Enaminone-directed ruthenium(II)-catalyzed C-H activation and annulation of arenes with diazonaphthoquinones for polycyclic benzocoumarins

Rhodium(III)-Catalyzed Sequential Cyclization of Enaminones with 1,3-Dienes via C-H Activation for the Synthesis of Fluorenones

An efficient method for construction of various fluorenones has been achieved via Rh(III)-catalyzed C-H activation/[4 + 2] annulation/aromatization sequences of simple and readily available enaminones and 1,3-dienes. This protocol showed good substrate compatibility as an array of structurally and electronically diverse fluorenones prepared efficiently in moderate to good yields and preparative scale utility showing very good efficiency in the late-stage functionalization of complex valuable molecules.

Recent advances in site-selective transformations of β-enaminones via transition-metal-catalyzed C-H functionalization/annulation

β-Enaminone transformation strategies are widely employed in the synthesis of numerous biologically active drugs and natural products, highlighting their significance in medicinal chemistry. In recent years, various strategies have been developed for synthesizing several five- and six-membered heterocycles, as well as substituted polyaromatic scaffolds, which serve as crucial synthons in drug development, from β-enaminones. Among these approaches, site-selective transformations of β-enaminones via C-H activation and annulation have been particularly well explored. This review summarizes the most recent literature (over the past eight years) on β-enaminone transformations for developing bioactive scaffolds through site-selective C-H bond functionalization and annulation.

Synthesis of Indenone-Fused Pyran Derivatives from Aryl Enaminones and Cyclopropenones through Unsymmetrical Relay C-H Bond Activation and Double C-C/C-O Bond Formation

Presented herein is a novel synthesis of indenone-fused pyran derivatives via the cascade reactions of aryl enaminones with cyclopropenones. The formation of products involves a one-pot cascade procedure consisting of aryl C-H bond and enamine C-H bond functionalization along with C-C bond cleavage of cyclopropenone and 1,3-rearrangement of the in situ-formed allylic alcohol moiety followed by intramolecular O-nucleophilic addition and Me2NH elimination. To our knowledge, this is the first synthesis of indenone-fused pyran derivatives via simultaneous formation of both indenone and pyran scaffolds through concurrent unsymmetrical relay C-H bond activation and double C-C/C-O bond formation. Moreover, the usefulness of this method is further showcased by its suitability for large-scale synthetic scenarios and diverse transformations of products.

Direct Aromatic Nitrosation Using 2-Methoxyethyl Nitrite as a NO Cation Source

This work presents an acid-free method for aromatic nitrosation using 2-methoxyethyl nitrite (MOE-ONO). While originally developed as a NOx radical source in our group, we demonstrate the utility of MOE-ONO as a NO cation source for aromatic electrophilic nitrosation. This method successfully nitrosates phenols, naphthols, and other pronucleophiles, completely suppressing undesired nitration by NOx radicals. Notably, it enables nitrosation of acid-sensitive substrates, which has been difficult to achieve with existing protocols.

Rh(II)-catalysed N2-selective arylation of benzotriazoles and indazoles using quinoid carbenes via 1,5-H shift

An efficient Rh(II)-catalyzed highly selective N2-arylation of benzotriazole, indazole, and 1,2,3 triazole is developed using diazonaphthoquinone. The developed protocol is extended with a wide scope. In addition, late-stage arylation of these scaffolds tethered with bioactive molecules is explored. Control experiments and DFT calculations reveal that the reaction proceeds presumably via nucleophilic addition of the N2 (of the 1H tautomer) center to quinoid-carbene followed by a 1,5-H shift.

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

Presented herein is an unprecedented 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. This protocol forms C-C and C-O bonds in one pot in which diazonaphthalen-2(1H)-ones serve as bifunctional reagents, providing both alkyl and aryloxy sources. To the best of our knowledge, this is the first example of an Ir(III)-catalyzed synthesis of the title compounds by using diazonaphthalen-2(1H)-ones as bifunctional substrates. Notably, this method features operational simplicity, good functional group tolerance, high efficiency, and high atom economy.