Rh(III)‐Catalyzed Divergent C2‐carboxymethylation of Indoles and C7‐formylmethylation of Indolines with Vinylene Carbonate

Synthesis of Fluoren-9-ones via Pd-Catalyzed Annulation of 2-Iodobiphenyls with Vinylene Carbonate

A palladium-catalyzed reaction for intermolecular selective C-H cyclocarbonylation of 2-iodobiphenyls is described. Intriguingly, the vinylene carbonate acts as a carbon monoxide transfer agent to enable the annulation reaction. Moreover, as a versatile synthon, fluoren-9-one can be transformed into a variety of functionalized organic molecules, such as [1,1'-biphenyl]-2-carboxylic acid, 1'H,3'H-spiro[fluorene-9,2'-perimidine] and N-tosylhydrazones.

Rhodium-catalyzed divergent dehydroxylation/alkenylation of hydroxyisoindolinones with vinylene carbonate

Herein, a novel organic transformation involving rhodium-catalyzed divergent dehydroxylation/alkenylation of hydroxyisoindolinone with vinylene carbonate is reported, and a series of architecturally rigid and widely used spirolactams are obtained with excellent functional group tolerance and high selectivity. Remarkably, the promising vinylene carbonate reagent presents a distinct chemical reactivity as a vinyl-oxygen cyclic synthon and first transfers the C-H bond to spiroheterocycle scaffolds. Moreover, another chemoselectivity, direct dehydrogenative coupling with vinylene carbonate, is also presented. This protocol is compatible with green chemistry and only releases H2O and CO2 as byproducts.

Base-Catalyzed Nucleophilic Addition Reaction of Indoles with Vinylene Carbonate: An Approach to Synthesize 4-Indolyl-1,3-dioxolanones

The N-functionalized indole is a privileged structural framework in a wide range of bioactive molecules. The nucleophilic addition between indoles with vinylene carbonate proceeded smoothly in the presence of K2CO3 as the catalyst to produce novel indolyl-containing skeletons and 4-indolyl-1,3-dioxolanones in satisfactory to excellent yields (up to >97% yield). Various synthetically useful functional groups, such as halogen atoms, cyano, nitro, and methoxycarbonyl groups, remained intact during the regioselective N-H addition reactions. The developed catalytic system also could accommodate 2-naphthalenol to achieve the target O-H additive product in good yield.

Rhodium-catalyzed C-H carboxymethylation of anilines with vinylene carbonate

A rhodium-catalyzed synthesis of phenylacetate has been realized by direct C-H carboxymethylation of anilines bearing removable directing groups. The reaction occurred most efficiently in air, without any external base or oxidant. This methodology is expected to provide a facile and general access to various bioactive 2-amino aromatic acetic acid derivatives.

Rhodium(III)-Catalyzed C-H/N-H Activation for Direct Synthesis of Pyrimidoindolones under Mild Conditions

Pyrimidoindolones are an important structural motif found in many natural products and are essential to the pharmaceutical and agrochemical industry. Direct synthesis of 3,4-unsubstituted pyrimidoindolones is not easily accessible. Here we report a rhodium(III)-catalyzed C-H/N-H activation and annulation approach for obtaining pyrimidoindolones from N-carbamoylindoles and vinylene carbonate. The reaction occurs at room temperature and does not require any external oxidants. A diverse spectrum of indoles were demonstrated to be viable substrates capable of producing the desired pyrimidoindolones in high yields. In addition, the reaction scope has been expanded to include pyrrole substrate. Furthermore, detailed mechanistic studies have been performed to delineate the working mode of the reaction.

Selective Synthesis of C4-Functionalized Benzofurans by Rhodium-Catalyzed Vinylene Transfer: Computational Study on the Cyclopentadienyl Ligand

Benzofuran is a privileged structure in many bioactive compounds; however, the controlled synthesis of C2,C3-nonsubstituted benzofurans has been scarce. In particular, cumbersome multistep processes are inevitable for the most inaccessible C4-substituted isomers. Herein, we report a Rh-catalyzed direct vinylene annulation of readily available m-salicylic acid derivatives with vinylene carbonate to achieve selective construction of C4-substituted benzofurans. The Weinreb amide directing group facilitated the following product derivatization. The reaction mechanism was investigated by DFT calculations.

Rhodium-Catalyzed C-H Annulation of Free Anilines with Vinylene Carbonate as a Bifunctional Synthon

Chemical transformation with vinylene carbonate as an emerging synthetic unit has recently attracted considerable attention. This report is a novel conversion pattern with vinylene carbonate, in which such a vibrant reagent unprecedentedly acts as a difunctional coupling partner to complete the C-H annulation of free anilines. From commercially available substrates, this protocol leads to the rapid construction of synthetically versatile 2-methylquinoline derivatives (43 examples) with excellent functionality tolerance.