Esters dicarboxylate

The Diels-Alder Reaction consists in the direct combination of a compound containing a conjugated diene system u ith a reagent which possesses a double or triple bond activated bj suitable adjacent groups. Examples of such reagents are maleic anhydride, p-benzoquinone, acraldehyde and acetylene dicarboxylic esters. Combination always occurs at the 1,4 positions of the diene system ... 

The thermal ring opening of l,2-bis(trimethylsiIoxy) cyclobutenes (from acyloin condensation of 1,2-dicarboxylic esters) was used in ring expansion prodecures (see p. 53f.). 

Some straightforward, efficient cyclopentanellation procedures were developed recently. Addition of a malonic ester anion to a cyclopropane-1,1-dicarboxylic ester followed by a Dieckmann condensation (S. Danishefsky, 1974) or addition of iJ-ketoester anions to a (l-phenylthiocyclopropyl)phosphonium cation followed by intramolecular Wittig reaction (J.P, Marino. 1975) produced cyclopentanones. Another procedure starts with a (2 + 21-cycloaddition of dichloroketene to alkenes followed by regioselective ring expansion with diazomethane. The resulting 2,2-dichlorocyclopentanones can be converted to a large variety of cyclopentane derivatives (A.E. Greene. 1979 J.-P. Deprds, 1980). 

The only recorded synthesis of this type from a pyridazine involves the [4 + 2] cycloaddition of the lactim ether (374) with l,2,4,5-tetrazine-3,6-dicarboxylic ester, which proceeds with loss of nitrogen and methanol from the intermediate adduct to give the pyrido[2,3-t/]pyridazine (375) (77AP936). 

Reversible interaction of the carbonyl group with an azine lone-pair (cf. 245) should facilitate substitution adjacent to the heteroatom by the anion of a )3-hydroxyethyl ketone. A similar cyclic intermediate (246) is presumably responsible for the cyclization of acetylene dicarboxylic esters with azines. Similar cyclic intermediates... 

For the ordinary Diels-Alder reaction the dienophile preferentially is of the electron-poor type electron-withdrawing substituents have a rate enhancing effect. Ethylene and simple alkenes are less reactive. Substituent Z in 2 can be e.g. CHO, COR, COOH, COOR, CN, Ar, NO2, halogen, C=C. Good dienophiles are for example maleic anhydride, acrolein, acrylonitrile, dehydrobenzene, tetracya-noethylene (TCNE), acetylene dicarboxylic esters. The diene preferentially is of the electron-rich type thus it should not bear an electron-withdrawing substituent. 

Triphenylphosphine gives Michael additions to the activated triple bond of acetylene dicarboxylic esters in presence of acidic compounds HY (Scheme 1). The reactions take place easily at room temperature, even at -10°C [1], through formation of intermediate activated vinylic phosphonium salts, which undergo a subsequent Michael addition of HY. The reactions afford various stabilized ylides which can be isolated in high yields or undergo possibly evolution, for example by intramolecular Wittig reaction [2]. 

A related preparation of specific stabilized phosphonium yUdes corresponds to the reaction of triarylphosphines with acetylene dicarboxylic esters in presence of fullerene, which affords a cyclopropanyl-fullerene substituted stabilized phosphonium ylide [9] or the corresponding evolution products [10]. 

Preparation by Addition of Tertiary Phosphine Oxides to Acetyiene Dicarboxylic Esters... 

Pyridazine-3,6-dicarboxylate esters react with electron-rich alkenes to give adducts that undergo subsequent elimination to give terephthalate derivatives.317... 

Figure 11 The l,3-dithiole-2-thione-4,5-dicarboxylic ester 1 1.5 adduct with IBr...

Table 15.15 Hydrogenation of dicarboxylic esters under similar conditions.a)...

Toad bufadienolides occur not only by themselves but also in a conjugated form, sulfates, dicarboxylic esters and amino acid-dicarboxylic acid esters have all been reported (Steyn and van Heerden 1998). Because of the activity of the bufadienolides in inhibiting active monovalent cation transporters, it is suggested that these compounds have a role in maintaining sodium homeostasis in toads that migrate between fresh and salt water environments (Flier, I idwards, Daly and Myers 1980). 

