Palladium-Catalyzed Oxidative Cross-Coupling of Conjugated Enynones with Allylarenes: Synthesis of Furyl-Substituted 1,3-Dienes

Abstract

A new method for the synthesis of furyl-substituted 1,3-dienes via palladium-catalyzed oxidative cross-coupling of conjugated enynones with allylarenes is developed. This reaction shows broad substrate scope and good functional group tolerance. Palladium carbene migratory insertion is proposed as the key step for this transformation with conjugated enynones serving as the carbene precursors.

Rh(III)-Catalyzed C–H Activation/Cycloisomerization of N-Phenoxyacetamides with Enynones for One-Pot Assembly of Furylated 2-Alkenylphenols

“…On the basis of our efforts, we herein disclose the first Rh­(III)-catalyzed redox-neutral C–H functionalization of N -phenoxyacetamides with enynones for one-pot assembly of furylated 2-alkenylphenols by using Cp* Cy as the Rh­(III) ligand (Scheme d), which represented a straightforward and step-economic route for direct assembly of complex furylated phenols from simple and readily accessible raw materials. Of note is that the α-methylene group of enynone moiety was found to be involved in this transformation as the H source for subsequent β H elimination, which was different from previous reports, − thus expanding the enynone-based synthetic chemistry. Moreover, the resulting products could serve as useful platforms for further synthetic transformations, such as for the synthesis of benzofuran/benzo­[ b ]­oxepine-fused and spirocyclic heterocycles.…”

“…In this regard, we realized that recently popular conjugated enynones should be able to conquer these limitations since they have emerged as one of the most valuable starting materials being widely applied in many important TM-catalyzed transformations by acting as the carbene precursors . Indeed, such a conjugated enynone-involved strategy has provided a more efficient method for the synthesis of furan derivatives via TM-catalyzed activation of the alkyne triple bond or the intramolecular nucleophilic attack of the carbonyl oxygen/5- exo -dig cyclization cascade (Scheme b) . Especially, more recently, Chang et al revealed the first example of the use of conjugated enynones as the carbene precursors via Rh­(III)-catalyzed carbenoid C–H insertion (Scheme c) .…”

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

“…Palladium‐catalyzed oxidative cross‐coupling reactions involving furylated carbene migratory insertion, reported by the same group, effectively produce 1,3‐diene‐substituted furans 49 from enynones 1 and allylarenes 48 (Scheme 19). [28] The proposed reaction mechanism begins with the formation of active Pd(II) species I , generated by ligand exchange between Pd(OAc) 2 and phosphoric acid. This species I activates the allylic C−H bond of allylarene 48 , leading to the formation of Pd‐π‐allyl complex II , accompanied by the removal of HX.…”

Silver(I)-Catalyzed Domino Cyclization/Cyclopropanation/Ring-Cleavage/Nucleophilic Substitution Reaction of Enynones with Enamines: Synthesis of 4-(Furan-2-yl)-3,4-dihydro-2H-pyrrol-2-one

“…Following the general procedure, the reaction was conducted of AgBF 4 (0.02 mmol, 5 mg), 3-(3-(4fluorophenyl)prop-2-yn-1-ylidene)pentane-2,4-dione 1d (0.2 mmol, 46 mg), and ethyl 3-amino-3-phenyl acrylate 2a (0.8 mmol, 154 mg) in DCM (3 mL) for 1 h. Yellow oil (45 mg, 59%), R f = 0.46 (PE:EA = 3:1). 1 H NMR (500 MHz, CDCl 3 , ppm) δ 8.04 (d,J = 6.5 Hz,2H),1H),2H),2H), 7.09− 7.06 (m, 2H), 6.45 (s, 1H), 3.59 (d, J = 18.5 Hz, 1H), 3.07 (d, J = 18.5 Hz, 1H), 2.56 (s, 3H), 2.35 (s, 3H). 13 C{1H} NMR (126 MHz,CDCl 3 ) δ195.4,193.5,191.8,162.1 (d,J = 247.5 Hz),158.9,150.7,137.2,134.3,132.1, 130.9, 128.8 (d, J = 7.5 Hz), 128.…”