Carboxylate salt alkylations

Carboxylate salt Alkyl halide Catalyst % Yield Ref. 

In addition to providing fully alkyl/aryl-substituted polyphosphasenes, the versatility of the process in Figure 2 has allowed the preparation of various functionalized polymers and copolymers. Thus the monomer (10) can be derivatized via deprotonation—substitution, when a P-methyl (or P—CH2—) group is present, to provide new phosphoranimines some of which, in turn, serve as precursors to new polymers (64). In the same vein, polymers containing a P—CH group, for example, poly(methylphenylphosphazene), can also be derivatized by deprotonation—substitution reactions without chain scission. This has produced a number of functionalized polymers (64,71—73), including water-soluble carboxylate salts (11), as well as graft copolymers with styrene (74) and with dimethylsiloxane (12) (75). 

Low surface energy substrates, such as polyethylene or polypropylene, are generally difficult to bond with adhesives. However, cyanoacrylate-based adhesives can be effectively utilized to bond polyolefins with the use of the proper primer/activa-tor on the surface. Primer materials include tertiary aliphatic and aromatic amines, trialkyl ammonium carboxylate salts, tetraalkyl ammonium salts, phosphines, and organometallic compounds, which are initiators for alkyl cyanoacrylate polymerization [33-36]. The primer is applied as a dilute solution to the polyolefin surface, solvent is allowed to evaporate, and the specimens are assembled with a small amount of the adhesive. With the use of primers, adhesive strength can be so strong that substrate failure occurs during the course of the shear tests, as shown in Fig. 11. 

The anodic oxidation of the carboxylate anion 1 of a carboxylate salt to yield an alkane 3 is known as the Kolbe electrolytic synthesis By decarboxylation alkyl radicals 2 are formed, which subsequently can dimerize to an alkane. The initial step is the transfer of an electron from the carboxylate anion 1 to the anode. The carboxyl radical species 4 thus formed decomposes by loss of carbon dioxide. The resulting alkyl radical 2 dimerizes to give the alkane 3 " ... 

Especially for large-scale work, esters may be more safely and efficiently prepared by reaction of carboxylate salts with alkyl halides or tosylates. Carboxylate anions are not very reactive nucleophiles so the best results are obtained in polar aprotic solvents45 or with crown ether catalysts.46 The reactivity order for carboxylate salts is Na+ < K+ < Rb+ < Cs+. Cesium carboxylates are especially useful in polar aprotic solvents. The enhanced reactivity of the cesium salts is due to both high solubility and minimal ion pairing with the anion 47 Acetone is a good solvent for reaction of carboxylate anions with alkyl iodides48 Cesium fluoride in DMF is another useful... 

As noted in the preceding section, one of the most general methods of synthesis of esters is by reaction of alcohols with an acyl chloride or other activated carboxylic acid derivative. Section 3.2.5 dealt with two other important methods, namely, reactions with diazoalkanes and reactions of carboxylate salts with alkyl halides or sulfonate esters. There is also the acid-catalyzed reaction of carboxylic acids with alcohols, which is called the Fischer esterification. 

PP Pfeffer, LS Silbert. Esterification by alkylation of carboxylate salts. Influence of steric factors and other parameters on reaction rates. J Org Chem 41, 1373, 1976. 

An extension of the Barbier reaction to carboxylates salts [90] affords a simple access to furanyl ketones [91]. By sonication of a mixture of a lithium carboxylate, an alkyl chloride and lithium in THE at room temperature, the intermediate organolithium reagent forms rapidly, then generates the 2-furanyl lithium which adds to the carboxylate group in high yields. The method constitutes an example of a reaction cascade , in which several intermediates are generated sequentially (Scheme 3.13). 

