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

Oxidative Free-Radical C(sp2)-H Bond Chlorination of Enaminones with LiCl: Access to Highly Functionalized α-Chlorinated Enaminones

An oxidative free-radical C(sp2)-H bond chlorination strategy of enaminones has been developed by using LiCl as a chlorinating reagent and K2S2O8 as an oxidant. This transformation provides a new and straightforward synthetic methodology to afford highly functionalized α-chlorinated enaminones with a Z-configuration in good to excellent yields.

Accessing 7,8-Dihydroquinoline-2,5-diones via Rh-Catalyzed Olefinic C-H Activation/[4+2] Cyclization

Herein, we report a rhodium-catalyzed C-H activation/[4+2] cyclization reaction between α,β-unsaturated amides and iodonium ylides for the synthesis of novel 7,8-dihydroquinoline-2,5-diones and analogues. This protocol provides a series of pyridones fused with saturated cycles with good functional group compatibility, good water and air tolerance, and good to excellent yields under mild and green reaction conditions. Additionally, scale-up synthesis can be smoothly performed with as low as 0.25 mol % catalyst loading. Recycling experiments and different transformation experiments were also carried out to demonstrate the potential synthetic utility of this protocol.

Rh(III)-catalyzed C(sp2)-H functionalization/[4+2] annulation of oxadiazolones with iodonium ylides to access diverse fused-isoquinolines and fused-pyridines

In this study, a Rh(III)-catalyzed C-H/N-H [4+2] annulation of oxadiazolones with iodonium ylides has been developed, which afforded a series of diverse fused-isoquinolines and fused-pyridines in moderate to high yields. These divergent synthesis protocols featured mild conditions, broad substrate scope, and functional-group compatibility. In addition, scale-up synthesis, related applications and preliminary mechanistic explorations were also accomplished.

Divergent Synthesis of 2-Chromonyl-3-hydrazono-chromones and 2-Alkoxy-3-hydrazono-chromones through Switchable Annulation Reactions of o-Hydroxyphenylenaminones with Aryldiazonium Salts

An unprecedented selective chromone annulation reaction controlled by solvent for the divergent synthesis of two types of 2,3-disubstituted chromone skeletons has been developed. A variety of 2-chromonyl-3-hydrazono-chromones and 2-alkoxy-3-hydrazono-chromones were constructed efficiently from readily available o-hydroxyphenylenaminones (o-HPEs) and aryldiazonium salts at room temperature. This strategy is highly chemoselective and features mild reaction conditions, broad substrate scope, broad functional group tolerance, easy gram-scale preparation, and simple filtration to obtain the pure products without tedious column chromatography.

Switchable Skeletal Rearrangement of Hexahydro-4H-indol-4-ones: Divergent Synthesis of Dihydroxy-4H-cyclopenta[b]pyridin-4-ones and 8-Alkenyl Oxepane-2,6-diones

An unprecedented base-controlled selective skeletal rearrangement reaction of hexahydro-4H-indol-4-ones has been developed. In this protocol, highly functionalized dihydroxy-4H-cyclopenta[b]pyridin-4-ones and 8-alkenyl oxepane-2,6-diones were prepared with a broad substrate scope and high chemoselectivity in moderate to excellent yields selectively by modulating LiOH and Et3N. In addition, the newly formed 8-alkenyl oxepane-2,6-dione scaffolds could be easily further derivatized to 5-(pyrrol-2-yl)dihydrofuran-2(3H)-ones through a rare intramolecular rearrangement reaction.

Copper-Catalyzed Oxidative [3 + 2] Cycloaddition of Enamines and Pyridotriazoles toward Indolizines

An efficient copper catalytic system has been established for the synthesis of highly functional indolizines through oxidative [3 + 2] cycloaddition of enamines and pyridotriazoles. This modular platform is compatible with a broad range of functional groups, including natural and complex skeletons, allowing for late-stage modifications. It features a step-economical, highly regioselective, and easy-handling procedure and has been applied in constructing small molecules of potent activity toward inhibiting the VEGF-NRP1 interaction through a one-pot reaction of pyridotriazoles, amines, and aldehydes.

Tf2O-Mediated Tandem Reaction of Enaminones for the Synthesis of Functionalized Conjugated-Enals/β-Naphthalaldehydes

A highly efficient and regioselective method for constructing functionalized conjugated enals via the Tf2O-mediated tandem reaction of enaminones with thiophenols has been described. Chain products with excellent stereoselectivity could be obtained through substrate regulation. Additionally, a feasible method for synthesizing β-naphthalaldehydes through PhSO2Na/DABCO promoting hydrogen atom transfer process has also been reported here. Mechanism studies have shown that 2-formyl vinyl triflate 8 and sulfonylated enal 9 were the key intermediates in this process.

Rh(III)-catalyzed selective mono- and dual-functionalization/cyclization of 1-aryl-5-aminopyrazoles with iodonium ylides

An efficient Rh(III)-catalyzed selective mono- and dual-C-H bond functionalization/cyclization with iodonium ylide as a single coupling partner was demonstrated, in which fused benzodiazepine skeletons were obtained in excellent yields. This method greatly improved an effective approach to dual C-H unsymmetrical functionalization.