Carboxylic acids esters, hydrolysis, partial

Partial hydrolysis of carboxylic acid esters GOOR GOOH... 

Partial hydrolysis of carboxylic acid esters s. 7, 13 at low temp. s. A. Adams and R. Slack, Soc. 1959, 3061 Malonic acid monoesters s. 14, 12... 

The most convenient laboratory method for the preparation of 2,4-dimethyl-5-carbethoxypyrrole is that given above. A cheaper method of obtaining large quantities consists in the partial hydrolysis of 2,4-dimethyl-3,5-dicarbethoxypyrrole with sulfuric acid, followed by decarboxylation. The ester has been obtained also by the alcoholysis of 5-trichloroaceto-2,4-dimethyl-pyrrole in the presence of sodium ethylate. The free acid has been obtained fronii-[2,4-dimethylpyrrole-5]-2,4-dimethylpyrrole-5-carboxylic acid and from 2,4-dimethylpyrrole-5-aldehyde. ... 

A synthetically useful virtue of enol triflates is that they are amenable to palladium-catalyzed carbon-carbon bond-forming reactions under mild conditions. When a solution of enol triflate 21 and tetrakis(triphenylphosphine)palladium(o) in benzene is treated with a mixture of terminal alkyne 17, n-propylamine, and cuprous iodide,17 intermediate 22 is formed in 76-84% yield. Although a partial hydrogenation of the alkyne in 22 could conceivably secure the formation of the cis C1-C2 olefin, a chemoselective hydrobora-tion/protonation sequence was found to be a much more reliable and suitable alternative. Thus, sequential hydroboration of the alkyne 22 with dicyclohexylborane, protonolysis, oxidative workup, and hydrolysis of the oxabicyclo[2.2.2]octyl ester protecting group gives dienic carboxylic acid 15 in a yield of 86% from 22. 

The reagent most commonly used for oxidation of ethers is RuO. The subject is well summarized in an early review by Gore [75], Primary methyl ethers RCHjOCHj are oxidised to esters RCOOCH, and secondary methyl ethers R R CjHjOCHj to ketones R COR while with benzyl ethers PhCH OR the esters PhCOOR are formed. For cyclic ethers, the carbon atoms adjacent to the O atom are oxidised, and if there are two secondary carbon atoms the main products are lactones, sometimes with partial hydrolysis to carboxylic acids [75], There is a short review on oxidation of ethers by RuO, principally on the mechanisms involved [76],... 

Enzymes such as pig liver esterase have been successfully applied in enantioselective hydrolysis of allenyl esters on a scale of 2 mmoles131. This provides the enantiomerically enriched allene-carboxylic acid as well as the ester of opposite configuration, by what is in fact a catalytic kinetic resolution (6-90% oy). Conversely, partial enantioselective esterification of /1-hydroxy-allenes (3-72% oy) employing lipases has been reported132,133. 

Condensation of y-picoline with mesoxalic ester yielded 4-(j8,j8-diethoxycarbonylvinyl)pyridine (35). The unsaturated ester (35) was hydrogenated with platinum catalyst to form 36 which was treated with bromine. 4-(j8-Bromo-j8,j8-diethoxycarbonylethyl)-piperidine (37) was obtained and was cyclized with pyridine to 2,2-die th 0 xycarbony 1 quinuclidine (38). Hydrolysis of 38 and partial decarboxylation gave quinuclidine-2-carboxylic acid (39). 

A new metabolite from Streptomyces olivaceus has been shown to be (2S)-1-oxo-2,3-dihydropyrrolizine-3-carboxylic acid (15b) by total synthesis. The pyrrolizine ring was formed from the pyrrole (14) by stereoselective cyclization with phosphorus pentoxide in toluene in 37% yield. Partial racemization occurred during the hydrolysis of ester 15a.21... 

For example, EC yields polymers containing blocks of poly-ethers and polycarbonates. due to the partial elimination of C02 [246], while its hydrolysis produces high-purity 1,2-diols. Furthermore, CCs react readily with carboxylic acids to form 2-hydroxyethyl esters [177, 247, 248]. 

In some cases, the requisite cinnamic acid was commercially available and could be reduced after esterification. Partial reduction was seen when the carboxylic acid was used as the substrate. After hydrolysis and silylation, the desired intermediate ester was obtained. 

