Organocatalytic Reductive Propargylation: Scope and Applications

An amino acid-catalyzed three-component reductive coupling protocol has been developed for the selective high-yielding synthesis of nearly fifty examples of propargylated cyclic/acyclic systems from the various propargyl aldehydes, cyclic/acyclic CH acids, and Hantzsch ester under ambient conditions. It is an economical, efficient, catalytic, metal-free protocol for the quick gram-scale synthesis of propargylated cyclic/acyclic compounds, and many of these coupling compounds were purified by a simple precipitation-filtration technique instead of column chromatography. Functionally rich propargylated cyclic-1,3-diketones were specifically transformed into dihydropyrans found in natural products and drugs through an annulative etherification reaction by using Lewis-acid (AgOTf) catalysis. Further, we developed the C-methylation reactions on propargylated cyclic-1,3-diketones, which are prolific synthons in natural products and medicinal chemistry.