Silver‐Promoted Cascade Reaction of 4‐Hydroxycoumarins with α‐Keto Acids under Microwave Irradiation: One‐Step Construction of Quaternary Stereocenters

Abstract

A new Ag2O‐promoted cascade reaction of 4‐hydroxycoumarins with α‐keto acids under mircowave irradiation has been developed. The reaction provides an efficient approach to fused chromenes with quaternary stereocenters in 10 min, and gives good yields. Chromene derivatives can be prepared on a gram scale using this method.

Microwave-assisted decarboxylative reactions: advanced strategies for sustainable organic synthesis

“…The modular assembly of complex molecular backbones remains one of the most challenging topics in organic chemistry, so the development of new, selective, and efficient strategies is always in demand. [84][85][86] C-H activation has emerged as one of the most attractive and economical methods for the direct conversion of the substrate into a more complex molecule without any pre-functionalization. The carboxylic group, as a native directing group, can activate both C(sp 3 )-H and C(sp 2 )-H bonds at proximal as well as distal positions of aliphatic and aromatic compounds.…”

α-Keto Acids: Acylating Agents in Organic Synthesis

“…In 2016, Zha, Li, and Wang developed a new protocol to prepare fused chromenes 192 bearing a quaternary stereocenter through a microwave-assisted Ag­(I)-catalyzed cascade reaction between α-keto acids 1 and 4-hydroxycoumarins 191 . The protocol involves the irradiation with microwaves (110 °C) of an equimolar mixture of the α-keto acid 1 and 4-hydroxycoumarin 191 in the presence of Ag 2 O (10 mol %) and MeCN as solvent for 10 min.…”

“…In 2016, Zha, Li, and Wang 300 developed a new protocol to prepare fused chromenes 192 bearing a quaternary stereocenter through a microwave-assisted Ag(I)-catalyzed cascade reaction between α-keto acids 1 and 4-hydroxycoumarins 191.…”