Rh-Catalyzed Cascade C–C/Colefin–H Activations and Mechanistic Insight

Type I [4σ+4π] versus [4σ+4π-1] Cycloaddition To Access Medium-Sized Carbocycles and Discovery of a Liver X Receptor β-Selective Ligand

Transition-metal-catalyzed [4+4] cycloaddition leading to cyclooctanoids has centered on dimerization between 1,3-diene-type substrates. Herein, we describe a [4σ+4π-1] and [4σ+4π] cycloaddition strategy to access 7/8-membered fused carbocycles through rhodium-catalyzed coupling between the 4σ-donor (benzocyclobutenones) and pendant diene (4π) motifs. The two pathways can be controlled by adjusting the solvated CO concentration. A broad range (>40 examples) of 5-6-7 and 5-6-8 polyfused carbocycles was obtained in good yields (up to 90 %). DFT calculations, kinetic monitoring and 13C-labeling experiments were carried out, suggesting a plausible mechanism. Notably, one 5-6-7 tricycle was found to be a very rare, potent, and selective ligand for the liver X receptor β (KD=0.64 μM), which is a potential therapeutic target for cholesterol-metabolism-related fatal diseases.

Route to Functionalized Tetrahydrobenzo[d]azepines via Re2O7-Mediated Intramolecular Friedel-Crafts Reaction

We describe a Re2O7-mediated intramolecular dehydrative Friedel-Crafts reaction for the efficient synthesis of various benzo-fused heterocycles such as benzazepines and benzazocines. This process is characterized by a broad substrate scope, mild reaction conditions, high efficiency, and high atom economy. The potential application of this methodology was exemplified by the facile preparation of a NMDA antagonist as well as a key intermediate en route to SKF 38393.

Synthesis of Tetrahydro-indolones through Rh(III)-Catalyzed [3 + 2] Annulation of Enaminones with Iodonium Ylides

An unprecedented protocol for a Rh(III)-catalyzed [3 + 2] annulation from simple and readily available enaminones and iodonium ylides has been developed. The novel strategy allows for access to a new class of structurally diverse tetrahydro-indolones with high efficiency and a broad substrate scope. In addition, this transformation represents the first example of the selective Rh(III)-catalyzed alkenyl C-H bond functionalization and annulation of enaminones. Finally, the potential applications of this protocol are demonstrated through gram-scale reaction and late-stage modification.

Rh(III)-Catalyzed [3 + 2] Annulation/Pinacol Rearrangement Reaction of Enaminones with Iodonium Ylides: Direct Synthesis of 2-Spirocyclo-pyrrol-3-ones

A novel Rh(III)-catalyzed cascade alkenyl C-H activation/[3 + 2] annulation/pinacol rearrangement reaction of enaminones with iodonium ylides has been developed. This methodology provides a new and straightforward synthetic strategy to afford highly functionalized 2-spirocyclo-pyrrol-3-ones in satisfactory yield from readily available starting materials under mild conditions. Moreover, gram-scale reactions and further derivatization experiments are implemented to demonstrate the potential utility of this developed approach.

Chemo- and Diastereoselective Acylfluorination of Nonactivated Olefins to Access Benzo[b]azepines

Here, we describe a transition-metal-free condition that realized the intramolecular acylfluorination of unactivated olefins. It was designed to access seven-membered-ring-containing benzo[b]annulenones from readily prepared 2-allylamino benzoic acids. The formation of a broad scope of electronically and sterically varied benzo[b]annulenones was demonstrated (>30 examples, up to 88% yield and >20:1 dr ratio). Mechanistic studies indicated that the in situ formed XatlFluor-E-activated anhydride was the active species and induced an electrophilic 7-endo-trig cyclization, followed by fluoride capture of the cation.

2-Pyridinylmethyl borrowing: base-promoted C-alkylation of (pyridin-2-yl)-methyl alcohols with ketones via cleavage of unstrained C(sp3)–C(sp3) bonds

2-Pyridinylmethyl Borrowing: Transition-metal-free 2-pyridinylmethyl borrowing C-alkylation of alcohols access to ketones is developed. This unstrained C(sp3)–C(sp3) bonds cleavage of unactivated alcohols avoids the use of transition metals.

Ru(ii)-Catalyzed C–H activation/annulation reactions of N-aryl-pyrazolidinones with sulfoxonium ylides: synthesis of cinnoline-fused pyrazolidinones

The first Ru(ii)-catalyzed cascade C–H activation/annulation reactions of N-aryl-pyrazolidinones with sulfoxonium ylides are reported.