Methyl diesters

Dimerization of methyl crotonate has been carried out with alkaline earth metal oxides as basic catalysts 15). The reaction proceeds by Michael addition, which is initiated by abstraction of an allylic hydrogen of methyl crotonate by the basic site to form the allylic carbanion, which attacks a second methyl crotonate molecule at the jS-position to form a methyl diester of 3-methyl-2-vinylglutaric acid. The diester undergoes a double bond migration to form the final E- and Z- isomers of 3-ethylidene-3-methylglutaric acid dimethyl ester (MEG) (Scheme 22). 

V -terf-Butyloxycarbonyl-A-fluorenylmethoxycarbonyllanthionine O-Allyl O -Methyl Diester (15) 33 Fmoc-L-Cys-OAl (825 mg, 2.15 mmol) and a catalytic amount of CS2CO3 (ca. 20 mg) were added to a soln of Boc-AAla-OMe (430 mg, 2.14 mmol) in MeCN (10 mL). The mixture was stirred for 2h, then diluted with H20 (lOmL) and extracted with EtOAc (2x20mL). The EtOAc layers were combined, washed with H20 (2 x 20mL), brine (20 mL), dried (MgS04), and the solvent removed under reduced pressure. The residue was purified by column chromatography (silica gel, petroleum ether/EtOAc/AcOH 75 25 1) yield 0.9 g (72%) the diastereomers were separated by HPLC. 

The para-methyl diester of ODA/PMDA had a weight loss of 16.9% at 495°C... 

Only one mole of methanol,is used in this reaction. If two or more moles had been used in the presence of acid the product would have the methyl diester. The reaction would be ... 

New Cooxidants for Dihydroxylation. In recent studies, several oxidants, 02, air, NaC102 (sodium chlorite), NaOCl (sodium hypochlorite), PhSe(0)Bn, Ba(C10)3, and Me3NO 8- were successfully used as cooxidants in Os-catalyzed dihydroxylation of olefins. For instance, Donohoe reported on the use of Me3N0 as a cooxidant in the dihydroxylation process, which allows the synthesis of ( )-l-epiaustraline in 14% overall yield from iV-Boc-p3Trole 2,5-methyl diester (eq 47). The construction of syn-diol moiety is employed by means of 0s04-Ba(C10)3 oxidation (eq 48). ... 

A suitable a-Neu5Ac- 2- 8)-a-Neu5Ac donor is the glycosyl fluoride of the fully acetylated methyl diester carrying phenylthio groups at C-3 of both rings. The synthesis of the Ats-neuraminic acid l,2 8, 9 -lactam 65 has been reported/ ... 

The S5mthesis runs via transesterification, amidation and thiol-ene reactions to get aliphatic diols containing ester, these diols are then reacted with a biobased methyl diester. Most of these polyesters display a good thermal stability with temperature at 5% weight loss in the range 330-350°C. 

The same method of esterification is used for the preparation of BOC-D-Glu-a- -butyl-Y-methyl diester in the synthesis of (27) ... 

A different strategy providing access to linear polyesters derived from fatty acids in which their aliphatic sequences dangle from macromolecular chains (i.e., a type of structure very different to that of linear PE) has been described recently [73]. Various saturated fatty acid methyl esters were malonated to the corresponding methyl diesters, which were polymerised by transesterification with 1,6-hexanediol (Scheme 4.17). 

The research team of Cramail adopted a similar strategy to prepare aliphatic diols containing monoester, diester, ester-amide, monoamide and diamide linkages from methyl 10-undecenoate derivatives [15]. Resulting diols were condensed with a methyl diester, obtained by the self-metathesis of methyl 10-undecenoate, in the presence of TBD as a transesterification catalyst. This strategy lead to various fully aliphatic polyesters and polyester-amides with Mn values of 6-19 kDa, a glass transition temperature (Tg) below room temperature (RT) and T of 22-127 °C. 

Write equations showing how 3 methyl 1 5 pentanediol could be prepared from a dicarboxylic acid or a diester I... 

