Carboxylic acids introduction

Carboxyl group (Introduction) Carboxylate ion (5.3) Carboxylic acid (Introduction) Carboxylic acid anhydride (5.5) Carboxylic acid chloride (5.5)... 

The enol content of a carboxylic acid is far less than that of an aldehyde or ketone and introduction of a halogen substituent at the a carbon atom requires a different set... 

And so the skillful selection, introduction, and removal of a total of 12 different protective groups have played a major role in the successful total synthesis of paly toxin carboxylic acid (Figure 1,2). 

Et3SiCl, Pyr. Triethylsilyl chloride is by far the most common reagent for the introduction of the TES group. Silylation also occurs with imidazole and DMF arid with dimethylaminopyridine as a catalyst. Phenols, carboxylic acids, and amines have also been silylated with TESCl. 

TBDMSCl, imidazole, DMF, 25°, 10 h, high yields. This is the most common method for the introduction of the TBDMS group on alcohols with low steric demand. The method works best when the reactions are mn in very concentrated solutions. This combination of reagents also silylates phenols, hydroperoxides, and hydroxyl amines. Thiols, amines, and carboxylic acids are not effectively silylated under these conditions. ... 

The isomeric 4-iodopyrazole-5-carboxylic acid is cyclocondensed in a similar way. Introduction of the additional methyl group into the ring has no effect on the direction of cycloaddition 4-iodo-l,3-dimethylpyrazole-5-carboxylic acid forms only 5-lactones (Scheme 118). 

Because the dissociation of a carboxylic acid is an equilibrium process, any factor that stabilizes the carboxylate anion relative to undissociated carboxylic acid will drive the equilibrium toward increased dissociation and result in increased acidity. An electron-withdrawing chlorine atom, for instance, makes chloroacetic acid (Ka = 1.4 x 10-3) approximately 80 times as strong as acetic acid introduction of two chlorines makes dichloroacetic acid 3000 times as strong as acetic acid, and introduction of three chlorines makes trichloroacetic acid more than 12,000 times as strong. 

Carboxylic acid (Chapter 20 introduction) A compound containing the -C02H functional group. 

Carboxylic acid derivative (Chapter 21 introduction) A compound in which an acyl group is bonded to an electronegative atom or substituent Y that can act as a leaving group in a substitution reaction, RCOY. 

As mentioned in the Introduction, rearrangements of the intermediate alkyl cation in the Koch synthesis may compete with the carbonylation. Under the kinetically controlled conditions prevailing in the Koch synthesis of carboxylic acids, the rearrangements occur only from a less stable to a more stable carbonium ion, e.g. from a secondary to a tertiary ion. The reverse rearrangements—from a more stable to a less stable... 

Further, Wasserman and coworkers developed a direct acylation of stabilized phosphonium ylides by carboxylic acids in presence of the EDCI/DMAP (way c). This last method allows the introduction of a-aminoacid structures into the resulting P-oxo phosphorus ylides [19-25],opening the way to the total synthesis of depsipeptide elastase inhibitors [22,24] or cyclic peptidic protease inhibitor EurystatinA [20]. 

The first non-peptide oxytocin antagonists, based on a spiropiperidine template, were described by Merck in 1992 [68-70]. The binding affinity data for key compounds from this series are summarised in Table 7.2. The initial screening hit, L-342,643, (23), had modest (4/iM) affinity for rat uterine oxytocin receptors and very little vasopressin selectivity [71]. A structure activity relationship (SAR) study was carried out around this template, focussing on the toluenesulphonamide group. This work led to the identification of bulky lipophilic substitution as key to improved oxytocin potency, while the introduction of a carboxylic acid group led to improved... 

Introduction of 3,5-dimethyl and 4-substituent on the Phebox skeleton revealed a weak substituent effect on the degree of asymmetric induction (Scheme 15) [28,29]. When trimethylsilyl acrylate was used as enolate source, the (3-hydroxy carboxylic acid was obtained directly upon mild acid hydrolysis. In the production of carboxylic acid 49, an enantiomeric excess of 96% ee was attained using the NC -substituted Phebox-Rh catalyst. 

End-functional polymers were also synthesized by lipase-catalyzed polymerization of DDL in the presence of vinyl esters [103,104]. The vinyl ester acted as terminator ( terminator method ). In using vinyl methacrylate (12.5 mol % or 15 mol % based on DDL) and lipase PF as terminator and catalyst, respectively, the quantitative introduction of methacryloyl group at the polymer terminal was achieved to give the methacryl-type macromonomer (Fig. 12). By the addition of divinyl sebacate, the telechelic polyester having a carboxylic acid group at both ends was obtained. 

The palladium-catalyzed Heck carbonylation reaction is a powerful means of generating amides, esters, and carboxylic acids from aryl halides or pseudohalides [28]. The development of rapid, reliable, and convenient procedures for the introduction of carbonyl groups is important for the development of high throughput chemistry in general and high-speed microwave-mediated chemistry in particular. Unfortunately, the traditional method of introducing carbon monoxide into a reaction mixture via a balloon or gas tube is not practical because of the special requirements of microwave synthesis. 

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