Ethyl formate, transesterification with

Lactam 299 was prepared from tryptamine and cyano diester 298 by reductive alkylation in about 12% yield. Phosphorus oxychloride cyclization of 299, followed by catalytic reduction, resulted in the corresponding trans disubstituted indolo[2,3-a]quinolizine 300. After transesterification, formylation and methyla-tion were carried out in two subsequent steps with ethyl formate in the presence of triphenylmethylsodium and with an excess of diazomethane to supply ( )-dihydrocorynantheine (163). 

As with inorganic solid catalysts, the most extensively studied system was acetic acid—ethanol [428,432,434,444—448]. Other alcohols used in kinetic studies were methanol [430,449,450], 2-propanol [438], 1-bu-tanol [429,431,433,451—458], allyl alcohol [459], 1-pentanol [434] and ethyleneglycol [460] besides acetic acid, the reactions of formic [450], propionic [443,461], salicylic [430,449], benzoic [453—457] and oleic acids [430,451—453] and of phthalic anhydride [462] have been reported. Investigation of a greater variety of reactants is reported in only one paper [463] six alcohols (C4, Cs and C8) and five acids (mainly dicarboxylic were studied. Transesterification kinetic studies were performed with ethyl formate [437,439,441], isobutyrate [437,439—441] acetate [402, 435—437,439—442], methoxyacetate [441] and acrylate [403,404,464, 465] the alcohols used were methanol [402,435,437,439—442,450],... 

Peptide synthesis. Vinyl esters of amino acids, prepared by transesterification with vinyl acetate, have been used as activated esters in peptide synthesis. The coupling reaction is best carried out in ethyl cyanoacetate, for this solvent suppresses the formation of colored products derived from liberated acetaldehyde. Racemization appears to be slight. 

Pyrrole-based anthranilic acid derivatives have been prepared utilizing a four step sequence starting from arylacetonitriles 4 <04T2267>. Condensation of the latter with ethyl formate followed by treatment with diethylaminomalonate hydrochloride (DEAM-HCl) led to enamine 6. Cyclization and transesterification then gave 3-aminopyrrole-2-carboxylate 7. The acid-mediated cyclocondensation of methylaminoacetaldehyde dimethyl acetal with malonitrile provided a novel synthesis of 2-amino-3-cyanopyrroles, useful building blocks for the preparation ofpyrrolo[2,3- f]pyrimidines <04OL2857>. 

There is an additional factor contributing to the toxicity of cocaine, namely its interaction with ethanol [122] [123], Many cocaine (ab)users simultaneously ingest ethanol, probably to experience potentiation of effects and attenuation of headaches. It is now known that ethanol interferes in two ways with the metabolism of cocaine, first by inhibiting its hydrolysis and second by allowing transesterification to form benzoylecgonine ethyl ester (7.61, Fig. 7.8) commonly known as cocaethylene. These metabolic effects are illustrated by studies in the rat (Table 7.3), with ethanol inhibiting the formation of... 

Oxotitanium acetylacetonate, TiO(acac)2, was found to be a very efficient catalyst for the transesterification of methyl (and ethyl) esters. The mechanism probably involves initial formation from reactant, ROH, of TiO(OR)2(acac)2, which upon complexation with the methyl ester, R CC Me, progresses from (13) to a tetrahedral intermediate containing a TiO bond (14), which rearranges to yield the product, R C02R, and TiO(OR)OMe)(acac)2 (Scheme 4).7... 

In addition to the hydrolysis of cocaine, the purified human liver cocaine methyl ester hydrolase also catalyzed the ethyl transesterification of cocaine with ethanol to form cocaethylene and methanol as shown in figure 1 (Dean et al. 1991 Brzezinski et al. 1994). Both the hydrolytic and the ethyl transesterification reactions increased as the two activities were analyzed in protein fractions obtained during the enzyme purifi-cation by column chromatography. This suggests that the separate activities are catalyzed by the same enzyme. The Km values for cocaine and ethanol of the purified enzyme at pH 7.3 were 116 M and 43 mM, respectively. The carboxylesterase also catalyzes the formation of ethyloleate from oleic acid and ethanol (Tsujita and Okuda 1992 Brzezinski et al. 1994). Other hydrolases or ester transferases have been reported to catalyze similar substrate "ethylation" reactions. 

Transesterification of 2-O-dodecyl a-D-fructofuranoside (21) with ethyl decanoate and SP 435 lipase gave initially the 6-mono-ester 22 which was slowly converted into di-esters, mainly the 1,6-di-ester 23. Addition of zeolite CaA allowed selective formation of either 22 or 23, depending on the reaction time. 

The transesterification of N-(j3-hydroxyethyl)ethylenediamine by p-nitro-phenyl picolinate has been shown to be subject to zinc ion catalysis by Sigman and Jorgensen 27). Their investigations indicate that reaction very probably occurs through the formation of a ternary complex in which zinc ion functions both to lower the pKa of the hydroxyethyl moiety, and to serve as a template for the reaction. The high specificity manifest in this catalytic process is emphasized by the fact that no catalysis of acyl-group transfer occurs when N-((8-hydroxy-ethyl) ethylenediamine is replaced by ethylenediamine, 1,5-diaminopentane, di-ethylenetriamineor aminoethanol. Furthermore, the reactions of the p-nitrophenyl esters of isonicotinic and acetic acids with N-((8-hydroxyethyl) ethylenediamine are not subject to zinc ion catalysis. 

A few drops of triethylamine added to trimethylolpropane and triethyl phosphite, heated with stirring to 100°, then the temp, raised to 130° during 8 hrs. with distillation of the resulting alcohol l-ethyl-4-phospha-3,5,8-trioxabi-cyclo[2.2.2] octane (Y 90%) mixed with benzyl chloride, stirred and heated 12 hrs. at 170° cfs-2-chloromethyl-2-ethyl-l,3-propanediol henzylphosphonate (Y 91%).—The slow removal of alcohol at the lowest possible temp, is essential if by-product formation is to be kept at a minimum during transesterification. F. e. and reactions s. W. S. Wadsworth, Jr., and W. D. Emmons, Am. Soc. 84, 610 (1962). 

The transesterification of ethyl acetate with methanol catalysed by 1,5-diazo-bicyclo[4.3.0]non-5-ene (DBN) (1) is well known, but now it is reported that its activity is considerably enhanced when propylene oxide is present. No mechanism was offered by the authors. The acceleration that was observed is most likely due to the formation of a zwitterionic adduct (2) from propylene oxide and DBN, which would be able as a general base to remove a proton from methanol much more effectively than DBN. 

PolyCethylene terephthalate) is produced by polycondensation of bis(hydroxy-ethyl)terephthalate (BHET) or its oligomers. BHET may be synthesized both by the reaction of dimethyl terephthalte (DMT) and ethylene glycol (EG) and by the direct esterification of EG with terephthalic acid. Although direct esterification has recently gained importance, the DMT method remains the main process for obtaining BHET. This latter process provides the formation of DMT solution in EG, the transesterification of DMT with EG and distillation of methanol with formation of BHET, and finally, BHET polycondensation. The DMT EG molar ratio is 1 2 with an excess of EG (0.2 to 0.5 mol). Preheating of EG to 120 to 160°C and introduction of DMT in the molten state shortens the DMT dissolving time. 

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