Additives esters

This behavior is consistent with an autocatalytic process, whereby the liberated carboxylic end groups catalyze the cleavage of additional ester groups (Eq. 3) ... 

Examples of this approach to the synthesis of ketones and carboxylic acids are presented in Scheme 1.4. In these procedures, an ester group is removed by hydrolysis and decarboxylation after the alkylation step. The malonate and acetoacetate carbanions are the synthetic equivalents of the simpler carbanions that lack the additional ester substituent. 

Processes devised to make cotton hydrophobic are summarised in Table 10.42. These processes are undoubtedly successful in conferring substantivity for disperse dyes but attaining compatibility within a range of dyes across the entire colour gamut and on fibre blends of various blend ratios could be a problem. In addition, ester bonds can be saponified... 

The isomerization of the smallest alkynes 80 with halogens in a propargylic position has been described for chlorine [151, 152], bromine [153] and iodine [154] (Scheme 1.35), but often might proceed by an SN2 -type substitution rather than a prototropic rearrangement [155-159]. On the other hand, transformations such as 82 —> 83 [160] or 84 —> 85 [161] are clearly prototropic (Scheme 1.36). This is also true for propargylic halides such as 86 with its additional ester group assisting the prototropic isomerization [162,163] (Scheme 1.37). 

The competition between a propargylic ether and a teriary propargyhc amine provided an allenyl ether rather than an allenylamine [182], The reaction was also successful with propargyl allyl ethers [232]. An additional ester group in the propargylic position is tolerated [233], and consequently the reaction also works with esters of propargyhc alcohols [234—236]. In the past 4years, several derivatives of carbohydrates were converted successfully [217, 237-241] two examples are the isomeriza-tions of enantiomerically pure 98 [242] and 100 [217, 243] (Scheme 1.43). 

Woodward et al. have used the binaphthol-derived ligand 40 in asymmetric conjugate addition reactions of dialkylzinc to enones [46]. Compound 40 has also been studied as a ligand in allylic substitutions with diorganozinc reagents [47]. To allow better control over selectivity in y substitution of the allylic electrophiles studied, Woodward et al. investigated the influence of an additional ester substituent in the jS-position (Scheme 8.25). 

The secondary amide can also attack intramolecularly an additional ester function to form a cyclic imide, although only in moderate yields [67], Finally, the palladium-catalysed intramolecular reaction with an alkyne, resulting in a hydro-amination of the latter, will be described later (Fig. 17) [68]. 

Fig. 22 Lactams formed by cyclization of an additional nitrogen into an additional ester...

Additional ester monomers convertible into homopolymers were prepared by Taniguchi et al. (4) and are discussed. 

One method that uses none of the above catalysis is worthy of mention, the diazomethane method. This method is very useful if there is only a very limited amount of free fatty acids as the starting material, since no extraction is needed before the resulting FAME can be injected into the GC for analysis. The authors of this unit have never performed this method. Interested readers can learn more from information presented elsewhere (Christie, 1989b). In addition, esters other than methyl may be required from time to time for specific purposes, and this is beyond the scope of the present discussion. 

In addition, esters of dextran-bearing palmitoyl groups and phosphate functions can be used for the preparation of specifically modified liposomes, which are exploited for the entrapment of peptides such as hirudin, the most potent inhibitor of thrombin [105]. 

Two main problems restricted the synthetic usefulness of the sulfinyl male-ates, the low regioselectivity of the elimination of the sulfinyl group in reactions with 1-substituted dienes, and its moderate reactivity (almost identical to that of the sulfinyl acrylates, despite the additional ester group). The use of TiCl4 overcame the second problem, but this catalyst is not compatible with alkoxy substi-... 

Dieckmann procedure unfortunately does not permit wide latitude in the number and nature of additional functional groups which can be tolerated. The effective synthesis of 7 7 denotes that an additional ester substituent may be tolerated.37 ... 

Other Uses. Reagent 1 has been used for enantioselec-tive enolborination, albeit with poor (1.1 1) selectivity. Similar bis-sulfonamide-derived boron Lewis acids have been used for aldol additions, "" ester-Mannich reactions, Diels-Alder reactions, Ireland-Claisen reactions, and [2,3]-Wittig rearrangements. Similar bis-sulfonamide-derived aluminum Lewis acids have been used for aldol additions, Ehels-Alder... 

Under acidic conditions, however, the liberation of free acetic acid during hydrolysis of the esters can increase the acidity and enhance further hydrolysis of not only additional ester groups, but acetal linkages and lignin bonds as well. A prime example is the so-called autohydrolysis reaction (2) in which acetic acid liberated by steam can cause complete hydrolysis of the hemicelluloses and convert the lignin into soluble fragments. 

A solution to this problem was to use the so-called double-e.ster approach, in which an additional ester or carbonate... 

The synthesis of dihydrofurans with an additional ester moiety and one or two quaternary centers are prepared from titanium enolates formed by reactions of 3,4-dienoates with Cp2TiCl2. Titanium enolate derivatives TiCl3[CH2CH2C(=0)0Et] and the Tebbe reagent compound have been applied in the synthesis of pumilio-toxin.1915 Chiral allyl and mono-Gp chloro enolato titanium compounds add with high enantioface discrimination to aldehyde.973... 

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