Rh(III)-catalyzed oxidative [4+2] annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols

Synthesis of functionalized benzo[a]phenazines and indazolo[2,3-a]quinolines has been developed through Rh(III)-catalyzed oxidative annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols, respectively. The method features a broad substrate scope, excellent functional group tolerance, good to high yields of annulated products, and scaled-up synthesis capability. Based on a preliminary mechanistic investigation, a tentative mechanism of annulation reaction has been proposed.

Rhodium(i)-catalyzed cascade C(sp2)-H bond alkylation - amidation of anilines: phosphorus as traceless directing group

We introduce a versatile Rh(i)-catalyzed cascade reaction, combining C(sp2)-H bond functionalization and amidation between N-arylphosphanamines and acrylates. This innovative approach enables the rapid synthesis of dihydroquinolinone scaffolds, a common heterocycle found in various pharmaceuticals. Notably, the presence of the phosphorus atom facilitates the aniline ortho-C(sp2)-H bond activation prior to N-P bond hydrolysis, streamlining one-pot intramolecular amidation. Moreover, we demonstrate the applicability of this reaction by synthesizing an antipsychotic drug. Detailed mechanistic investigations revealed the involvement of a Rh-H intermediate, with substrate inhibition through catalyst saturation.

Palladium-Catalyzed C-H Allylation/Annulation Reaction of Amides and Allylic Alcohols: Regioselective Construction of Vinyl-Substituted 3,4-Dihydroisoquinolones

A palladium-catalyzed highly regioselective C-H allylation/annulation reaction of N-sulfonyl amides with secondary or tertiary allylic alcohols has been developed to construct 3,4-dihydroisoquinolones bearing a synthetically valuable vinyl substituent. This cascade cyclization approach of allylic alcohols involving C-H allylation has not been reported previously. The commercially available allylic alcohol substrates, the only by-product of water, and the used terminal oxidant of O₂ provide environmentally benign advantages.

Rhodium-Catalyzed β-Acylalkylation of Allylbenzene Derivatives with Allyl Alcohols via C-C Bond Cleavage

We report here a deallylative β-acylalkylation reaction of allylbenzene derivatives with allyl alcohols in the presence of Cp*Rh catalysts. Allylbenzenes possessing pyridyl and pyrazolyl directing groups were converted to β-aryl ketones via the cleavage of C(aryl)-C(allyl) bonds. Synthesis of a quinoline derivative from a β-aryl ketone product bearing a pyrazolyl group was also achieved.

Rhodium(III)-catalyzed oxidative annulation of isoquinolones with allyl alcohols: synthesis of isoindolo[2,1-b]isoquinolin-5(7H)-ones

An efficient rhodium(III)-catalyzed direct C-H oxidative annulation of isoquinolones with allyl alcohols as C1 synthons has been successfully developed. This protocol enables the straightforward synthesis of structurally diverse isoindolo[2,1-b]isoquinolin-5(7H)-ones with high atom economy, tolerates a broad spectrum of functionalities, and is applicable to one-pot operation from readily available N-methoxybenzamides.

Acyl silane directed Cp*Rh(III)-catalysed alkylation/annulation reactions

Studies into the Cp*Rh(iii)-catalysed hydroarylation of alkenes with aryl acyl silanes led to the discovery of a new synthetic strategy to access unique silicon derived indene frameworks. Rather than protodemetalation of the metal enolate formed following insertion of an alkene into the aryl C-H bond, intramolecular aldol condensation of the acyl silane occurred to generate a series of 2-formyl- and 2-acetyl-3-silyl indenes. This represents only the second example of rhodium-catalysed C-H functionalisation employing acyl silanes as weakly coordinating directing groups and the intramolecular aldol condensation strategy was extended to access analogous silicon derived benzofurans.

Rh(iii)-Catalyzed regioselective C4 alkylation of indoles with allylic alcohols: direct access to β-indolyl ketones

A Rh(iii)-catalyzed direct C4 alkylation of indoles with allylic alcohols to access β-indolyl ketones was developed.

A Rh(iii)-catalyzed redox-neutral C–H alkylation reaction with allylic alcohols by using a traceless oxidizing directing group

A Rh(iii)-catalyzed C–H alkylation of N-phenoxyacetamides with allylic alcohols has been developed to provide valuable β-aryl ketones under mild and redox-neutral conditions by using a traceless oxidizing directing group.

Cp*Rh(iii)-catalyzed C(sp3)–H alkylation of 8-methylquinolines in aqueous media

A mild and efficient approach for the cross-coupling reaction of 8-methylquinolines with a range of allylic alcohols in water as a solvent under rhodium(iii) catalysis is described.

Regioselectivity in C-H activation: reagent control in cyclometallation of 2-(1-naphthyl)-pyridine

2-(1-Naphthyl)-pyridine () possesses sp(2) C-H bonds in both the γ- and δ-positions and is therefore a suitable substrate for studying the cyclometallation selectivity with different reagents and conditions. Such selectivity studies are reported. Based on deuterium-exchange experiments it is concluded that cycloruthenation with RuCl2(p-cymene) dimer is reversible with kinetic and thermodynamic preference for γ-substitution. Electrophilic cycloborylation, on the other hand, shows unusual δ-substitution. The previously published cyclopalladation and cycloauration of the substrate was studied in detail and was shown to be irreversible; they proceed under kinetic control and give γ- and δ-substitution for palladium and gold, respectively.

Cobalt-catalyzed C–H olefination of aromatics with unactivated alkenes

A cobalt-catalyzed C–H olefination of aromatic and heteroaromatic amides with unactivated alkenes, allyl acetates and allyl alcohols is described. This method offers an efficient route for the synthesis of vinyl and allyl benzamides in a highly stereoselective manner.

Ru-catalysed C-H arylation of indoles and pyrroles with boronic acids: scope and mechanistic studies

The Ru-catalysed C2–H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole-based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on-cycle intermediates do not possess a para-cymene ligand and that the on-cycle metalation occurs through an electrophilic attack by the Ru centre.

Synthesis of isoindolinones via a ruthenium-catalyzed cyclization of N-substituted benzamides with allylic alcohols

A ruthenium-catalyzed cyclization of N-substituted benzamides with allylic alcohols affording 3-substituted isoindolinone derivatives in good to excellent yields is described.

Metal controlled regioselectivity in the cyclometallation of 2-(1-naphthyl)-pyridine

Cyclometallations of 2-(1-naphthyl)-pyridine with gold and palladium salts proceed with completely orthogonal regioselectivities.