Rh(III)-catalyzed regioselective synthesis of pyridines from alkenes and α,β-unsaturated oxime esters

Cyclometalated [Cp*M(C^X)] (M = Ir, Rh; X = N, C, O, P) complexes

Isolated and well-defined cyclometalated iridium/rhodium complexes that contain a Cp*M–C (M = Ir, Rh) bond stabilised by the intramolecular coordination of neutral donor atoms (N, C, O or P), together with their applications, were summarized.

Rhodium(iii)-catalyzed regioselective C2-amidation of indoles with N-(2,4,6-trichlorobenzoyloxy)amides and its synthetic application to the development of a novel potential PPARγ modulator

Here an efficient rhodium(iii)-catalyzed C2-amidation of indoles and its synthetic application to a new PPARγ modulator have been developed.

Practical synthesis of pyrazoles via a copper-catalyzed relay oxidation strategy

An efficient Cu-catalyzed cascade reaction involving N–O bond cleavage and C–C/C–N/N–N bond formations is developed to afford various 1,3- and 1,3,4-substituted pyrazoles.

A heavy metal- and oxidant-free, one-pot synthesis of pyridines and fused pyridines based on a Lewis acid-catalyzed multicomponent reaction

Pyridines and fused pyridines are accessible by a combination of a Lewis acid-catalyzed multicomponent reaction and aromatization involving loss of a 2-furylmethyl chain.

A new approach to pyridines through the reactions of methyl ketones with 1,2,4-triazines

A new route to prepare pyridine derivatives based on inverse electron demand Diels–Alder/retro-Diels–Alder reactions of ketones with 1,2,4-triazines is reported, which is complementary to the classical Boger reaction.

Rh(iii)-catalyzed synthesis of 1-aminoindole derivatives from 2-acetyl-1-arylhydrazines and diazo compounds in water

Rh(iii)-catalyzed synthesis of 1-aminoindole derivatives from 2-acetyl-1-arylhydrazines and diazo compounds has been developed, through tandem C–H activation, cyclization and condensation.

Straightforward assembly of benzoxepines by means of a rhodium(III)-catalyzed C-H functionalization of o-vinylphenols

Readily available o-vinylphenols undergo a formal (5 + 2) cycloaddition to alkynes when treated with catalytic amounts of [Cp*RhCl2]2 and Cu(OAc)2. The reaction, which involves the cleavage of the terminal C-H bond of the alkenyl moiety, generates highly valuable benzoxepine skeletons in a practical, versatile, and atom-economical manner. Using carbon monoxide instead of an alkyne as reaction partner leads to coumarin products which formally result from a (5 + 1) cycloaddition.

Isothiourea-mediated one-pot synthesis of functionalized pyridines

Acids to bases: The synthesis of 2,4,6-trisubstituted pyridines from (phenylthio)acetic acid and a range of α,β-unsaturated ketimines is reported. This process proceeds by intermolecular Michael addition/lactamization, thiophenol elimination, and N- to O-sulfonyl migration, giving 2-sulfonate-substituted pyridines which are readily derivatized to generate structural diversity.

Facile synthesis of unsymmetrical acridines and phenazines by a Rh(III)-catalyzed amination/cyclization/aromatization cascade

We report formal [3 + 3] annulations of aromatic azides with aromatic imines and azobenzenes to give acridines and phenazines, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine.

Rh(III)-catalyzed synthesis of multisubstituted isoquinoline and pyridine N-oxides from oximes and diazo compounds

Multisubstituted isoquinoline and pyridine N-oxides have been prepared by Rh(III)-catalyzed cyclization of oximes and diazo compounds via aryl and vinylic C-H activation. This intermolecular annulation involving tandem C-H activation, cyclization, and condensation steps proceeds under mild conditions, obviates the need for oxidants, releases N2 and H2O as the byproducts, and displays a broad substituent scope.

Catalyst-controlled divergent C-H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds with alkynes and alkenes

Achieving site-selective, switchable C-H functionalizations of substrates that contain several different types of reactive C-H bonds is an attractive objective to enable the generation of different products from the same starting materials. Herein, we demonstrate the divergent C-H functionalization of unsymmetrical 2-aryl cyclic 1,3-dicarbonyl compounds that contain two distinct, nonadjacent sites for initial C-H functionalization, where product selectivity is achieved through catalyst control. By use of a palladium-N-heterocyclic carbene complex as the precatalyst, these substrates undergo oxidative annulation with alkynes to provide spiroindenes exclusively. In contrast, a ruthenium-based catalyst system gives benzopyrans as the major products. Examples of divergent, oxidative C-H alkenylations of the same substrates are also provided.

Rhodium(III)-catalyzed C-H olefination for the synthesis of ortho-alkenyl phenols using an oxidizing directing group

By using an oxidizing directing group, a mild, efficient Rh(III) catalyzed C-H olefination reaction between N-phenoxyacetamides and alkenes was developed. This reaction provided a straightforward way for the synthesis of ortho-alkenyl phenols, and the directing group is traceless in the product.

Rh(III)/Cu(II)-cocatalyzed synthesis of 1H-indazoles through C-H amidation and N-N bond formation

Substituted 1H-indazoles can be formed from readily available arylimidates and organo azides by Rh(III)-catalyzed C-H activation/C-N bond formation and Cu-catalyzed N-N bond formation. For the first time the N-H-imidates are demonstrated to be good directing groups in C-H activation, also capable of undergoing intramolecular N-N bond formation. The process is scalable and green, with O2 as the terminal oxidant and N2 and H2O formed as byproducts. Moreover, the products could be transformed to diverse important derivatives.

Rhodium(III)-catalyzed indazole synthesis by C-H bond functionalization and cyclative capture

An efficient, one-step, and highly functional group-compatible synthesis of substituted N-aryl-2H-indazoles is reported via the rhodium(III)-catalyzed C–H bond addition of azobenzenes to aldehydes. The regioselective coupling of unsymmetrical azobenzenes was further demonstrated and led to the development of a new removable aryl group that allows for the preparation of indazoles without N-substitution. The 2-aryl-2H-indazole products also represent a new class of readily prepared fluorophores for which initial spectroscopic characterization has been performed.