Dual Role of the Rhodium(III) Catalyst in C–H Activation: [4 + 3] Annulation of Amide with Allylic Alcohols to 7-Membered Lactams

Abstract

[4 + 3] annulation of primary and secondary benzamide and cinnamamide derivatives using allyl alcohol as a coupling partner catalyzed by Rh­(III) is reported, where Rh­(III) is playing a dual role of an oxidant and a catalyst for C–H activation. The Rh-catalyst oxidizes allyl alcohol to its carbonyl derivative, and the in situ-generated carbonyl compound reacts with benzamide in the presence of the Rh-catalyst, forming the corresponding alkylated products. Mechanistic studies show that AgSbF6 is also playing a dual role. Apart from being a halide scavenger, AgSbF6 catalyzes the cyclization of the alkylated product, forming the desired lactam. The current method has good synthetic application and is useful for synthesizing a few biologically active compounds that can act as the dopamine D3 receptor ligand, including berberine-like analogues. The deuteration study and control experiments helped us to propose the mechanism.

Mild Synthesis of 3,4-Dihydroisoquinolin-1(2H)-ones via Rh(III)-Catalyzed Tandem C–H-Allylation/N-Alkylation Annulation with 2-Methylidenetrimethylene Carbonate

“…Based on the mechanistic studies and previous literature, − we proposed a plausible catalytic cycle in Scheme . The active catalyst Cp*Rh­(III) species I generated from (Cp*RhCl 2 ) 2 , AgSbF 6 , and additive by a ligand exchange reacts with substrate 1 to produce the cyclometalated rhodium complex II via C–H activation.…”

“…Due to its high efficiency, less waste generation, and practical convenience, the process of a tandem catalytic reaction provides an ideal approach for the preparation of fine chemicals . In the past decade, the Cp*Rh­(III) catalyst has been successfully applied in allylation tandem reactions . Allylarene alcohols, which contain both electrophilic allyl alcohol moieties and nucleophilic amides, have recently become popular in tandem catalytic reactions .…”

Metal/Metal Dual Catalysis in C−H Activation

“…The construction of 7-membered lactams was achieved by a [4 + 3] annulation reaction catalyzed by Rh(III), [25] in which Rh(III) was playing a dual role both as an oxidant and a catalyst for CÀ H activation (Scheme 17). The allyl alcohol coupling partner 38 was firstly converted to corresponding α,β-unsaturated carbonyl compound under Rh-catalyst via β-hydride elimination.…”

Metal‐Catalyzed Approaches for the Construction of Azepinones

“…An anion exchange reaction with the rhodium and silver salt produces the active [Cp*Rh-(OAc) 2 ] 2 complex, which subsequently yields the cyclic rhodium ). [48] The optimal conditions for this reaction were Very recently, Ashfeld's group developed a methodology for the preparation of azepinone derivatives 122 from vinyl ketenes 125 and N-sulfonyl-1,2,3-triazoles 120 (Scheme 32). [49] Various 1,4-dipolar surrogates are available for this intermolecular rhodium mediated (4 + 3)-cycloaddition, howbeit vinyl ketenes enriched favorable yield.…”

“…al (Scheme 30). [48] The optimal conditions for this reaction were 2.5 mol% of [RhCp*Cl 2 ] 2 , 20 mol% of AgSbF 6 in HFIP at 60 °C with 2.0 equiv. of Cu(OAc) 2 H 2 O as an oxidant and Ad‐COOH as an additive (1.7 equiv.)…”