Rh(III)-Catalyzed C–H Activation and Double Directing Group Strategy for the Regioselective Synthesis of Naphthyridinones

Synthesis of Organofluoro Compounds Using Methyl Perfluoroalk-2-ynoates as Building Blocks

This review provides an overview of several synthetic applications of methyl perfluoroalk-2-ynoates, leading to convenient preparation of many perfluoroalkylated compounds. The use of these important substrates in the synthesis of various five-, six-, and seven-membered heterocycles, cyclopentadienes, and biphenyls is described, alongside a discussion of the mechanistic aspects of these reactions.

Synthesis of isoquinolines via Rh-catalyzed C–H activation/C–N cyclization with diazodiesters or diazoketoesters as a C2 source

Synthesis of isoquinolines based on efficient C–C and C–N bond formation through Rh(iii)-catalyzed C–H functionalization and subsequent intramolecular cyclization is reported. Diazodiesters serving as a C₂ source in the newly formed heterocycles are first demonstrated.

Mechanism of the rhodium(iii)-catalyzed alkenylation reaction of N-phenoxyacetamide with styrene or N-tosylhydrazone: a computational study

A systematic density functional theory study has been conducted to examine the mechanisms involved in the rhodium(iii)-catalyzed alkenylation ofN-phenoxyacetamide with two different substrates (i.e., styrene andN-tosylhydrazone).

Divergent synthesis of indoles, oxindoles, isocoumarins and isoquinolinones by general Pd-catalyzed retro-aldol/α-arylation

Divergent synthesis of indoles, oxindoles, isocoumarins and isoquinolinones is achieved by a general Pd-catalyzed retro-aldol reaction of β-hydroxy ketones/esters with aryl halides bearing an ortho-nitro, -ester or -nitrile group. DFT insights have been presented to rationalize the experimental observations and the chemoselectivity.

The microwave-assisted ortho-alkylation of azine N-oxides with N-tosylhydrazones catalyzed by copper(i) iodide

A regioselective direct ortho-alkylation of azine N-oxides has been achieved under ligand-free conditions using copper(i) iodide and microwave conditions.

Surprisingly Facile C-H Activation in the Course of Oxime-Directed Catalytic Asymmetric Hydroboration

Deuterium-labeling studies carried out in conjunction with investigations into the directed catalytic asymmetric hydroboration of unsaturated oxime ethers reveal a surprisingly facile ortho-metallation or σ-bond metathesis pathway that that diverts the expected course of CAHB to a tandem C-H activation/hydroboration reaction pathway.

Rhodium-catalyzed C-H activation of phenacyl ammonium salts assisted by an oxidizing C-N bond: a combination of experimental and theoretical studies

Rh(III)-catalyzed C-H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite the success, these coupling systems are currently limited to cleavage of an oxidizing N-O or N-N bond. Cleavage of an oxidizing C-N bond, which allows for complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with an oxidizing C-N bond have been designed as substrates for Rh(III)-catalyzed C-H activation under redox-neutral conditions. The coupling with α-diazo esters afforded benzocyclopentanones, and the coupling with unactivated alkenes such as styrenes and aliphatic olefins gave ortho-olefinated acetophenoes. In both systems the reactions proceeded with a broad scope, high efficiency, and functional group tolerance. Moreover, efficient one-pot coupling of diazo esters has been realized starting from α-bromoacetophenones and triethylamine. The reaction mechanism for the coupling with diazo esters has been studied by a combination of experimental and theoretical methods. In particular, three distinct mechanistic pathways have been scrutinized by DFT studies, which revealed that the C-H activation occurs via a C-bound enolate-assisted concerted metalation-deprotonation mechanism and is rate-limiting. In subsequent C-C formation steps, the lowest energy pathway involves two rhodium carbene species as key intermediates.

