Rh(III)-Catalyzed Weakly Coordinating 2-Pyridone-Directed Oxidative Annulation Using Internal Alkynes: A Reversal in Selectivity

Abstract

A rhodium(III)-catalyzed Satoh−Miura type oxidative annulation of N-aryl 2-pyridone derivatives is described using internal alkyne as a coupling partner. A weakly coordinating carbonyl group of the 2-pyridone ring is utilized for this transformation. The reaction proceeds with a broad scope and wide functional group tolerance. The solvent plays an important role in the developed method to furnish a different class of annulated product. A preliminary investigation was carried out to explore the photophysical properties of the obtained polyarylated N-naphthyl 2-pyridones.A mong various known 2-pyridone-based moieties, the Naryl 2-pyridone scaffold is considered as an important structural scaffold due to its frequent presence in pharmaceuticals, drug molecules, and organic materials (Figure 1). 1

Pd(II)-Catalyzed Oxidative Naphthylation of 2-Pyridone through N–H/C–H Activation Using Diarylacetylene as an Uncommon Arylating Agent

“…To the best of our knowledge, there is no report where the chemoselective oxidative naphthylation occurred with a twofold internal alkyne via N–H/C–H activation. Intrigued by our previous efforts on 2-pyridone functionalizations, especially with internal alkynes, , we hypothesized that the transition-metal-catalyzed oxidative naphthylation of the unmasked 2-pyridone with twofold internal alkynes might directly provide the N -naphthyl 2-pyridone frameworks via N–H/C–-H activation. However, the major challenge in this type of 2-pyridone N–H activation strategy is the control of the initial N -metalation over the O -metalation of the ambident nucleophilic 2-pyridone moiety .…”

“…8 Very recently, we developed a weakly coordinating 2-pyridonedirected Rh(III)-catalyzed oxidative annulation of N-phenyl 2- pyridone to afford its N-naphthyl derivatives via twofold C−H activation of the phenyl ring (Scheme 1c). 9 In this method, the formed naphthyl ring contains a 2-pyridone-linked unsubstituted phenyl ring fused with an adjacent polyarylated phenyl ring. To develop a complementary approach in this perspective, we planned to build the naphthalene skeleton where the 2-pyridone-attached phenyl ring would be polyarylated and the fused other phenyl ring would be unsubstituted.…”

“…However, this mode of unusual oxidative naphthylation is scarce . Very recently, we developed a weakly coordinating 2-pyridone-directed Rh­(III)-catalyzed oxidative annulation of N -phenyl 2-pyridone to afford its N -naphthyl derivatives via twofold C–H activation of the phenyl ring (Scheme c) . In this method, the formed naphthyl ring contains a 2-pyridone-linked unsubstituted phenyl ring fused with an adjacent polyarylated phenyl ring.…”

Three-Component Chemo-Selective Synthesis of N-(o-Alkenylaryl) Pyrazoles by Pyrazole Annulation and Rh-Catalyzed Chemo-Selective Aryl C–H Addition Cascade

“…As typical examples of widespread C–H activation synthesis, the Rh-catalyzed reactions of N -aryl pyrazoles with alkynes have been disclosed to be capable of providing diverse products depending on the reaction conditions and substrate structures. − However, as reported by Miura and Satoh et al, when the N -phenyl pyrazoles and internal alkynes were employed to rhodium catalysis, the N -naphthyl pyrazoles resulting from the benzannulation of the two adjacent aryl C–H bonds with two alkyne molecules were the products (Scheme A). Over the last decade, a number of such benzannulation reactions have been developed with the assistance of different coordinating structures. − The most typical advances in the area are the nonchelate aryl C–H benzannulation developed by Cramer (Scheme B) and the asymmetric Satoh–Miura benzannulation reported by Wang, You, and Zheng groups (Scheme C), respectively. However, controlling the reaction selectivity to stop in the stage of direct aryl C–H alkenylation by the hydroarylation in the alkynes has not been hitherto realized.…”

Rh(II)-Catalyzed Synthesis of N-Aryl 2-pyridone Using 2-Oxypyridine and Diazonaphthoquinone Via 1,6-Benzoyl Migratory Rearrangement

“…Very recently, our group developed an N -arylation of the amide center using migratory insertion of quinoid carbene, generated from diazonaphthoquinone . Additionally, we also developed 2-pyridone N -naphthylation using an internal alkyne as a coupling partner . Strategically, 2-oxypyridines were explored as a starting platform to react with metal carbenes via N -metalation over O -metalation with diazo and other carbene precursors. , …”