Ligand-Enabled Alkynylation of C(sp3 )-H Bonds with Palladium(II) Catalysts

The palladium(II)-catalyzed β- and γ-alkynylation of amide C(sp³ )-H bonds is enabled by pyridine-based ligands. This alkynylation reaction is compatible with substrates containing α-tertiary or α-quaternary carbon centers. The β-methylene C(sp³ )-H bonds of various carbocyclic rings were also successfully alkynylated.

Rhodium(iii)-catalyzed directed C–H benzylation and allylation of indoles with organosilicon reagents

Rhodium(iii)-catalyzed C2-benzylation and allylation of indoles with organosilicon reagents via chelation-assisted C–H activation has been developed.

Site-selective Cp*Rh(iii)-catalyzed C–H amination of indolines with anthranils

The pyrimidinyl-directed C–H functionalization of indolines with anthranils as amination sources under rhodium(iii) catalysis is described to afford a range of C7-aminated indoline derivatives with excellent site-selectivity and functional group compatibility.

Rh(iii)-Catalyzed direct C-7 amination of indolines with anthranils

An effective and fascinating method has been developed for direct C-7 amination of indolines under Rh(iii) catalysis with anthranils.

Electronic Nature of Ketone Directing Group as a Key To Control C-2 vs C-4 Alkenylation of Indoles

A novel mode of achieving site selectivity between C-2 and C-4 positions in the indole framework by altering the property of the ketone directing group is disclosed. Methyl ketone, as directing group, furnishes exclusively C-2 alkenylated product, whereas trifluoromethyl ketone changes the selectivity to C-4, indicating that the electronic nature of the directing group controls the unusual choice between a 5-membered and a 6-membered metallacycle. The screening of other carbonyl-derived directing groups reveals that strong and weak directing groups exhibit opposite selectivity. Experimental controls and deuteration experiments lend support to the proposed mechanism.

Ir(III)-catalyzed C-H alkynylation of arenes under chelation assistance

An efficient and mild Ir(III)-catalyzed, chelation assisted C-H alkynylation of arenes has been developed using hypervalent iodine alkynes as alkynylating reagents. A broad scope of N-phenyl-2-aminopyridines and 2-phenoxypyridines has been established as effective substrates for this C-H functionalization and the desired alkynylated products were isolated in moderate to high yields.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

Ru-Catalyzed selective C–H oxidative olefination with N-heteroarenes directed by pivaloyl amide

Ruthenium-catalysed C7-position alkynylation for indoline derivatives with various olefins was reported.

Ru-catalysed C–H silylation of unprotected gramines, tryptamines and their congeners

Directed and undirected Ru-catalysed C–H silylation of unprotected heteroarenes is presented which requires no protecting groups.

Iridium(iii)-catalyzed regioselective C7-sulfonamidation of indoles

Iridium(iii)-catalyzed direct C7-sulfonamidation of indoles with sulfonyl azides is described.

Regioselective Ir(iii)-catalyzed C–H alkynylation directed by 7-azaindoles

Herein we report a novel iridium(iii)-catalyzed ortho-mono-alkynylation of 7-azaindoles. The reactions proceeded highly efficiently and selectively under mild conditions over a broad range of substrates with excellent functional group tolerance.

Rh(III) and Ru(II)-catalyzed site-selective C-H alkynylation of quinolones

C2- and C5-alkynylated quinolone scaffolds are core structures of numerous biologically active molecules. Utilizing TIPS-EBX as an alkynylating agent, we have developed an efficient and site-selective C5 alkynylation of 4-quinolones that is directed by the weakly coordinating carbonyl group. In addition, Ru(II) catalyzed C2-selective alkynylation was successfully realized via N-pyrimidyl group-directed cross-couplings to access valuable C2-alkynylated 4-quinolones. This strategy provides direct access to the C2 or C5 alkynylated 4-quinolones. Furthermore, the reaction was applied to isoquinolones for C3-selective alkynylation.

Palladium-catalyzed oxalyl amide assisted direct ortho-alkynylation of arylalkylamine derivatives at δ and ε positions

Palladium-catalyzed oxalyl amide directed ortho-alkynylation of arylalkylamine derivatives via rare six- and seven-membered palladacycles has been reported.