synopsisThe mechanism of cure has been studied in coating systems comprising blends of ammonium salts of acrylic acid-acrylic ester copolymers and alkoxymethylmelamines.Experiments were conducted both on the resin components themselves and on model compounds having analogous chemical structures. Curing of the resin begins with loss of ammonia to regenerate free carboxyl groups, rather than loss of water to form amides.The allcoxy group is eliminated, and ester crosslinks are formed between the carboxyl and the methylolmelamine. Base binding studies on cured films show that the extent of crosslinking depends on the exact composition of the resin system and the presence or absence of an acidic catalyst. These variables can be adjusted to provide essentially quantitative crosslinking in the cured coating, as shown by the complete disappearance of unreacted carboxyl groups.
An enantiospecific 1,2-amine migration process through an aziridinium intermediate involving ring-opening with potassium phthalimide derivatives to produce precursors to drug candidates was developed. The precursor amine derivatives were readily available by epoxide opening of simple glycidyl ether derivatives. The regioselectivity of the process was shown to provide approximately 85% of the desired rearranged product with subsequent conversion to the desired drug candidate occurring with excellent purity. An alternative approach using the same glycidyl ether derivatives as starting materials that overcame this regiochemical limitation was subsequently demonstrated.
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