Synthetic routes to the title ring system using two other reagents, acetylene dicarboxylic ester and 2,4-dinitro-chlorobenzene, are shown in Scheme 28. Reaction of 145 with DMAD (or its ethyl analogue) yields a ring-closed... 

In the case of the dicarboxylic esters of adipic and pimelic acids, intramolecular condensation gives cyclic esters of /8-keto-carboxylic acids (Dieckmann) ... 

Esters of succinic acid condense to esters of succinylsuccinic acid (1 4-diketohexamethylene-2 5-dicarboxylic esters). Study Baeyer s work on the hydrogenated derivatives of benzene, based on this synthesis. 

The product of the reaction may be still further broken down by eliminating the second carboxyl group. (Preparation of cyclobutane from the dicarboxylic ester formulated above.)... 

To rationalize the stereospecificity of PLE toward a large variety of monocarboxylic and dicarboxylic esters, Tamm and co-workers have proposed the general formula displayed in Fig. 7.5 [5 5] [67]. Here, no representation of the active site is implied, but the model does rationalize numerous data and allows some qualitative predictions. A qualitative topographical model of the active site of PLE has been proposed by Jones and co-workers [68] [69], As shown in Fig. 7.6, substrate binding is defined by a carboxylate group that interacts with the catalytic serine residue, and by one or two hydrophobic groups that bind to sites 1 and/or 2. 

Schildberg and Fleckenstein observed that calciumantagonists can advantageously influence the peripheric vessels and those of the heart.With the 4-aryldihydropyridine-3,5-dicarboxylic esters 4 (Scheme 1.1) that have such effects, the first pharmaceutical products synthesized by Hantzsch reactions were independently introduced by the Bayer and Smith Cline French. ... 

Scheme 1.1 Hantzsch synthesis of 4-aryldihydropyridine-3,5-dicarboxylic esters.

The solvent present in biphasic reactions can still have an effect on the enzyme even though the enzyme functions primarily in an aqueous microenvironment. A particularly dramatic example is the lipase AH (lipase from Burkholderia cepac/fl)-catalysed desym-metrization of prochiral 1,4-dihydropyridine dicarboxylic esters, where either enantiomer can be accessed in high enantioselectivity by using either water-saturated cyclohexane or diisopropyl ether (DIPE) respectively (Scheme 1.60). The acyl group used in acylation and deacylation can also have a dramatic effect on enantioselectivity. " ... 

Scheme 1.60 Resolution of a prochiral 1,4-dihydropyridine dicarboxylic ester with lipase AH in the presence of cyclohexane or DIPE...

Formation of cycloalkane-1,2-dicarboxylate esters by reduction of dibromoalkanedicarboxylate esters at a platinum cathode in tetrahy-drofuran. Data from ref. [109]... 

Today the coupled product is described as being formed by union of two alkyl radicals fonned by loss of one electron and carbon dioxide from the carboxylate ion. Extensive early use of the Kolbe reaction was made for the synthesis of long chain a,co-dicarboxylate esters starting from the half esters of shorter chain a,03-diacids [49]. 

Tire aldehyde has been shown to be an intermediate in reduction of aromatic esters in both acid [149] and alkaline solutions [148]. It can be trapped in good yield in the form of an acetal by reduction of benzoate esters in acetonitrile in the presence of chlorotrimethylsilane [150]. Intermediates in the reduction of diphcnyl-2,2 -dicarboxylate esters undergo a cyclization reaction to form 5,6-dthydroxyph-enanthrene [148]. 

Acetylene dicarboxylic esters and (less easily) acetylene monocarboxylic esters replace nitriles from the 4,5-positions of 1,2,4,3-triazaphosphole rings (92) to give carboxyl derivatives of 1,2,3-diazaphospholes, presumably by a cycloaddition/cycloreversion mechanism, R/R = Me/Ph, SiMej/NMCj <83ZN(B)1484>. 

The products from l,3,2-diazasilacyclopent-4-enes (107 R = Bu , 2,6-Mc2C6H4) and TCNE or acetylene dicarboxylic esters result from cleavage of initial (2- -2) cycloadducts which are isolable in the case of (107 R = Bu ) and the acetylenic ester <87CB795>. 

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