The piperidine ring is present in many medicinal compounds and naturally occurring alkaloids as an important structural feature. This motif includes both simple and annulated piperidines and quinolizidines. More than 12 000 piperidine derivatives were reported in clinical trials in about 10 years period. Conjugate addition reactions of organometallic reagents to N-Boc-4-pyridones will provide a unique and direct entry into 2,3-dihydropyridones that can be highly useful in the synthesis of such piperidine compounds. N-Boc- and N-ethoxycarbonyl-4-pyridones and the resulting 2,3-dihydropyridones undergo unprecedented 1,4-conjugate addition reactions with Grignard reagents without using copper catalysts. The reactions require the use of Lewis acids. To the best of our knowledge, this represents the first example of conjugate additions of Grignard reagents to N-protected-4-pyridones in the absence of copper catalysts.

Unprecedented conjugate addition reactions of Grignard reagents to N-Boc-4-pyridones without Cu(I) catalysts

245th National Meeting (2013)

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