A novel strategy has been established to assemble an array of densely substituted pyridine derivatives from nitriles and o-substituted aryl alkynes or 1-methyl-1,3-enynes via a non-classical [4 + 2] cycloaddition along with 1,5-hydrogen shift process. The well-balanced affinities of two different alkali metal salts enable the C(sp3)-H bond activation as well as the excellent chemo- and regioselectivities. This protocol offers a new guide to construct pyridine frameworks from nitriles with sp3-carbon pronucleophiles, and shows potential applications in organic synthesis and medicinal chemistry.
The asymmetric transfer hydrogenation (ATH) reaction of prochiral ketones is an important method to produce chiral alcohols. Recently, the application of chiral amino acids and their derivatives as ligands in ATH of prochiral ketones promoted by the ruthenium, rhodium or iridium complexes have been attracted more attentions. Herein the catalytic properties of amino acids, amino acid based amides, thioamides, hydroxamic acids, hydrazides, amino alcohols and hydroxy amides as ligands in the ruthenium, rhodium or iridium catalyzed ATH of prochiral ketones have been overviewed. Keywords chiral amino acid; derivative of amino acid; metal complex of amino acid; asymmetric transfer hydrogenation
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