Methanolysis carboxylic esters

Scheme 5 A proposed concerted mechanism for methoxide promoted methanolysis of carboxylate esters with displacement of aryloxy leaving groups.

A procedure for obtaining indole-3-carboxylate ester from the f-pyrrolidino-o-nitrostyrene intermediates in the Leimgruber-Batcho indole synthesis was demonstrated. Although ethyl chloroformate is evidently not reactive enough, phosgene followed by methanolysis effects f) -carbomethoxylation. Reductive cyclization then gives the indole esters. <95SC95>... 

Ring opening of a bi- or tricyclic /3-lactam, which does not have a bridgehead nitrogen atom and whose relative stereochemistry is known, gives /3-amino acid derivatives where the relative stereochemistry is also known. This idea has been used extensively. For instance, methanolysis of the tricyclic /3-lactams 117 gave a series of 3-amino 4-substituted chromane-2-carboxylic esters 118 (Equation 12) whose relative stereochemistry is known <1999T5567>. 

Zn2 closely parallels that observed in the basic ethanolysis catalyzed by dinuclear complexes 14-Ba2 and 15-Ba2 (Table 8.1). The results obtained in the basic methanolysis of esters catalyzed by the zinc(II) complexes of calix[4]arenes 28-31 decorated with 1,5,9-triazacyclododecane ([12]aneN3) ligands fully confirm the superiority of 1,2-vicinal bimetallic catalysts over their distal regioisomers. Thus, the order of catalytic efficiency 1,2-vicinal 1,3-distal appears to be a substrate-independent feature of upper rim calix[4]arene-based bimetallic catalysts for the cleavage of carboxylate-functional-ized esters, which is unaffected by the nature of the metal ion and of the corresponding ligating unit. 

Fig. 26.1 Bimetallic (a), and trimetallic (b) catalytic mechanism for the basic methanolysis of esters functionalized with a distal carboxylate anchoring group...

DFT Computational Study of the Methanolysis of Carboxylate Esters Promoted by Zn"-Complexed Methoxide (18)... 

Neverov AA, Sunderland NE, Brown RS. Metal ion promoted transesterifications of carboxylate esters. A stmcture/activity study of the efficacy of Zn and La to catalyze the methanolysis of some aryl and aliphatic esters. Org Biomol Chem. 2005 3 65-72. 

Alkyl esters are efficiently dealkylated to trimethylsilyl esters with high concentrations of iodotrimethylsilane either in chloroform or sulfolane solutions at 25-80° or without solvent at 100-110°.Hydrolysis of the trimethylsilyl esters serves to release the carboxylic acid. Amines may be recovered from O-methyl, O-ethyl, and O-benzyl carbamates after reaction with iodotrimethylsilane in chloroform or sulfolane at 50—60° and subsequent methanolysis. The conversion of dimethyl, diethyl, and ethylene acetals and ketals to the parent aldehydes and ketones under aprotic conditions has been accomplished with this reagent. The reactions of alcohols (or the corresponding trimethylsilyl ethers) and aldehydes with iodotrimethylsilane give alkyl iodides and a-iodosilyl ethers,respectively. lodomethyl methyl ether is obtained from cleavage of dimethoxymethane with iodotrimethylsilane. 

The initial study of the La3 +-catalyzed methanolysis of carboxylate esters163 reported the apparent second-order rate constant for La2 + ( OCH3)2-catalyzed methanolysis of some representative examples of aryl esters (2, 5 and 2,4-dinitrophenyl acetate (14)), phenyl benzoate (15) and three aliphatic esters, ethyl acetate, isopropyl acetate (16) and tert-butyl acetate (17). Given in Table 6 are the rate constants for the La3+ and methoxide-catalyzed methanolysis of these esters along with... 

A methyl ester was formed by methanolysis of a trihalide (Equation 32) <2007S225>. Decarboxylation of the /3-ketoacid resulting from hydrolysis has also been reported (Equation 33) <1980LA1917>. A carboxylic acid substituent was reduced to aldehyde with LAH (Equation 34) <1974J(P1)2092>. Thiazine nitrogen probably participates in this reaction. 

Microwave irradiation of a mixture of an acid anhydride, an amine adsorbed on silica gel, and TaCl5/Si02 is a solvent-free method for the synthesis of A-alkyl and A-aryl-imides [47]. Ni(II) promotes the conversion of an acrylamide to ethyl acrylate via a Diels-Alder adduct with (2-pyridyl)anthracene [48], Aromatic carboxylic acids [49] and mandelic acid [50] are efficiently esterified with Fc2(S04)3 XH2O as catalyst. Co(II) perchlorate in MeOH catalyzes the methanolysis of acetyl imidazole and acetyl pyrazole [51]. Hiyama et al. used FeCb as a catalyst for the acylation of a silylated cyanohydrin. The resulting ester was then cyclized to 4-amino-2(5H)-furanones (Sch. 5) [52]. 

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