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.