Chloroformic esterification with

Pyrrole-2-carboxylic acid esters have been prepared from ethyl chloroformate and pyrrolylmagnesium bromide1 2 or pyrrolyllithium,3 by hydrolysis and decarboxylation of dimethyl pyrrole-1,2-dicarboxylate followed by re-esterification of the 2-acid4 and by oxidation of pyrrole-2-carboxaldehyde followed by esterification with diazomethane.4... 

Af -2,2-Bis(ethoxycarbonyl)vinyl-protected amino acids are prepared by reaction of commercially available diethyl 2-(ethoxymethylene)malonate (127) with the respective amino acid in methanolic KOH. This rapid reaction is complete within 5 minutes and leads to the potassium salts. Subsequent acidification with 1M HCl yields the amino acid derivative in 75-90% yield.f This intermediate enamine-type N-protection is of particular interest in chemistry to be performed on the carboxy groups of the amino acids such as esterification with alkyl bromides in the presence of a base. Since cleavage of the enamine entity is achieved by treatment with bromine in chloroform at room temperature, it cannot be used for amino acids sensitive to halogenation such as tyrosine, tryptophan, and methionine (Scheme 61). Based on the experience gained with the enamine-type protection the Al-2-(4,4-dimethyl-2,6-dioxocyclohexylidene)ethyl (Dde) and N-2-(4,4-dimethyl-2,6-dioxocyclohex-ylidene)isovaleryl derivatives were developed as specific side-chain protecting groups (see Section 2.1.2.2.5.2). 

Esterification with mixed acids is often suitable for the preparation of carbohydrate nitrates, but sometimes a less vigorous method is required. For this purpose, a solution of anhydrous nitric acid in chloroform was introduced by Koenigs and Knorr and found suitable for preparing... 

Addition of chloroform to benzaldehyde followed by esterification with acetic anhydride gives the trichloro derivative known as rose crystals or, more commonly by the misnomer, rose acetone. Such misnomers are not uncommon with older fragrance materials. Some... 

Thus, chalcone (26), available via aldol condensation between the appropriate benzaldehyde and acetophenone, was transformed into the 1,3-diarylpropene (27) via a two-step sequence involving ethyl chloroformate and NaBH4, followed by protection of the phenolic hydroxy group as the TBDMS ether. Asymmetric dihydroxylation of olefin (2 7) with AD-mix-a gave an intermediate diol, which was converted into ortho-ester (28) with triethyl orthoformate in the presence of catalytic pyridinium -toluenesulfonate (PPTS), followed by deprotection of the TBDMS ether with TBAF in THE. Treatment of ortho-ester (28) with triethyl orthoformate and PPTS gave an intermediate (27( ,35)- w j -flavan-3-ol formate ester. De-esterification with K2CO3 in THF/methanol and oxidation of the... 

Process aspects Tor extraction ofaceiic acid with amines arc discussed by Rickard al.11 Alcohol diluents gave the highest values of Kd. but the alcohols were subject to esterification with acetic acid upon regeneration by distillation. Ketones appeared to be satisfactory diluents from the standpoint of high KD. Chloroform is a superior diluent because il is a Lewis acid and can interact with the complex.4 However, chloroform is toxic, and this fact may limit its use. 

The most frequently used approaches for derivatizing carboxylic acids are esterification with a variety of single-enantiomer alcohols, or formation of amides with single-enantiomer amines [234,252]. The formation of amide derivatives requires activation of the carboxylic acid by formation of the acid chloride with thionyl chloride, mixed anhydrides with chloroformates, N-acylimidazoles with 1,1 -carbonyldiimidazole or N-acylureas with dicyclohexylcarbodiimide. Esterification reactions generally re-... 

Alkoxycarbonylation followed by esterification provides an attractive alternative derivatization method for amino acid quantitation (Yamamoto et al., 1982 Makita et al., 1982). N-Alkoxycarbonyl methyl esters are prepared by a two-step procedure involving the use of an alkyl chloroformate in aqueous medium, followed by esterification with diazomethane. (Fig. 5) Alk-oxycarbonylahon is performed at room temperature for 10 min, whereas esterification is complete in 3 min at room temperature. 

Triethylamine Esterification with chloroformic acid esters... 