A new type of copolymer resist named ESCAP (environmentally stable chemical amplification photoresist) has recently been reported from IBM [163], which is based on a random copolymer of 4-hydroxystyrene with tert-butyl acrylate (TBA) (Fig. 37), which is converted to a copolymer of the hydroxystyrene with acrylic acid through photochemically-induced acid-catalyzed deprotection. The copolymer can be readily synthesized by direct radical copolymerization of 4-hydroxystyrene with tert-butyl acrylate or alternatively by radical copolymerization of 4-acetoxystyrene with the acrylate followed by selective hydrolysis of the acetate group with ammonium hydroxide. The copolymerization behavior as a function of conversion has been simulated for the both systems based on experimentally determined monomer reactivity ratios (Table 1) [164]. In comparison with the above-mentioned partially protected PHOST systems, this copolymer does not undergo thermal deprotection up to 180 °C. Furthermore, as mentioned earlier, the conversion of the terf-butyl ester to carboxylic acid provides an extremely fast dissolution rate in the exposed regions and a large... 

The partial hydrolysis of 4a with methanolic potassium hydroxide followed by selective carboxylic acid reduction with excess borane and treatment of the resulting monoalcohol with methanesulfonyl chloride affords methyl 4-0-methanesulfonyl-2,3-0-isopropylidene-L-threonate (43). Facile displacement of the mesylate with azide followed by ester hydrolysis and catalytic reduction to an amine provides 4-amino-4-deoxy-2,3-0-isopropylidene-L-threonic acid (44). Mild acidic deprotection and ion-exchange desalting of 44 yields (2i ,3 S)-4-amino-4-deoxy-L-threonic acid (45), which has been utilized for the preparation of anthopleurine 46, the alarm pheromone of the sea anemone Anthopleura elegantissima [4] (Scheme 11). 

The most prominent cellulose ester produced on the industrial scale is cellulose acetate. The reaction is usually performed with acetic anhydride and with sulfuric acid as a catalyst. To minimize heterogeneities, acetylation is allowed to run nearly to completion, and subsequently partial ester hydrolysis is initiated by the addition of water until a desirable solubility is achieved that corresponds to a DS of about 2.5. Such higher acyl homologues as propanoyl or butanoyl exhibit more thermoplastic properties. Many specialized esters such as chiral (-)-menthyloxyacetates, furan-2-carboxylates, or crown-ether-containing acylates have been prepared on the laboratory scale and characterized by NMR spectroscopy. Various procedures have been applied, using anhydrides and acyl chlorides as acylating agents in combination with such bases as pyridine, 4-dimethylaminopyridine (DMAP), or iV,iV -carbonyldi-imidazole. The substitution pattern of cellulose acetates has also been modified by postchemical enzymatic deacetylation. Cellulose 6-tosylates have been used as activated intermediates for nucleophihc substitution to afford 6-amino-6-deoxy, 6-deoxy, or 6-deoxy-6-halo-celluloses. ... 

The reaction of 3-cyclohexene-1-carboxylic acid with ECH (molar ratio 1 8) was investigated at 65-85 °C in presence of a catalyst (KCl or tetramethylammo-nium chloride). After 2 h the formation of the chlorohydrin ester was completed with 100% quantitative yield. However, the hydrochlorination results in a low yield of epoxy groups and a low conversion of chlorohydrin to epoxy groups. The alkali partial consumption for hydrolysis of the ester groups, even at room temperature, is another reason. 

For the partial synthesis, a regio- and stereoselective reaction is required, in which a bond with defined stereochemistry is formed exclusively between the carboxylic acid and the carbohydrate at the anomeric carbon atom. Due to the polyene system and the ease of the hydrolysis of the ester bond at the anomeric carbon atom, the application of protecting groups on the carbohydrate is restricted. Therefore a method using unprotected carbohydrates has been developed. Crocetin-di(P-D-glucosyl) ester (543) was synthesized in 70% yield by the reaction of crocetin-diimidazolide (4) or crocetin-di(l,2,4-triazolide) (5) and unprotected p-D-glucose in pyridine in the presence of a base [5]. The esterification takes place exclusively at the anomeric carbon atom and produces only the p-anomer [6]. The method was also applied to 8 -apo-P-caroten-8 -oic acid (486) and to other carbohydrates [7]. 

Potassium hydroxide Carboxylic acids from their esters Partial hydrolysis... 

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