Ag(I)-Catalyzed Tandem Reaction of Conjugated Ene-yne-ketones in the Presence of PhI(OAc)₂ and Triethylamine: Synthesis of 2-Alkenylfurans

Abstract

Silver-catalyzed tandem cyclization–elimination reactions of conjugated ene-yne-ketones in PhI­(OAc)2/triethylamine system lead to the formation of 2-alkenylfurans. 2-Furylsilver carbene and phenyliodonium ylide are proposed as the key intermediates in these transformations.

Silver(I)-Catalyzed Tandem Reaction of Enynones and 4-Alkenyl Isoxazoles: Synthesis of 2-(Furan-2-yl)-1,2-dihydropyridines

“…According to our results and the mechanistic studies reported in literatures, a plausible catalytic cycle for the formation of the desired product 3 is proposed in Scheme . Silver­(I)-catalyzed tandem cyclization of enynone 1 gave (2-furyl)­silver carbene intermediate A . The selective N–O bond insertion of 4-alkenyl isoxazole 2 by the carbene intermediate A forms an intermediate B , and silver­(I) catalyst was recycled.…”

Accessing Functionalized Furans from Reacting Enynones and Enynals through Furyl Metal Carbenes

“…In 2019, the Deng group reported an Ag(I)catalyzed cross-coupling reaction using enynones 1 and PhI(OAc) 2 , leading to the formation of 2-alkenylfurans 64 with moderate yields (Scheme 24A). [34] This process begins with the formation of furyl silver carbene I through AgOAc-catalyzed intramolecular 5-exo-dig cyclization of enynone 1. The carbene I then undergoes cross-coupling with PhI(OAc) 2 63, generating phenyl iodonium ylide and AgOAc catalyst.…”

“…Recently, synthetic methods for synthesizing 2‐alkenylfurans have been revealed, involving Ag(I)‐catalyzed furyl metal carbene formation/cross‐coupling reactions with iodonium or phosphorous ylides, followed by an elimination cascade (Scheme 24). In 2019, the Deng group reported an Ag(I)‐catalyzed cross‐coupling reaction using enynones 1 and PhI(OAc) 2 , leading to the formation of 2‐alkenylfurans 64 with moderate yields (Scheme 24A) [34] . This process begins with the formation of furyl silver carbene I through AgOAc‐catalyzed intramolecular 5‐exo‐dig cyclization of enynone 1 .…”

A ligand-enabled, copper(ii)-catalyzed, highly selective and efficient synthesis of 2E-alkenylfurans from ynenones

“…Ynenones have been reported for the synthesis of furan derivatives 4 in the presence of transition-metal catalysts such as gold, palladium, silver, rhodium, and copper. 5–10 Most of the reported reactions have been proposed to proceed after carbene insertion or dimerization of α-furyl metal carbene intermediates, during which an air-free environment is required (Scheme 1A). Moreover, the in situ -generated α-furyl carbene complexes A from ynenones can be oxidized readily to 2-acyl furan 9 b ,10 c in an air atmosphere, and even an alkyl group can be installed at the end of an alkyne (Scheme 1A).…”