Microwave-Promoted Syntheses of Pyridine Carboxamides and tert-Carboximides from Novel 6-Acetylpyridine-2-carboxylic Acid

Abstract

A novel 6-acetylpyridine-2-carboxylic acid (4) was obtained occasionally during the synthesis of asymmetric ethyl 6-acetylpyridine-2-carboxylate (3) from 2,6-dipiclinic acid (1). Compounds 3 and 4 could transform mutually under some specific conditions. Two reactions of distinctive types occurred when they reacted with the aromatic amines as precursors, due to different functional groups on the 2-position of pyridine in the molecules of 3 and 4: one was Schiff base condensation and the other was an amidation reaction. From the latter reaction, two series of new compounds, pyridine carboxamides (5a–d) and pyridine tert-carboximides (6a–h), resulted. The relevant reaction mechanism is discussed in detail.

Keywords:

• 6-Acetylpyridine-2-carboxylic acid
• amidation reaction
• microwave irradiation
• reaction mechanism

ACKNOWLEDGMENTS

We are grateful to the Natural Science Basic Research Plan in Shaanxi Province (No. 2009JQ2006), the Scientific Research Plan Projects of Shaanxi Education Department (No. 09JK696), the Natural Science Foundation of Shaanxi Province (No. 2006B17), and the Science and Technology Research Project Foundation of Xi'an Shiyou University (No. Ys29030511) for financial support.

Notes

^a Yield refers to isolated yield.

^b Melting points of compound 6b, 6f, 6g, and 6h are not available.