Imidate synthesis

These syntheses can be considered as heterocyclic analogue of the poly(ether imide) synthesis... 

Polyamide-6 (PA-6), synthesis of, 174-176. See also PA-6 entries Polyamide endgroups, 161 Poly amide-imide, synthesis of, 291 Polyamides (PAs), 135-193. See also Nylons PA entries acid chloride polymerization of, 155-157... 

Electron-deficient nitriles, such as for instance trichloroacetonitrile and trifluoroacetonitrile (A=B A = N B = CCC13, CCF3), are known to undergo direct and reversible, base-catalyzed addition of alcohols providing O-alkyl trichloroacetimidates (1,50). This imidate synthesis has the advantage that the free imidates can be isolated as stable adducts, which are less sensitive to hydrolysis than their corresponding salts. 

The first publications to describe the phosphane oxide-catalyzed carbodi-imide synthesis from isocyanate appeared in 1962. In this case iminophos-phoranes were recognized as important intermediates. The first mechanistic studies also appeared at this time. Scheme 24 depicts the proposed two-step mechanism (62JA3673, 62JA4288 66CJC2793). 

Mahlin, J.A., Jung, K.H., and Schmidt, R.R., Glycosyl imidates, synthesis of flavone C-glycosides vitexin, isovitexin and isoembigenin, Liebigs Ann. Chem., 3, 461, 1995. 

Heptasulfur imide, synthesis 25 Imidosulfuric acid chloride, synthesis 26 Dialkylsulfamoyl chlorides, synthesis 27 N- and JV,AT -Substituted sulfamides, synthesis 28 Dialkylamides of (trichlorophosphoranylidene)sulfamic acid, synthesis 29... 

Work on improving the thermal resistance and particularly the resistance to carbonization (short circuiting of layers of enameled wires under the influence of temperature) via special glycols led to diphenols [29,30]. Diphenols are not reactive under the conditions of a normal poly(ester-imide) synthesis. In synthesis the lower aliphatic diesters of diphenols were used [29-32]. The use of acid chlorides in the polyester reaction with aromatic OH-groups was also protected by patents [33-35] but it seems unlikely that this reaction was performed on the production scale. 

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