Rhodium-catalyzed (5+1) annulations between 2-alkenylphenols and allenes: a practical entry to 2,2-disubstituted 2H-chromenes

Readily available alkenylphenols react with allenes under rhodium catalysis to provide valuable 2,2-disubstituted 2H-chromenes. The whole process, which involves the cleavage of one C-H bond of the alkenyl moiety and the participation of the allene as a one-carbon cycloaddition partner, can be considered a simple, versatile, and atom-economical (5+1) heteroannulation. The reaction tolerates a broad range of substituents both in the alkenylphenol and in the allene, and most probably proceeds through a mechanism involving a rhodium-catalyzed C-C coupling followed by two sequential pericyclic processes.

Regioselective synthesis of multisubstituted isoquinolones and pyridones via Rh(iii)-catalyzed annulation reactions

A mild and efficient Rh(iii)-catalyzed regioselective synthesis of isoquinolones and pyridones from N-methoxybenzamide or N-methoxymethacrylamide and diazo compounds has been developed, through tandem C–H activation, cyclization, and condensation.

One-pot cascade synthesis of N-methoxyisoquinolinediones via Rh(iii)-catalyzed carbenoid insertion C–H activation/cyclization

A mild and efficient method for one-pot synthesis of N-methoxyisoquinolinediones via Rh(iii)-catalyzed carbenoid insertion C–H activation/cyclization has been developed.

Transition metal-catalyzed C–H functionalization of N-oxyenamine internal oxidants

The N-oxyenamine internal oxidant gives more chance to investigate the C–H bond activation under mild reaction conditions.

Step economical synthesis of o-aryl benzamides via C–H activation relayed by the in situ installation of directing group: a multicomponent method

Multicomponent reactions have been successfully applied as a platform for the step economical C–H activation based synthesis wherein the in situ installation of directing group and the subsequent C–H arylation have been achieved in one-step.

Transition metal-catalyzed C–H bond functionalizations by the use of diverse directing groups

In this review, a summary of transition metal-catalyzed C–H activation by utilizing the functionalities as directing groups is presented.

Rhodium-catalyzed C–H activation of hydrazines leads to isoquinolones with tunable aggregation-induced emission properties

We report a Rh^III-catalyzed synthesis of isoquinolonesviaC–H activation/annulation of benzoylhydrazines and alkynes for AIE studies.

Theoretical studies of palladium-catalyzed cycloaddition of alkynyl aryl ethers and alkynes

Density functional theory (DFT) was used to investigate palladium(0)-catalyzed cycloaddition of alkynyl aryl ethers and alkynes to generate 2-methylidene-2H-chromenes. Calculations indicated that the cycloaddition had five possible reaction pathways: I, II, III, IV, and V. In the palladium(0)-alkynyl aryl ether complex IM1, the oxidative addition of the Caryl-H bond occurred prior to the dissociation of a ligand PMe3. The dissociation of a ligand PMe3 from the five-coordinated complex IM2 was much easier to achieve than the hydrogen transfer reaction and the substitution reaction of alkynes. In the palladium(0)-hydride complex IM4, the hydrogen migration of H1 from palladium to carbon C1 was much easier to achieve than migration to carbon C2. In the four-coordinated aryl-palladium-alkyne complexes IM6a and IM6b, the alkyne insertion reaction into the Pd-Caryl bond occurred prior to that into the Pd-Calkenyl bond. The reaction channel IM1 → TS1 → IM2 → IM4 → TS3a → IM5a → IM6a → TS4a1 → IM7a1 → TS5a1 → IM8a was the most favorable among the catalytic reaction pathways of the cycloaddition of alkynyl aryl ethers and 2-butynes catalyzed by the palladium(0)/PMe3 complex. Moreover, hydrogen migration was the rate-determining step for this channel. The dominant product was 2-methylidene-2H-chromenes P1, which is in agreement with experimental studies.

Rhodium(III)-catalyzed transannulation of cyclopropenes with N-phenoxyacetamides through C-H activation

An efficient rhodium(III)-catalyzed synthesis of 2H-chromene from N-phenoxyacetamides and cyclopropenes has been developed. The reaction represents the first example of using cyclopropenes as a three-carbon unit in rhodium(III)-catalyzed C(sp(2))-H activations.