Acid halides amide synthesis

The polyamide and the polyether segments are usually incompatible, phase separation often occurs and the reaction between the reactive chain-ends can only take place at the interface. This reaction can be accelerated by using very reactive functional groups, such as acid halides. The synthesis of polyamides and polyesters via interfacial polymerization has been extensively reviewed by P. W. Morgan [43] in the mid-sixties. A few years later, Castaldo et al. [44] successfully synthesized a poly(ether ester amide) based on PA6.6 and PEO. The a,oj-dihydroxy polyether was first reacted with a diacid chloride for several hours, either in the bulk or in chloroform, and at a rather low temperature (60-90°C). The mixture was then poured into a vigorously stirred aqueous solution of diamine and sodium hydroxide. Later, de Candia et al. [45] reproduced this technique to study the physical and mechanical properties of the copolymer. The same polymerization technique was also used to prepare copolymers based on PPO as the polyether segment and PA6.10 as the polyamide block [3,46,47]. 

Acid halides, also called acyl halides, are activated derivatives used for the synthesis of other acyl compounds such as esters, amides, and acylbenzenes (in the Friedel-Crafts acylation). The most common acyl halides are the acid chlorides (acyl chlorides), and we will generally use acid chlorides as examples. 

At oxidation level 3, acid chlorides occupy a key position, since they may serve as a nearly universal substrate for an isohypsic transformation into any kind of carboxylic acid derivative. Acid halides are electrophiles that are synthetically equivalent to acyl cations (RCO ). In this capacity they are used for the synthesis of such important compounds as esters, amides (and hence, nitriles), thioesters, etc. (see Scheme 2.57), and for the formation of C-C bonds in the Friedel-Crafts reaction (see above). Acid chlorides may readily lose HCl upon treatment with triethylamine. This isohypsic conversion leads to ketenes, important reagents widely employed in [2 + 2] cycloadditions, as we will see later. 

Conductivity measurements have revealed that DMF and carboxylic acid chlorides form salt-like adducts (22) in an equilibrium reaction (equation 12). Such adducts can be prepared either from DMF and acid halides (chlorides and bromides) or from chloromethyleneiminium salts and salts of carboxylic acids. Acyloxyiminium salts (23) can be prepared in the pure state by reacting acid amides with carboxylic acid chlorides in the presence of silver trifluoromethanesulfonate (equation 13). Salts of type (24 equation 14) are regarded as being intermediates in the synthesis of ketones from carboxylic acids and Grignard reagents in the presence of a-chloroenamines as well as in the preparation of acyl halides (F, Cl, Br, I) by action of a-haloenamines on carboxylic acids. ... 

Pinner synthesis of orthoesters starting from alkoxymethyleneiminium salts (410 equation 192) (imino ester hydrohalides) is a standard procedure, which has been reviewed several times.For some more recent results see ref. 7. Closely related to this reaction is the alcoholysis of IV-alkyl- and NJ -di-alkyl-alkoxymethyleneiminium salts or acid amide-acid halide adducts. Orthoesters are formed via N//-dialkylalkoxymethyleneiminium salts when amide acetals (411 Scheme 74) are alcoholyzed in the presence of acetic acid. - ... 

Phosphanes are widely used as reagents in organic synthesis, triphenylphos-phane being the most commonly applied due to its stability towards oxidation. The polymer-supported analog has so far found use in the transformation of alcohols into alkyl halides and acids into acid halides, using either carbon tetrachloride or carbon tetrabromide as the halogen source (Scheme 6.4) [7, 11-14], This system can also successfully transform primary amides and oximes into nitriles, whereas secondary amides are transformed into imidoyl chlorides (Scheme 6.5) [15],... 

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