Carboxylic acids and active

The following compounds with H—C and II—M bonds undergo oxidative addition to form metal hydrides. This is examplified by the reaction of 6, which is often called ortho-metallation, and occurs on the aromatic C—H bond at the ortho position of such donar atoms as N, S, 0 and P. Reactions of terminal alkynes and aldehydes are known to start by the oxidative addition of their C—H bonds. Some reactions of carboxylic acids and active methylene compounds are explained as starting with oxidative addition of their O—H and C—H bonds. 

Nickel and palladium complexes also catalyze the reaction of 1,3-butadiene with compounds containing active hydrogen such as alcohols, amines, carboxylic acids, and active methylene and methyne compounds [equations (13.90)-(13.94)]. The mechanism... 

Carboxylic acid esters from carboxylic acids and active halides s. 12, 286 Cyanomethyl esters s. 12, 463 COOH COOR... 

The reaction proceeds via the formation of a first chiral zwitterionic intermediate from pivaUc anhydride and the amidine-based catalyst A mixed anhydride is then generated in the presence of the racemic carboxylic acid and activated by the chiral acyl-transfer catalyst to form the second zwitterionic intermediate. The latter species selectively reacts with a nucleophilic alcohol to afford the desired enantioenriched carboxyUc ester (Scheme 41.10). 

Fig. 21. Representative nonionic photoacid generators. A variety of photochemical mechanisms for acid production ate represented. In each case a sulfonic acid derivative is produced (25,56,58—60). (a) PAG that generates acid via 0-nitrobenzyl rearrangement (b) PAG that generates acid via electron transfer with phenohc matrix (c) PAG that is active at long wavelengths via electron-transfer sensitization (d) PAG that generates both carboxylic acid and...

Rates of debromination of bromonitro-thiophenes and -selenophenes with sodium thio-phenoxide and sodium selenophenoxide have been studied. Selenophene compounds were about four times more reactive than the corresponding thiophene derivatives. The rate ratio was not significantly different whether attack was occurring at the a- or /3-position. As in benzenoid chemistry, numerous nucleophilic displacement reactions are found to be copper catalyzed. Illustrative of these reactions is the displacement of bromide from 3-bromothiophene-2-carboxylic acid and 3-bromothiophene-4-carboxylic acid by active methylene compounds (e.g. AcCH2C02Et) in the presence of copper and sodium ethoxide (Scheme 77) (75JCS(P1)1390). 

In man, the metabolic pathways of mepirizole were distinct from those in experimental animals, since hydroxylation on each of the aromatic rings did not occur in man. Compound (752) was obtained by oxidation of the 3-methyl group to the carboxylic acid (a similar process occurs with 5-methylpyrazole-3-carboxylic acid, an active metabolite of 3,5-dimethylpyrazole). However, the carboxylic acid metabolite of mepirizole had no analgesic activity and did not decrease blood glucose. 

Neurotropic and antistress properties of 2,4-dimethylpyrido[l, 2-u]pyr-imidinium perchlorate were compared with those of piracetam (95MI7). AH-Pyrido[l,2-u]pyrimidin-4-one binds selectively to rat A3 receptors with a A", value of 48/xM. No affinities were observed to rat Ai and A2 receptors (96MI17). 4-Oxo-4//-pyrido[l,2-u]pyrimidine-3-carboxylic acid and -3-carbonitrile did not exhibit significant antibacterial activities (97MI6). 

Niacin (Fig. 1) is a collective name for all vitamers having the biological activity associated with nicotinamide (= pyridine-3-carboxamide), including nicotinic acid (= pyridine-3-carboxylic acid) and a variety of pyridine nucleotide structures. 

Thionyl chloride is another activating agent employed for reactions between aromatic carboxylic acids and phenols in pyridine solution. The mechanism suggested does not involve the formation of an acid chloride but assumes the existence of an intermediary mixed sulfinic anhydride which undergoes reaction with phenolic endgroups (Scheme 2.32).311... 

Most resolution is done on carboxylic acids and often, when a molecule does not contain a carboxyl group, it is converted to a carboxylic acid before resolution is attempted. However, the principle of conversion to diastereomers is not confined to carboxylic acids, and other groupsmay serve as handles to be coupled to an optically active reagent. Racemic bases can be converted to diastereomeric salts with active acids. Alcohols can be converted to diastereomeric esters, aldehydes to diastereomeric hydrazones, and so on. Even hydrocarbons can be converted to diastereomeric inclusion... 

Resting cells of A. nicotianae FI1612 also catalyzed the carboxylafion of 2-methylindole and quinoxaline. The activities toward 2-methylindole and quinoxaline were 37 and < 1% of the activity toward indole, respectively. The reaction products of the reverse carboxylafion, indole-3-carboxylic acid and 2-methylindole-3-carboxylic acid, were isolated and identified through physicochemical analyses with the authentic compounds as reference. 

Nucleophilic substitutions of 0-activated 2-hydroxy carboxylic acids and esters, respectively, are well established, but little is known about the analogous reactions of activated cyanohydrins. Chiral 2-sulfonyloxynitriles, accessible from non-racemic cyanohydrins, have a relatively high configurational stability. They react with nucleophiles under very mild conditions under inversion of configuration (Scheme 8). ° ... 

In the sixth chapter the activation of O-H bonds of water, alcohols and carboxylic acids, and their addition to multiple bonds is reported. Since the formally oxidative addition of ROH gives rise to hydrido(hydroxo) complexes, [MH(OR)Ln] which are postulated as intermediates in many important reactions (water gas shift reaction, Wacker-chemistry, catalytic transfer hydrogenations etc.) the authors of this chapter,... 

Ketones can also be prepared directly from carboxylic acids by activation as mixed anhydrides by dimethyl dicarbonate.236 These conditions were used successfully with alkanoic and alkanedioic acids, was well as aromatic acids. 

Direct hydrogenation of amino acids to amino alcohols was first examined by Adkins et al. (3) via the esters, and recently studied by Antons and Beitzke in patents (4). Using Ru/C catalysts at high pressures (>14 MPa) and mild temperatures (70-150 °C), Antons demonstrated the conversion of carboxylic acids and amino acids with retention of optical activity in the product alcohols. High yields (>80%) and high enantiomeric purity (>97% in many cases) were achieved. Broadbent et al. had demonstrated earlier that under certain conditions hydrogenation of amino acids can be accompanied by deamination (8). 

Seifert, W.K. Effect of Phenols on the Interfacial Activity of Crude Oil (California) Carboxylic Acids and the Identification of Car-bazoles and Indoles, Anal. Chem. 1969, 41, 562. 

Hydrogenolyses of carboxylic acids and esters to the corresponding aldehydes seems very attractive due to their simplicity. Copper chromites are the most widely used catalysts.15 Raney copper and zinc oxide-chromium oxide have also been used for this process.16-18 The hydrogenolysis of methyl benzoate to benzaldehyde was studied on various metal oxides at 300-350°C. ZnO, Zr02 and Ce02 presented high activities and selectivities (Scheme 4.8). 

Nitrilases convert nitriles to the corresponding carboxylic acids and NH3 through a cysteine residue in the active site [50]. Because of their high enantio- and regio-selectivity, nitrilases are attractive as green catalysts for the synthesis of a variety of carboxylic acids and derivatives (Figure 1.10) [51,52]. Recently, a number of recombinant nitrilases have been cloned and characterized heterologously for synthetic applications [50,53,54]. 

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