A Pd-Catalyzed Heteroannulation Approach to 2,3-Disubstituted Furo[3,2-c]coumarins

Abstract

The Pd-catalyzed cyclofunctionalization of 3-alkynyl-4-methoxycoumarins with aryl halides resulted in the selective formation of 3-arylfuro[3,2-c]coumarins in lieu of the expected regioisomeric 3-arylfuro[2,3-b]chromones. A mechanism involving the linear to angular rearrangement of a Pd-containing furan intermediate was proposed.

Palladium‐catalyzed cross‐coupling reactions of coumarin derivatives: An overview

“…Raffa et al put forward a novel idea of Pd‐catalyzed cyclofunctionalization of 3‐alkynyl‐4‐methoxycoumarins with aryl halides resulting in the selective formation of 3‐arylfuro[3,2‐ c ]coumarins in lieu of the expected regioisomeric 3‐arylfuro[2,3‐ b ]chromones (Scheme 25). [ 73 ] The model substrates used in the reaction are 4‐methoxycoumarin and ( p ‐MeO 2 C)‐phenyl iodide. Pd(PPh 3 ) 4 was found to be a particularly effective catalyst for this transformation when used in DMF at 100°C.…”

Metal-Catalyzed Routes for the Synthesis of Furocoumarins and Coumestans

“…Performing the same reaction at room temperature, or using K 2 CO 3 instead of Et 3 N as the base, the 3-alkynyl-4-methoxycoumarin 12 could be isolated in pure form [61,62]. In addition, starting from 12 and activated aryl iodides, a palladium-catalyzed electrophilic heteroannulation approach to 2,3-disubstituted furo[3,2-c]coumarins 14 was developed (Scheme 5) [62].…”

One‐pot Three‐component Synthesis of Furan‐based Heterocycles from Benzyl Halides

“…In recent years, few synthetic procedures for synthesis of furans have been well documented in the literature . Some of the protocols have been developed for the synthesis of furan with the use of various catalysts such as I 2 , Pd 0 , and many more . Although several synthetic methodologies have been reported, these methods suffer from 1 or more disadvantages such as the use of costly and less easily available reagents, harsh reaction conditions, and low yields.…”