Switching the Reactivity of the Nickel-Catalyzed Reaction of 2-Pyridones with Alkynes: Easy Access to Polyaryl/Polyalkyl Quinolinones

Abstract

A Ni-catalyzed C6 followed by C5 cascade C−H activation/[2 + 2 + 2] annulation of 2-pyridone with alkynes has been achieved. A change in the reaction pathway was achieved by tuning the reaction conditions and incorporating a directing group. A wide variety of substrates and alkynes are amenable to this transformation. The key to success for this transformation is the use of sodium iodide as an additive. More importantly, we detected the five-membered metallacycle intermediate through HRMS wherein iodide is ligated to the metal.

Directing group-assisted selective C–H activation of six-membered N-heterocycles and benzo-fused N-heterocycles

“…89 Recently, the Ravikumar group reported the synthesis of quinolinones by using Ni catalyst (Scheme 55). 90 Optimization was initiated by taking N-pyridyl pyridones 74 as the substrate and diphenylacetylene 12 as the coupling partner. After variation of several parameters, Ni (acac) 2 (10 mol%) as the catalyst, PPh 3 (20 mol%) as the ligand, NaI (50 mol%) as the additive in CH 3 CN (0.2 M) at 160 °C for 24 h was found to be the optimised reaction condition.…”

Nickel-Catalyzed Tandem Cyclization of 1,6-Diynes with Indolines/Indoles through Dual C–H Bond Activation

“…In this regard, a significant advance has been done with the nickel catalyst for the arene C–H bond functionalization. − However, in most of the reported nickel-catalyzed C–H bond functionalization reactions, directing groups having two chelating centers are required to stabilize the metal center effectively . In fact, the development of nickel-catalyzed dual C–H bond functionalization reaction by using a monodentate directing group is underdeveloped . The indoline and indole scaffolds are common structural motifs that are involved in a wide variety of natural alkaloids, medicines, agrochemicals, and organic compounds .…”

“…It will be highly desirable and attractive to use cost-effective and earth-abundant first-row transition metal complexes as catalysts for achieving these reactions. In this regard, a significant advance has been done with the nickel catalyst for the arene C–H bond functionalization. − However, in most of the reported nickel-catalyzed C–H bond functionalization reactions, directing groups having two chelating centers are required to stabilize the metal center effectively . In fact, the development of nickel-catalyzed dual C–H bond functionalization reaction by using a monodentate directing group is underdeveloped .…”

Synthesis of Naphtho[1′,2′:4,5]furo[3,2-b]pyridinones via Ir(III)-Catalyzed C6/C5 Dual C–H Functionalization of N-Pyridyl-2-pyridones with Diazonaphthalen-2(1H)-ones

“…As an important and readily available synthetic building block, 2-pyridone has four possible reactive C–H bonds on the pyridone ring (C3–C6). Therefore, it is frequently used in TM-catalyzed C–H bond functionalization reactions, − mainly including alkylation, alkenylation, alkynylation, arylation, and borylation. To date, most studies of 2-pyridones have focused on monofunctionalization at different sites on the pyridone ring, while there have been relatively few examples of the bifunctionalization on pyridone to construct fused heterocycles.…”

“…On the basis of the mechanistic studies mentioned above and literature precedent, ,− a plausible mechanism for the formation of 3aa was proposed as shown in Scheme . Initially, [Cp*IrCl 2 ] underwent ligand exchange with a Ag salt to generate an active catalyst [Cp*IrX 2 ].…”