With dichloroethane as solvent, approximately fourth-order kinetics were obtained, the order in aromatic being approximately one. The rates of reaction of 4-chlorobenzyl benzenesulphonate with mesitylene and pentamethylbenzene at 50 °C were 0.12 and 1.1 respectively, and for reaction of the 3-nitrobenzyl ester with pentamethylbenzene, 0.009 (at 70 °C) and 0.012 (at 80 °C) these results correspond to the previously observed orders of reactivity. 

C3H5S 870-23-5) see Altizide allyl(l-methyl-2-pentynyl)malonic acid diethyl ester (C16H24O4 101448-52-6) see Methohexital 4-allyloxy-3-chlorobenzaldehyde (CigH Cl02, 58236-91-2) see Alclofenac 4-allyloxy-3-chlorobenzyl chloride (C Hi()Cl20 20788-43-6) see Alclofenac 4-allyloxy-3-chlorobenzyl cyanide (C, H C1N0 20788-44-7) see Alclofenac... 

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>. 

Ml - 1H-INQAZGLE-3-CARBOXYLXC ACID, l-(o-CHLOROBENZYL)-, 2,3-OIHYOROXYPROPYL ESTER... 

N1 1H-INDAZ0LE-3-CARB0XYLIC ACID, l-(p-CHLOROBENZYL)-i 1.3-DIHYDROXY-2-PROPYL ESTER... 

HI - 1H-INOAZOLE-3-CARBOXYLIC ACID l-(p-CHLOROBENZYL)-, 2-HYOROXYETHYL ESTER RN - 50264-99-8... 

Figure 17 Orientation of the side chains of the left- and right-handed a-helices of poly( -chlorobenzyl-L-aspartate). The solid arrows represent the direction of the C—Cl, ester, and amide dipoles, respectively.10...

Fair yields of halomalonic esters are obtained by alkylation of malonic esters with ethylene bromide, " o-chlorobenzyl halides, and 1-bromo-4-chl orobutan e. 

Mitchell has reported that benzyl a-chlorobenzyl sulfides are cleanly converted into stilbenes on successive treatment with PPhs and Bu OK (Scheme 13). Desulfurization of an intermediate thiirane by PPh3 is a likely pathway for this reaction. Benzyl a,a-dichlorobenzyl sulfides are converted into diphe-nylacetylenes under the same conditions." Viehe has reported that pyrolysis of ot-halo-a-alkylthio esters, ketones and nitriles under reduced pressure furnishes a,p-unsaturated esters, ketones and nitriles respectively it is probable that these reactions also take place via intermediate thiiranes. a-Chlorophenacyl phenacyl sulfide is converted into ( )-dibenzoylethylene on treatment with EtsN. ... 

A soln. of 4-amino-4 -chlorodiphenylmethane, methyl acetoacetate, and one drop of 5%-HOI in methylene chloride refluxed until no more water is collected in a water separator —y methyl / -(4-p-chlorobenzyl-anilino)-crotonate. Y 97%.—The methyl esters give better yields than the ethyl esters, both in the above condensation, and in a following ring closure to quinolines (cf. 5, 614). (F. e. s. C. E. Kaslow and R. D. Stayner, Am. Soc. 70, 3350 (1948).) s. a. 4, 750... 

Synonyms Acar Acaraben Acaraben 4E Akar Akar 50 Akar 338 Benzilan Benz-o-chlor Chlorbenzilat Chlorbenzilate Chlorobenzylate Compound 338 4,4 -Dichloroben-zilate 4,4 -Dichlorobenzilic acid ethyl ester ENT 18596 Ethyl 4-chloro-a-(4-chlorophe-nyl) -a-hydroxybenzene acetate Ethyl-4,4-dichlorobenzilate Ethyl-p,/> -dichlorobenzi-late Ethyl-4,4 -dichlorodiphenyl glycollate Ethyl-p,y-dichlorodiphenyl glycollate Ethyl-2-hydroxy-2,2-bis(4-chlorophenyl)acetate Folbex Folbex smoke-strips G 338 G 23,992 Geigy 338 Kop-mite NCI-C00408 NCI-C60413 RCRA waste number U038. 

A reaction sequence as outhned in Reaction scheme 119, but using an a-chlorobenzyl-phosphone ester 224 as Horner-olefination component, gives the add 223 for the tickicide flumethrin [426-430) ... 

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