The silica gel may adsorb the esters of the short-chain fatty acids. For the esterification of those acids, a chloroform solution of the Cj—C aliphatic acids (50/rl) is treated with an equal volume of a freshly prepared 1% solution of 2,2,2-trichloroethanol in chloroform, together with 150 /A of heptafluorobutyric anhydride (HFBA) in a closed tube at room temperature for 30 minutes. Excess trichloroethanol is removed by reaction with 50 1 of a 25% solution of palmitic acid in chloroform, added subsequently and left to react at room temperature for 15 minutes. (The trichloroethyl palmitate p>eak comes off the GC column long after the shorter-chain fatty acid ester peaks). Further purification is achieved by shaking with 100 /il of chloroform and 100 1 of 0.1 M HCl the aqueous layer is discarded, and the organic layer is washed with 100 fi of 0.1 M NaOH and evaporated to dryness. The residue is dissolved in 100 fil of diethyl ether for analysis by GC with electron capture detection [46]. 

Copolymers with amorphous A block and liquid crystalline B block have been synthesized. The hydroboration of polybutadiene or butadiene styrene block copolymer with 9-BBN yields the intermediate, which on oxidation, followed by esterification with cholesteryl chloroformate, leads to the formation [4] of the said polymer. 

Polyols were converted into chloroform-soluble trifluoroacetates via esterification with TFAA. Figure 5.4 shows a high-resolution GPC curve of the trifluoroacetates obtained from the ozonolysis products of polybutadiene. 

Preparative Methods prepared by the reaction of [E)-2-(trimethylsilyl)vinyllithium with methyl chloroformate or by carbonation of the corresponding Grignard reagent prepared from (l-bromovinyl)trimethylsilane, giving 2-trimethyl-silylacrylic acid. The methyl ester is prepared from the acid by direct esterification with absolute methanol in the presence of mineral acid, by reaction with diazomethane at low temperature, or by treatment with BF3-MeOH complex. For preparation of various trialkylsilylacrylic acid esters and f-butyl 2-trimethylsilylcrotonate, see the cited references. 

Esterification with acid anhydrides is very widespread, especially for preparative use. Acetyl derivatives are prepared by reacting alcohols with acetic anhydride for identification purposes this method is mainly used with polyhydric alcohols (see p. 311) and with higher-molecular alcohols (sterols, etc.). The alcohol is heated in acetic anhydride, usually in the presence of anhydrous sodium acetate, or also in pyridine, chloroform, or benzene solutions. The isolation is carried out either by diluting the reaction... 

An electrophilic addition of chloroform to SWNTs was followed by hydrolysis and it resulted in the addition of hydroxyl groups to the surface of the nanotubes. Its esterification with propionyl chloride led to the corresponding ester derivatives (Tagmatarchis et al., 2002). 

From Boron Halides. Using boron haUdes is not economically desirable because boron haUdes are made from boric acid. However, this method does provide a convenient laboratory synthesis of boric acid esters. The esterification of boron haUdes with alcohol is analogous to the classical conversion of carboxyUc acid haUdes to carboxyUc esters. Simple mixing of the reactants at room temperature or below ia a solvent such as methylene chloride, chloroform, pentane, etc, yields hydrogen haUde and the borate ia high yield. 

Another appHcation of 4-chlorophenol is in the synthesis of a dmg, ethyl a, a-dimethyl-4-chlorophenoxy acetate [637-07-0] (60), used as a cholesterol-reducing agent. This synthesis involves reaction with acetone and chloroform, followed by ethanol esterification. 

In the literature a number of different techniques for the preparation of a-sulfo fatty acid esters can be found. There is equipment for small-scale and commercial scale sulfonation. Stirton et al. added liquid sulfur trioxide dropwise to the fatty acids dispersed or dissolved in chloroform, carbon tetrachloride, or tetrachoroethylene [44]. The molar ratio of S03/fatty acid was 1.5-1.7 and the reaction temperature was increased to 65 °C in the Final stage of sulfonation. The yield was 75-85% of the dark colored a-sulfonated acid. The esterification of the acid was carried out with either the a-sulfonic acid alone, in which case the free sulfonic acid served as its own catalyst, or with the monosodium salt and a mineral catalyst. 

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