Trimethylsilyl Trifluoromethanesulfonate-Promoted Cyclocondensation of β-Ketoenamides and Subsequent Nonaflation to Pyrid-2-yl and Pyrid-4-yl Nonaflates as Flexible Precursors for Polysubstituted Pyridines

Dedicated to Professor Ernst Schaumann on the occasion of his 70th birthday

Abstract

The intramolecular condensation of β-ketoenamides to 2- and/or 4-pyridone derivatives using either KOt-Bu or trimethylsilyl trifluoromethanesulfonate/Hünig’s base was investigated. Subsequent nonaflation of the cyclization products allowed a facile purification and further functionalization through Suzuki–Miyaura couplings leading to new highly substituted pyridine derivatives. The dependence of the regioselectivity of cyclocondensation on the structure of the β-ketoenamides is discussed.

Key words

enamides - pyridines - cyclocondensation - nonaflates - cross couplings

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