Palladium-Catalyzed Synthesis of 4-Arylcoumarins Using Triarylbismuth Compounds as Atom-Efficient Multicoupling Organometallic Nucleophiles

Pd-Catalyzed cross-coupling synthesis of 4-aryl-3-formylcoumarins

The threefold cross-coupling of triarylbismuth reagents with 4-chloro-3-formylcoumarins furnished the corresponding 4-aryl-3-formylcoumarins in a chemoselective manner with high yields under Pd-catalyzed conditions. This method was successfully applied to electronically different triarylbismuth reagents and 4-chloro-3-formylcoumarins preserving the 3-formyl group in the coumarin scaffold.

Recent Advances in Synthesis of 4-Arylcoumarins

4-Arylcoumarins (4-aryl-2H-1-benzopyran-2-one), also known as neoflavones, comprise a minor subclass of naturally occurring flavonoids. Because of their broad-spectrum biological activities, arylcoumarins have been attracting the attention of the organic and medicinal chemistry communities, and are considered as an important privileged scaffold. Since the development of Pechmann condensation, a classical acid-catalyzed condensation between phenol and β-keto-carboxylic acid, several versatile and efficient synthetic approaches for 4-arylcoumarins have been reported. This review summarizes recent advances in the synthesis of the 4-arylcoumarin scaffold by classifying them based on the final bond-formation type. In particular, synthetic methods executed under mild and highly efficient conditions, such as solvent-free reactions and transition metal catalysis, are highlighted.

Cross-coupling reactivity of 1,1-dichloroalkenes under palladium catalysis: domino synthesis of diarylalkynes

An efficient synthesis of diarylalkynes was achieved from the domino cross-coupling reaction of 1,1-dichloroalkenes with triarylbismuth reagents under palladium-catalyzed conditions.

Palladium-catalyzed oxidative Heck coupling reaction for direct synthesis of 4-arylcoumarins using coumarins and arylboronic acids

An efficient protocol for the direct synthesis of 4-arylcoumarins via palladium-catalyzed oxidative Heck coupling reaction of coumarins and arylboronic acids was developed. 4-Arylcoumarins were obtained in moderate to excellent yields, and the reaction also showed tolerance toward functional groups such as hydro, methoxy, diethylamino, nitro, and chloro groups.