Dialkyl aminopyridine

The tremendous scope of utilization of DMAP and PPY as catalysts has led to an active interest in the development of their polymeric analogs. The pioneering work was carried out by Hierl et al (8) and Delaney et al. (9). They attached 4-dialkyl-aminopyridine derivatives to poly(ethyleneimine) and found the modified polymers to be highly active catalysts for hydrolysis of p-nitrophenylcarboxylates. Since then, many research groups have reported the synthesis of polymers functionalized with 4-dialkyl-aminopyridine (10-18). 

In summary, among the carbodiimide-based methods only the carbodiimide/dialkyl-aminopyridine technique has been widely used in the synthesis of depsipeptides. It usually affords the desired products in moderate or high yield and has good potential for routine use in the esterification of urethane-protected amino acids or peptide fragments even in the case... 

Pyridylaminomethylenemalonates (262) were prepared in over 90% yields in the reactions of 2-aminopyridines, ethyl orthoformate, and dialkyl malonates at 130°C for 3-6 hr (73GEP2227651 87SC549). 

In the uncatalyzed condensations of 2-aminopyridines, alkyl orthoformate, and dialkyl malonate at 110°C, 2-pyridylaminomethylenemalona-mates (263, R = H, Me R1 = Me, Et) were obtained in 20-25% yields. When isoamyl orthoformate was applied, a 5.2 4.8 mixture of ethyl and isoamyl N-(6-methyl-2-pyridyl)aminomethylenemalonamates (263, = Me, R1 = Et and isoamyl) was isolated in 90% yield (87SC549). 

Iodination of 2-aminopyridine under a variety of experimental conditions gives, in all cases, 2-amino-5-iodopyridine when only one molar equivalent of iodine is used. Yields range as high as 90%.°7,71,89-94 The A-monoalkyl and A,A-dialkyl derivatives behave similarly.92... 

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