Acid chlorides via carboxylic acids

Isocyanates from carboxylic acid chlorides via carboxylic acid azides... 

Furanones from 2-acetylenealcohols and carboxylic acid chlorides via carboxylation-decarboxylation... 

The OPLS parameters (charges and Lennard-Jones terms) were obtained primarily via Monte Carlo simulations with particular emphasis on reproducing the experimental densities and heats of vaporization of liquids. Those simulations were performed iteratively as part of the parametrization, so better agreement with experiment is obtained than in previous studies where the simulations were usually carried out after the parametrization. Once the OPLS parametrization was completed, further simulations were also performed in order to test the new set of parameters in the calculation of other thermodynamic and structural properties of the system, besides its density and its heat of vaporization. Parameters have now been generated, among others, for water, alkanes, alkenes, alcohols, amides, alkyl chlorides, amines, carboxylic esters and acids, various sulfur and nitrogen compounds, and nitriles. A protein force field has been established as well. 

Additional work was carried out by the GE group on optimization of the reaction yield and to eliminate unwanted linear oligomers [14], Three side reactions which interfere with synthesis of cyclics were identified reaction of the amine with acid chloride to form an acyl ammonium salt, followed by decomposition to an amide (Equation (3.2)) reaction with CH2CI2 to form a salt (Equation (3.3)) hydrolysis of the acid chloride, forming carboxylate via catalysis... 

The use of DMF to accelerate the formation of acid chlorides from carboxylic acids has been reviewed previously,4 and is believed to occur via an imidoyl chloride intermediate.5... 

Ketenimines are usually prepared from carboxylic acid derivatives such as amides and imino chlorides via elimination and from nitriles via alkylation with alkyl halides under strong basic conditions (21,64). 

Final purification by use of metal complexes was also applied in the syntheses of the ligands XS4—H4. These ligands exclusively contain thiolate donors and were prepared by Hahn et al. (23) using 2,3-dimercaptobenzoic acid as starting material (Scheme 8). Isopropyl or benzyl protection of the thiol functions, conversion into the acyl chlorides, reaction with a,oo-diamines, and deprotection of the sulfur atoms enabled the connection of two 1,2-benzene-dithiol units via carboxylic acid amide bonds. 

Acyl peroxides from carboxylic acids via carboxylic acid chlorides... 

Bromination via carboxylic acid chlorides Halogenocarboxylic acids... 

Activation of Carboxylic Acids Synthesis of Acyl Imidazoles. iV,AA-Carbonyldiimidazole (1) converts carboxylic acids into the corresponding acylimidazoles (2) (eq 1). The method can be applied to a wide range of aliphatic, aromatic, and heterocyclic carboxylic acids, including some examples (such as formic acid and vitamin A acid) where acid chloride formation is difficult. The reactivity of (2) is similar to that of acid chlorides, but the former have the advantage that they are generally crystalline and easily handled. Isolation of (2) is sirr5>le, but often unnecessary further reaction with nucleophiles is usually performed in the same reaction vessel. Conversion of (2) into acid chlorides (via reaction with HCl), hydrazides, hydroxamic acids, and peroxy esters have all been described. Preparation of the more irr5)ortant carboxylic acid derivatives is described below. 

An exception to the definition for pseudo poly(amino acids) as previously established is a polymer synthesized by Chen et al. [31,32], because its backbone is comprised of lysine alternating with an isophthaloyl group and lacks nonamide linkages (Table 12.2). Hydrophobicity of the polymer is increased by conjugating ethanol or hydro-phobic amino acids, such as valine, leucine, and phenylalanine, as protecting groups on the carboxyl terminal of lysine via carbodiimide chemistry. This protected lysine is then copolymerized with isophthaloyl chloride via single-phase polymerization in the presence of a base (Table 12.2) [32]. 

Chlorides from carboxylic acids via benzophenone acyloximes... 

Phosphorus pentachloride is an electrophile, with excellent chloride leaving groups. The carboxylic acid reacts with PCI5 to give an acid chloride, via an activated phosphoryl intermediate. 

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