Rhodium(III)-catalyzed oxidative olefination of pyridines and quinolines: multigram-scale synthesis of naphthyridinones

Recent advances in positional-selective alkenylations: removable guidance for twofold C–H activation

Recent advances in transition-metal catalyzed positional-selective alkenylations via twofold C–H activation directed by removable or traceless directing groups are reviewed.

Expeditious synthesis of pyrano[2,3,4-de]quinolines via Rh(iii)-catalyzed cascade C–H activation/annulation/lactonization of quinolin-4-ol with alkynes

One-step synthesis of tetracyclic pyrano[2,3,4-de]quinolones via Rh(iii)-catalyzed cascade C–H activation/annulation/lactonization is described.

Transition-metal-free dehydrogenation coupling of pyridinium through a self-promoted hydride transfer process

An intramolecular dehydrogenation coupling between phenol and pyridinium through a unique substrate self-promoted hydride transfer process has been developed.

Transition metal-catalyzed site- and regio-divergent C–H bond functionalization

The regioselectivity of C–H functionalization reactions can be redirected to obtain regioisomeric products form the same starting materials.

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.

Recent Advances in the C-H-Functionalization of the Distal Positions in Pyridines and Quinolines

This review summarizes recent developments in the C-H-functionalization of the distal positions of pyridines, quinolines and related azaheterocycles. While the functionalization of the C2 position has been known for a long time and is facilitated by the proximity to N1, regioselective reactions in the distal positions are more difficult to achieve and have only emerged in the last decade. Recent advances in the transition metal-catalyzed distal C-H-functionalization of these synthetically-important azaheterocycles are discussed in detail, with the focus on the scope, site-selectivity and mechanistic aspects of the reactions.

Mechanistic Understanding of the Divergent Reactivity of Cyclopropenes in Rh(III)-Catalyzed C-H Activation/Cycloaddition Reactions of N-Phenoxyacetamide and N-Pivaloxybenzamide

Density functional theory calculations were conducted to develop a mechanistic understanding of the Rh(III)-catalyzed C-H activation/cycloaddition reactions of N-phenoxyacetamide and N-pivaloxybenzamide with cyclopropenes, and insights into the substrate-dependent chemoselectivity were provided. The results showed that the divergence originated from the different reactivity of the seven-membered rhodacycles from the insertion of cyclopropene into the Rh-C bond. In reactions of N-pivaloxybenzamide, such an intermediate undergoes the pivalate migration to form a cyclic Rh(V)-nitrenoid intermediate in a reaction that is easier than the opening of the three-membered ring by β-carbon elimination, leading finally to a tricyclic product with retention of the cyclopropane moiety by facile reductive elimination. While similar Rh(V)-nitrenoid species could also be possibly formed in Cp*Rh(III)-catalyzed reactions of N-phenoxyacetamide, the β-carbon elimination occurs more easily from the corresponding seven-membered rhodacycle intermediate and the subsequent O-N bond cleavage gives rise to an unexpected dearomatized (E)-6-alkenylcyclohexa-2,4-dienone intermediate. The E/Z isomerization of this intermediate is required for the final cyclization to 2H-chromene, and interesting metal-ligand cooperative catalysis with Rh(III) carboxylate was disclosed in the C═C double bond rotation process.

Rh(iii)-catalyzed C-H olefination of N-pentafluoroaryl benzamides using air as the sole oxidant

The oxidative olefination of a broad array of arenes and heteroarenes with a variety of activated and unactivated olefins has be achieved via a rhodium(iii)-catalyzed C-H activation reaction. The use of an N-pentafluorophenyl benzamide directing group is crucial for achieving catalytic turnovers in the presence of air as the sole oxidant without using a co-oxidant.

Cross-dehydrogenative coupling of α-C(sp3)–H of ethers/alkanes with C(sp2)–H of heteroarenes under metal-free conditions

A metal-free cross-dehydrogenative coupling method between α-oxyalkyl/alkyl radicals and electron deficient heteroarenes is reported.

Sulphuric acid immobilized on silica gel (H2SO4–SiO2) as an eco-friendly catalyst for transamidation

A novel method of transamidation of carboxamides with amines using catalytic amounts of H₂SO₄–SiO₂ under solvent-free conditions has been developed. The scope of the methodology has been demonstrated with primary and secondary amines.

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.

Discovery of novel Bcr-Abl inhibitors with diacylated piperazine as the flexible linker

Forty-two compounds with flexible diacylated piperazine linkers were designed, synthesized and evaluated as novel Bcr-Abl inhibitors.

Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H)-ones via microwave-activated inverse electron-demand Diels-Alder reactions

Substituted 3,4-dihydro-1,8-naphthyridin-2(1H)-ones have been synthesized with the inverse electron-demand Diels-Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels-Alder reaction to yield 5-aryl-3,4-dihydro-1,8-naphthyridin-2(1H)-ones by an efficient synthetic route.

Rh(iii)-catalyzed regioselective hydroarylation of alkynes via directed C–H functionalization of pyridines

Rh(iii)-catalyzed C-3 selective alkenylation of pyridines via hydroarylation of alkynes has been developed. The reaction shows high regioselectivity, high yield and good functional group tolerance, providing a convenient strategy for the synthesis of trisubstituted alkenes.