Esters. Neopentyl glycol diesters are usually Hquids or low melting soflds. Polyesters of neopentyl glycol, and in particular unsaturated polyesters, are prepared by reaction with polybasic acids at atmospheric pressure. High molecular weight linear polyesters (qv) are prepared by the reaction of neopentyl glycol and the ester (usually the methyl ester) of a dibasic acid through transesterification (37—38). The reaction is usually performed at elevated temperatures, in vacuo, in the presence of a metallic catalyst. 

The Hantsch pyridine synthesis provides the final step in the preparation of all dihydrop-yridines. This reaction consists in essence in the condensation of an aromatic aldehyde with an excess of an acetoacetate ester and ammonia. Tlie need to produce unsymmetrically subsrituted dihydropyridines led to the development of modifications on the synthesis. (The chirality in unsymmetrical compounds leads to marked enhancement in potency.) Methyl acetoacetate foniis an aldol product (30) with aldehyde 29 conjugate addition of ethyl acetoacetate would complete assembly of the carbon skeleton. Ammonia would provide the heterocyclic atom. Thus, application of this modified reaction affords the mixed diester felodipine 31 [8]. 

A solution of 88.5 parts of L-phenylalanine methyl ester hydrochloride in 100 parts of water is neutralized by the addition of dilute aqueous potassium bicarbonate, then is extracted with approximately 900 parts of ethyl acetate. The resulting organic solution is washed with water and dried over anhydrous magnesium sulfate. To that solution is then added 200 parts of N-benzyloxycarbonyl-L-aspartic acid-a-p-nitrophenyl, -benzyl diester, and that reaction mixture is kept at room temperature for about 24 hours, then at approximately 65°C for about 24 hours. The reaction mixture is cooled to room temperature, diluted with approximately 390 parts of cyclohexane, then cooled to approximately -18°C in order to complete crystallization. The resulting crystalline product is isolated by filtration and dried to afford -benzyl N-benzyloxycarbonvI-L-aspartyl-L-phenylalanine methyl ester, melting at about 118.5°-119.5°C. 

For example. 2-ethoxyindole (1 a) with the alkyne diester in refluxing dioxane yields dimethyl 2-ethoxy-3//-l-benzazepine-3,4-dicarboxylate (2) as a minor product along with a 50 % yield of a mixture of the cis- and tran.v-indol-3-ylacrylates 3.20 However, with 2-ethoxy-l-methylindole (1 b) the l//-l-benzazepine 4 becomes the major product. An analogous reaction with l,2-bis(trifluoromethyl)acetylene to yield 2-ethoxy-l -methyl-3,4-bis(trifluoroiriethyl)-1 //-1-benzazepine has been performed however, the yield was not reported.142... 

Hie reaction of a diamine with a diester under anhydrous conditions is reasonably rapid. However, a side reaction at high temperatures (>200°C) is N-substitution. Unfortunately, this N-substitution is particularly strong with methyl esters,28 37 65 and therefore, methyl esters such as dimediyl terephthalate or dimedryl isoph-thalate cannot be used for thermal polyamidations. Other esters, such as ethyl, butyl, and phenyl ester, do not seem to have this problem. 

Allyl- -diathylester 204 Allyl-(2-methyl-allyl)- -diathylester 202 -amid-nitril (2,2-disubst.) 113 Amino- -diathylester 613 Benzyl- -diathylester 204, 208, 210 Benzyl- -dinitril 559 Benzyliden- -diathylester 208, 210 Benzyliden- -diathylester-nitril 206 Benzyliden- -dinitril 559, 643 ter.-Butyl- -nitril 114 Cyclohexyl- -athylester-nitril 206 Cyclohexyl- -diathylester 204 Cyclohexyl- -dinitril 559 Cyclohexyliden- -athylester-nitril 206 Cyclohexyliden- -dinitril 559 (1-Cyclopropyl-athyliden)- -dinitril 666 Diathyl- -amid-nitril 113 -diester 640... 

In the case of the reaction of 2-vinylindole (83, R = Ri = H) with methyl propynoate, a diester is obtained by a multiple one-pot process involving two molecules of the dienophile and the extrusion of ethene (Equation 2.23). 

The electrolysis of methyl adipate in the presence of butadiene has received considerable attention, because it makes long chain diacids easily accessible. A total yield of 96% diester has been claimed for this reaction (Table 8, No. 7). 

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