Synthesis of enantiomerically enriched 4-aryl-3,4-dihydrocoumarins (microreview)

Enantioselective synthesis of 4-aryl-3,4-dihydrocoumarins via N-heterocyclic carbene catalyzed β-arylation/cyclization of α-bromoenals

4-Aryl-3,4-dihydrocoumarins are one of the most important structural motifs. Herein, we disclose an enantioselective N-heterocyclic carbene catalyzed β-arylation/cyclization of α-bromoenals with 3-aminophenols under mild conditions. The protocol allows for the rapid preparation of 4-aryl-3,4-dihydrocoumarins in acceptable yields with good enantioselectivities. The products of this reaction could be converted into chiral diarylpropanoic acid derivatives without erosion of the enantioselectivity.

Palladium Catalyzed Enantioselective Hayashi-Miyaura Reaction for Pharmaceutically Important 4-Aryl-3,4-dihydrocoumarins

The first palladium-catalyzed asymmetric addition of arylboronic acids to coumarins was successfully established, providing a straightforward asymmetric approach to achieving pharmaceutically important 4-aryl-3,4-dihydrocoumarins. This methodology features easily accessible and bench-stable ligands, a wide substrate scope, mild conditions, and accommodation of electron-withdrawing arylboronic acids.

Organocatalytic Asymmetric Addition of Aromatic α-Cyanoketones to o-Quinone Methides: Synthesis of 3,4-Dihydrocoumarins and Tetrasubstituted Chromans

The first organocatalytic asymmetric addition of aromatic α-cyanoketones to in situ-generated o-quinone methides has been developed. The products 3,4-dihydrocoumarin and tetrasubstituted chroman were obtained via addition of aromatic α-cyanoketones to in situ-generated o-quinone methides followed by treatment with 0.7 N HCl. With 10 mol % catalyst, the desired products were obtained in high enantio- and diastereoselectivities.