Xiaolei Huang

N‐Oxide as a Traceless Oxidizing Directing Group: Mild Rhodium(III)‐Catalyzed CH Olefination for the Synthesis of ortho‐Alkenylated Tertiary Anilines

Double role: A traceless directing group also acts as an internal oxidant in a novel Rh(III) -catalyzed protocol developed for the synthesis of ortho-alkenylated tertiary anilines. A five-membered cyclometalated Rh(III) complex is proposed as a plausible intermediate and confirmed by X-ray crystallographic analysis.

A general method to diverse cinnolines and cinnolinium salts.

Rhodium catalysis: A highly efficient and general method has been established to prepare cinnolines, cinnolinium salts, and polycyclic cinnolinium salts through the rhodium(III)-catalyzed oxidative C-H activation/cyclization of azo compounds with alkynes (see scheme). Key features of this methodology include the unprecedented capacity to create both cinnoline and cinnolinium frameworks.

Chelation-assisted Rh(III)-catalyzed C2-selective oxidative C–H/C–H cross-coupling of indoles/pyrroles with heteroarenes

The chelation-assisted strategy has been endowed with some novel functions in the Rh(III)-catalyzed dehydrogenative coupling of indoles/pyrroles with heteroarenes. While the reaction conditions used are rather common, the strategy can close the homo-coupling pathway of each coupling partner, and dramatically extend substrate scope along with the exclusive indole or pyrrole C2-site selectivity. This is the first example describing that a catalytic system allows the oxidative C–H/C–H hetero-coupling not only between two electron-rich heteroarenes but also between electron-deficient and electron-rich heteroarenes, showing a further beneficial aspect of the Rh(III) catalysis.

Rhodium(III)‐Catalyzed Activation of C sp 3H Bonds and Subsequent Intermolecular Amidation at Room Temperature

Disclosed herein is a Rh(III)-catalyzed chelation-assisted activation of unreactive C(sp3)-H bonds, thus enabling an intermolecular amidation to provide a practical and step-economic route to 2-(pyridin-2-yl)ethanamine derivatives. Substrates with other N-donor groups are also compatible with the amidation. This protocol proceeds at room temperature, has a relatively broad functional-group tolerance and high selectivity, and demonstrates the potential of rhodium(III) in the promotive functionalization of unreactive C(sp3)-H bonds. A rhodacycle having a SbF6(-) counterion was identified as a plausible intermediate.

Cobalt-Catalyzed Oxidative C−H/C−H Cross-Coupling between Two Heteroarenes

The first example of cobalt-catalyzed oxidative C-H/C-H cross-coupling between two heteroarenes is reported, which exhibits a broad substrate scope and a high tolerance level for sensitive functional groups. When the amount of Co(OAc)2 ⋅4 H2 O is reduced from 6.0 to 0.5 mol %, an excellent yield is still obtained at an elevated temperature with a prolonged reaction time. The method can be extended to the reaction between an arene and a heteroarene. It is worth noting that the Ag2 CO3 oxidant is renewable. Preliminary mechanistic studies by radical trapping experiments, hydrogen/deuterium exchange experiments, kinetic isotope effect, electron paramagnetic resonance (EPR), and high resolution mass spectrometry (HRMS) suggest that a single electron transfer (SET) pathway is operative, which is distinctly different from the dual C-H bond activation pathway that the well-described oxidative C-H/C-H cross-coupling reactions between two heteroarenes typically undergo.

Rh(III)-catalyzed annulation of N-methoxybenzamides with ynesulfonamides at room temperature: a practical and efficient route to 4-aminoisoquinolone derivatives

A practical and efficient Rh(III)-catalyzed annulation of N-methoxybenzamides with ynesulfonamides for the synthesis of 4-aminoisoquinolone derivatives has been developed under external-oxidant-free conditions at room temperature. This protocol features good functional group tolerance and excellent selectivity.