Synthesis of meta-Functionalized Pyridines by Selective Dehydrogenative Heterocondensation of β- and γ-Amino Alcohols

Abstract

New reactions that convert alcohols into important classes of compounds are becoming increasingly important as their development contributes to the conservation of our fossil carbon feedstock and the reduction of CO₂ emissions. Two key catalytic alcohol conversion concepts are borrowing hydrogen or hydrogen autotransfer and acceptorless dehydrogenative condensation. Herein, we combined both concepts to synthesize meta-functionalized pyridines. First, diols and amines were linked to β-amino alcohols, which can then undergo a selective dehydrogenative heterocondensation with γ-amino alcohols. Iridium catalysts stabilized by PN₅ P pincer ligands that were developed in our laboratory mediate the reactions most efficiently. All of the 3-aminopyridines that we describe in this paper have been synthesized for the first time, emphasizing the degree of innovation of this method and the problems associated with the synthesis of such meta-functionalized pyridines.

Keywords: PNP ligands; amino alcohols; dehydrogenative heterocondensation; iridium; pyridines.