A Tunable Class of Chiral Cp Ligands for Enantioselective Rhodium(III)-Catalyzed C–H Allylations of Benzamides

Asymmetric synthesis of α-branched amines via Rh(III)-catalyzed C-H bond functionalization

The first asymmetric intermolecular addition of non-acidic C-H bonds to imines is reported. The use of the activating N-perfluorobutanesulfinyl imine substituent is essential for achieving sufficient reactivity and provides outstanding diastereoselectivity (>98:2 dr). Straightforward removal of the sulfinyl group with HCl yields the highly enantiomerically enriched amine hydrochlorides.

Modular assembly of ring-fused and π-extended phenanthroimidazoles via C-H activation and alkyne annulation

π-Extension of 2-aryl-phenanthroimidazoles via rhodium(III)-catalyzed C-H activation and alkyne annulation is developed. This method enables rapid, practical and modular assembly of diverse ring-fused phenanthroimidazoles, including an unusual rearrangement product using aryl-alkyl asymmetric alkyne and a thiophene fused product which could serve as a Fe(3+) fluorescent probe. The feasibility of the one-pot synthesis and ruthenium(II)-catalyzed versions of this reaction was also verified.

Aromatic homologation by non-chelate-assisted Rh(III)-catalyzed C-H functionalization of arenes with alkynes

Larger condensed arenes are of interest owing to their electro- and photochemical properties. An efficient synthesis is the catalyzed aromatic annulation of a smaller arene with two alkyne molecules. Besides difunctionalized starting materials, directed C-H functionalization can be used for such aromatic homologation. However, thus far the requirement of either pre-functionalized substrates or suitable directing groups were limiting this approach. Herein, we describe a rhodium(III)-catalyzed method allowing the use of completely unbiased arenes and internal alkynes. The reaction works best with copper(II) 2-ethylhexanoate and decabromodiphenyl ether as the oxidant combination. This aromatic annulation tolerates a variety of functional groups and delivers homologated condensed arenes. Aside from simple benzenes, naphthalenes and higher condensed arenes provide access to highly substituted and highly soluble acenes structures having important electronic and photophysical properties.

Rhodium(iii)-catalysed decarbonylative coupling of maleic anhydrides with alkynes

Rhodium(iii)-catalysed decarbonylative coupling of substituted maleic anhydrides with internal alkynes gives tri- and tetrasubstituted α-pyrones.

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.

Rhodium(III)-catalyzed intramolecular hydroarylation, amidoarylation, and Heck-type reaction: three distinct pathways determined by an amide directing group

Three different Rh(III)-catalyzed reaction pathways of a wide variety of tethered alkenes can be accessed through the change of the amide directing group. This provides an efficient route to a myriad of complex polycyclic products, many containing newly-formed all-carbon quaternary centers. Amidoarylations can highly diastereoselectively deliver products with up to three contiguous stereocenters.

Room-temperature synthesis of trisubstituted allenylsilanes via regioselective C-H functionalization

A Rh(III)-catalyzed o-C-H bond functionalization-based allenylation reaction of allenylsilanes 2 with N-methoxybenzamides 1 affords poly-substituted allenylsilanes with a wide range of attractive functional groups in moderate to excellent yields under very mild conditions (20 °C, compatible with ambient air and moisture). Those products may be transformed to different products with attractive structural features. Careful mechanistic studies suggest the reaction proceeds via o-rhodation, regioselective insertion, and β-H elimination.

Iron-catalyzed ortho-allylation of aromatic carboxamides with allyl ethers

Arenes possessing an N-(quinolin-8-yl)amide directing group are ortho-allylated with allyl phenyl ether in the presence of an iron/diphosphine catalyst and an organometallic base at 50-70 °C. The reaction proceeds via fast iron-catalyzed C-H activation, followed by reaction of the resulting iron intermediate with the allyl ether in γ-selective fashion.

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.

Synthesis of functionalized spiroindolines via palladium-catalyzed methine C-H arylation

The synthesis of cyclopropyl spiroindolines is described using an intramolecular palladium(0)-catalyzed C-H functionalization of a methine C(sp(3))-H bond. This transformation can be coupled with intermolecular Suzuki couplings or direct arylations of heteroaromatics to access functionalized indoline scaffolds in a single step.