Synthesis of Spirocyclohexadienones via Palladium-Catalyzed Dearomatization of Dibenzoxaborins.

The development of Pd(II)-catalyzed dearomatization transformation of dibenzoxaborins with alkynes triggered by transmetalation from boron to palladium has been achieved, leading to the synthesis of spirocyclohexadienones, an important skeleton demonstrating potential biomedical utility. The [3 + 2] spiroannulation exhibits remarkable regioselectivity and broad substrate scope under mild reaction conditions. This methodology employs dibenzoxaborin as a substrate to establish the formal dearomatization of 2-phenylphenol, which poses a formidable energy barrier to the destruction of aromaticity.

RhodiumIII-catalyzed remote difunctionalization of arenes assisted by a relay directing group.

Rhodium-catalyzed diverse tandem twofold C-H bond activation reactions of para-olefin-tethered arenes have been realized, with unsaturated reagents such as internal alkynes, dioxazolones, and isocyanates being the coupling partner as well as a relay directing group which triggers cyclization of the para-olefin group under oxidative or redox-neutral conditions. The reaction proceeded via initial ortho-C-H activation assisted by a built-in directing group in the arene, and the ortho-incorporation of the unsaturated coupling partner simultaneously generated a relay directing group that allows sequential C-H activation at the meta-position and subsequent cyclization of the para-olefins. The overall reaction represents C-C or N-C difunctionalization of the arene with the generation of diverse 2,3-dihydrobenzofuran platforms. The catalytic system proceeded with good efficiency, simple reaction conditions, and broad substrate scope. The diverse transformations of the products demonstrated the synthetic utility of this tandem reaction.

Rhodium(iii)-catalyzed asymmetric [4+1] spiroannulations of O-pivaloyl oximes with α-diazo compounds.

Chiral RhIII catalysts can catalyze the asymmetric [4+1] spiroannulation of O-pivaloyl oximes with α-diazo homophthalimides under redox-neutral and acid/base-neutral conditions, leading to formation of chiral spirocyclic imines as a result of C-H activation and N-O cleavage. The reaction proceeded with high efficiency and features broad substrate scope, mild reaction conditions, and high to excellent enantioselectivities.

Rhodium-Catalyzed Atroposelective Construction of Indoles via C-H Bond Activation.

Reported herein is the rhodium(III)-catalyzed C-H activation of anilines bearing an N-isoquinolyl directing group for oxidative [3+2] annulation with four classes of internal alkynes, leading to atroposelective indole synthesis via dynamic kinetic annulation with C-N reductive elimination constituting the stereo-determining step. This reaction proceeds under mild conditions with high regio- and enantioselectivity and functional group compatibility.

Rh(III)-Catalyzed Oxidative Spirocyclization of Isoquinolones with α-Diazo-1,3-indandiones.

Rh(III)-catalyzed site-selective oxidative spirocyclization reactions of isoquinolones with α-diazo-1,3-indandiones leading to three kinds of spiro compounds by employing isoquinolones with different structural features or tuning the reaction parameters are presented. In addition, a plausible catalytic cycle is proposed on the basis of control experimental results and density functional theory calculations. Finally, the diverse transformations of the spiro products into other complex skeletons demonstrate the synthetic utility of this protocol.

Rh(III)-Catalyzed Oxidative Annulation of Isoquinolones with Diazoketoesters Featuring an in Situ Deacylation: Synthesis of Isoindoloisoquinolones and Their Transformation to Rosettacin Analogues.

A novel and practical procedure for the preparation of isoindolo[2,1- b]isoquinoline-7-carboxylate derivatives through a Rh(III)-catalyzed oxidative [4 + 1] cycloaddition of isoquinolones with diazoketoesters followed by an in situ deacylation reaction is disclosed. Intriguingly, the title compounds could be easily converted into isoindolo[2,1- b]isoquinolin-5(7 H)-ones via de-esterification, which are rosettacin analogues and frequently found in various natural alkaloids and synthetic drug molecules.