We have previously seen (0-96) that dianions of carboxylic acids can be alkylated in the a position. These ions can also be acylated on treatment with a carboxylic ester1705 to give salts of p-keto acids. As in 0-96, the carboxylic acid can be of the form RCH2COOH or RR"CHCOOH. Since p-keto acids are so easily converted to ketones (2-40), this is also a method for the preparation of ketones R COCHiR and R COCHRR", where R can be primary, secondary, or tertiary alkyl, or aryl. If the ester is ethyl formate, an a-formyl carboxylate salt (R = H) is formed, which on acidification spontaneously de-carboxylates into an aldehyde.1706 This is a method, therefore, for achieving the conversion RCH2COOH — RCH2CHO, and as such is an alternative to the reduction methods discussed in 0-83. When the carboxylic acid is of the form RR CHCOOH. better yields are obtained by acylating with acyl halides rather than esters.1707... 

From carboxylate salts and alkyl halides RC02Na + R X — RC02R + NaX Restricted to primary halides with high Sn2 reactivity. 

The thermodynamic stability of the binuclear site has been demonstrated by the spontaneous assembly of [Fe20(02CR)2L2] (13) from ferric salts in the presence of water, an alkyl carboxylate salt, and a tridentate nitrogen donor ligand L that can cap an octahedral face on iron (8). Suitable ligands include tris(pyrazolyl)borates and 1,4,7-triazacyclononanes. Structure (13) is in essence a portion of the basic ferric acetate structure. The complexes are excellent physical and structural models of the diiron sites and model some aspects of reactivity including redox activity and interconversion of the oxo and hydroxo bridge. 

Two different types of coupling processes have been cited for pyridine. The first involves the carboxylation and subsequent alkylation of the carboxylate salt to form the 1,4-dihydro-1,4-dicarboxyalkyl product (6). Reductive carboxylation of 2,2 -bipyridyl (1) followed a slightly different pathway, giving the l,4-dihydro-4,5-dicarboxyethyl product (7).36 Apparently, steric factors favor electrophilic attack on the / carbon. 

Alcohols are capable of being converted to metal salts, alkyl halides, esters, aldehydes, ketones, and carboxylic acids. 

These are the most favourable of all and the precursors, such as the hydroxy acids, e.g. 15, cannot usually be isolated, though the carboxylate salts are stable. The only important thing is to get the oxidation level of the precursor right. Using cyclic amines as examples, a fully saturated ring 45 would come from an alkylation reaction on 46 X = a leaving group. Imines 47 or enamines 49 would come from aldehydes or ketones 48. 

An intramolecular 2-alkylation was also observed in a sulfonyl free radical induced addition-cyclization <95SL763>. A key intermediate in a new synthesis of pallescensin A (a biologically active labdane diterpene) was prepared by a cationic cyclization reaction with a furan <95SYN1141>. The sonochemical Barbier reaction was extended to carboxylate salts. 2-Furanylketones 10 can be obtained by sonication of a mixture of furan, lithium carboxylate, an alkylchloride, and lithium in THF <95JOC8>. 

Sodium thiosulfate reacts with alkyl halides to form salts of the type RSSOjNa (Bunte salts). Alkyl disulfides may be obtained from these salts by pyrolysis or reaction with iodine or hydrogen peroxide. The yields range from 47% to 6S>%. Cyano and carboxyl groups do not interfere. Benzoylation of sodium thiosulfate produces benzoyl disulfide in 58% yield. ... 

Alkylation of potassium enolates is not always fruitful, and so counterion exchange with lithium bromide prior to addition of the electrophile has been recommended. Reduction of aromatic esters instead of acids provides a number of potential advantages. The esters tend to be more soluble than carboxylate salts, hydrogenolysis of 2-alkoxy substituents does not appear to present the s me problem, and the products are more stable. This can be important when enol ether functions are generated, allowing the necessarily acidic work-up procedures for carboxylic acids to be avoided. Indeed, the hydrolysis of enol ether functions may be very slow in aqueous acid and is best achieved through catalysis by mercury(II) nitrate. ... 

Other leaving groups can also be replaced by OCOR. Alkyl chlorosulfites (ROSOCl) and other derivatives of suffuric, sulfonic, and other inorganic acids can be treated with carboxylate ions to give the corresponding esters. Treatment with oxalyl chloride allows displacement by carboxylate salts.The use of dimethyl... 

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