One-Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)-Catalyzed Multiple CH Activation and Annulation

Cationic Cobalt(III) Catalyzed Indole Synthesis: The Regioselective Intermolecular Cyclization of N-Nitrosoanilines and Alkynes

The unique regioselectivity and reactivity of cobalt(III) in the direct cyclization of N-nitrosoanilines with alkynes for the expedient synthesis of N-substituted indoles is demonstrated. In the presence of a cobalt(III) catalyst, high regioselectivity was observed when using unsymmetrical meta-substituted N-nitrosoanilines. Moreover, internal alkynes bearing electron-deficient groups, which are almost unreactive in the [Cp*Rh(III)]-catalyzed system, display good reactivity in this transformation.

Copper-catalyzed 8-amido chelation-induced regioselective C–H fluoroalkylation of quinolines

An effective and regioselective approach for C–H fluoroalkylation of 8-aminoquinoline amides with R_fSO₂Na is demonstrated herein.

Visible-light-induced regioselective synthesis of polyheteroaromatic compounds

A method for visible-light-induced synthesis of heteroaryl-substituted polyheteroaromatics was developed.

A unique annulation of 7-azaindoles with alkenyl esters to produce π-conjugated 7-azaindole derivatives

Rhodium(iii)-catalyzed N-directed ortho C–H activation and subsequent roll-over C–H activation represents an important strategy to synthesize fused polycyclic compounds.

Rhodium(iii)-catalyzed ortho-alkenylation using a cyclic N-phosphoryl ketimine as the directing group

A novel cyclic N-phosphoryl ketimine structure can efficiently react with olefins as useful directing groups to construct a myriad of phosphate scaffolds via rhodium(iii)-catalyzed ortho-alkenylation.

A facile access to substituted cationic 12-azapyrene salts by rhodium(iii)-catalyzed C–H annulation of N-arylpyridinium salts

Rhodium(iii)-catalyzed C–H annulation of N-arylpyridinium salts with internal alkynes directly affords substituted cationic 12-azapyrene salts, which exhibit tunable and intense fluorescence.

Synthesis of substituted benzo[ij]imidazo[2,1,5-de]quinolizine by rhodium(iii)-catalyzed multiple C–H activation and annulations

The cascade oxidative annulation reactions of aryl imidazoles with two molecules of alkynes via multiple C–H activation proceed efficiently in the presence of [Cp*RhCl₂]₂ and Cu(OAc)₂·H₂O to give substituted benzo[ij]imidazo[2,1,5-de]quinolizine-based polyheteroaromatic compounds.

Direct Synthesis of Protoberberine Alkaloids by Rh-Catalyzed C-H Bond Activation as the Key Step

A one-pot reaction of substituted benzaldehydes with alkyne-amines by a Rh-catalyzed C-H activation and annulation to afford various natural and unnatural protoberberine alkaloids is reported. This reaction provides a convenient route for the generation of a compound library of protoberberine salts, which recently have attracted great attention because of their diverse biological activities. In addition, pyridinium salt derivatives can also be formed in good yields from α,β-unsaturated aldehydes and amino-alkynes. This reaction proceeds with excellent regioselectivity and good functional group compatibility under mild reaction conditions by using O2 as the oxidant.

RhI/RhIII catalyst-controlled divergent aryl/heteroaryl C-H bond functionalization of picolinamides with alkynes

The ability to establish switchable site-selectivity through catalyst control in the direct functionalization of molecules that contain distinct C-H bonds remains a demanding challenge that would enable the construction of diverse scaffolds from the same starting materials. Herein we describe the realization of this goal, namely a divergent heteroaryl/aryl C-H functionalization of aromatic picolinamide derivatives, targeting two distinct C-H sites, either at the pyridine ring or at the arene unit, to afford isoquinoline or ortho-olefinated benzylamine (or phenethylamine) derivatives. This complementary reactivity has been achieved on the basis of a RhIII/RhI switch in the catalyst, resulting in different mechanistic outcomes. Notably, a series of experimental and DFT mechanistic studies revealed important insights about the mechanism of the reaction and reasons behind the divergent regiochemical outcome.

All-Carbon [3+3] Oxidative Annulations of 1,3-Enynes by Rhodium(III)-Catalyzed C-H Functionalization and 1,4-Migration

1,3-Enynes containing allylic hydrogens cis to the alkyne function as three-carbon components in rhodium(III)-catalyzed, all-carbon [3+3] oxidative annulations to produce spirodialins. The proposed mechanism of these reactions involves the alkenyl-to-allyl 1,4-rhodium(III) migration.

Rh(III)-catalyzed oxidative annulation of 2-phenylimidazo[1,2-a]pyridines with alkynes: mono versus double C-H activation

Rh(III)-catalyzed C-H activation of 2-phenylimidazo[1,2-a]pyridines in divergent oxidative coupling with alkynes has been achieved. Selective mono versus 2-fold C-H activation has been attained under condition control. When AgOAc was used as an oxidant, the coupling afforded 5,6-disubstituted naphtho[1',2':4,5]imidazo[1,2-a]pyridines as a result of initial nitrogen chelation-assisted C-H activation at the benzene ring followed by rollover C-H activation. In contrast, the reaction afforded a fused isoquinolinium salt as a result of C-C and C-N coupling when AgBF4 was employed as a co-oxidant. A rhodacyclic intermediate has been isolated.

Synthesis of spiroindanes by palladium-catalyzed oxidative annulation of non- or weakly activated 1,3-dienes involving C–H functionalization

The palladium-catalyzed oxidative annulation of non- or weakly activated 1,3-dienes with 2-aryl cyclic 1,3-dicarbonyl compounds is described.

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.

Rh-catalysed direct cyclisation of 1,4-naphthoquinone and 9,10-phenanthraquinone with alkyne: facile access to 1,8-dioxapyrenes and 1,12-dioxaperylenes as orange and red-emitting luminophores

Rh-catalysed direct cyclisation of quinones with alkynes has been accomplished through C–H activation strategy.

Rhodium(iii)-catalyzed C–H activation and intermolecular annulation with terminal alkynes: from indoles to carbazoles

A new and mild Rh(iii)-catalyzed intermolecular annulation of indoles with terminal alkynes for the direct synthesis of carbazoles has been developed.

Palladium-Catalyzed Cascade Reaction of 2-Amino-N'-arylbenzohydrazides with Triethyl Orthobenzoates To Construct Indazolo[3,2-b]quinazolinones

A palladium-catalyzed sequential cyclization/C-H activation cascade reaction of 2-amino-N'-arylbenzohydrazides with triethyl orthobenzoates has been developed, providing indazolo[3,2-b]quinazolinones in good to high yields. Two key intermediates of the reaction, 2-phenyl-3-(phenylamino)quinazolinone and C-H insertion palladacycle, were isolated, and their structures were unambiguously confirmed by X-ray crystallography. This method represents an unprecedented example of a halogen-free protocol to access indazolo[3,2-b]quinazolinones. Moreover, this chemistry also provides a useful tool for the discovery of fluorescent materials.