Rh(III)-Catalyzed C-H Activation of Benzamides and Chemodivergent Annulation with Benzoxazinanones: Substrate Controlled Selectivity.

Decarboxylative annulation of propargyl carbamates with benzamides has been realized via rhodium-catalyzed C-H bond activation under mild conditions, delivering two distinct classes of heterocycles in high efficiency and selectivity under substrate control. This protocol provides a direct synthetic method for the preparation of functionalized 1,8-naphthyridines and isoindolinones.

Palladium-Catalyzed Regio- and Enantioselective Hydrophosphination of gem-Difluoroallenes.

Chiral allylic phosphines and gem-difluoroalkenes are both important structural motifs in various bioactive molecules, chiral ligands, and natural products. These two motifs are now integrated, and we herein report a straightforward and atom-economical enantioselective hydrophosphination of gem-difluoroallenes using disubstituted phosphines. A wide array of enantioenriched fluorinated allylic phosphines has been accessed with excellent regio- and enantioselectivity and high efficiency. Synthetic and catalytic applications of phosphine products have been demonstrated.

Catalytic aminomethylative etherification of N-allenamides with N,O-acetals enabled by Lewis/Brønsted acid catalysis.

A novel copper-catalyzed aminomethylative etherification of N-allenamides/alkoxyallenes with N,O-acetals has been realized under mild reaction conditions, in which every single atom of N,O-acetals is incorporated into the newly formed molecules. Furthermore, in the presence of a chiral phosphoric acid, the asymmetric aminomethylative etherification of N-allenamides has been accomplished using N,O-acetals as bifunctionalization reagents.

Rhodium-Catalyzed Atroposelective Access to Axially Chiral Olefins via C-H Bond Activation and Directing Group Migration.

Axially chiral open-chain olefins represent an underexplored class of chiral platform. In this report, two classes of tetrasubstituted axially chiral acyclic olefins have been accessed in excellent enantioselectivity and regioselectivity via C-H activation of (hetero)arenes assisted by a migratable directing group en route to coupling with sterically hindered alkynes. The coupling of indoles bearing an N-aminocarbonyl directing group afforded C-N axially chiral acrylamides with the assistance of a racemic zinc carboxylate additive. DFT studies suggest a ß-nitrogen elimination-reinsertion pathway for the directing group migration. Meanwhile, the employment of N-phenoxycarboxamide delivered C-C axially chiral enamides via migration of the oxidizing directing group. Experiments suggest that in both cases the (hetero)arene substrate adopts a well-defined orientation during the C-H activation, which in turn determines the disposition of the alkyne in migratory insertion. Synthetic applications of representative chiral olefins are demonstrated.

Tandem Reaction of Allenoate Formation and Cyclization: Divergent Synthesis of Four- to Six-Membered Heterocycles.

Tandem reactions of copper-catalyzed cross-coupling of N-substituted prop-2-yn-1-amines with diazoacetates and subsequent cyclization have been developed to prepare several types of four- to six-membered heterocycles. Copper-catalyzed allenoate formation has been proven as the key step for the diverse annulations. Importantly, on the basis of the choice of different N-protecting groups of the alkyne substrates, methods toward 5,6-dihydropiperidin-2-ones, 2-methyleneazetidines, and furan derivatives have been well established.

Rhodium-Catalyzed Regioselective N2 -Alkylation of Benzotriazoles with Diazo Compounds/Enynones via a Nonclassical Pathway.

A novel rhodium-catalyzed highly selective N2 -alkylation of benzotriazoles with diazo compounds/enynones is achieved, providing N2 -alkylated benzotriazoles in good to excellent yields and with excellent N2 selectivities. Importantly, different to traditional carbene insertion into X-H (X=N, O etc) bonds, DFT calculations disclose that this selective N2 -alkylation probably proceeds through a formal 1,3- rather than 1,2-H shift to give the final products.

Asymmetric [4 + 2]-Cycloaddition of Copper-Allenylidenes with Hexahydro-1,3,5-triazines: Access to Chiral Tetrahydroquinazolines.

A copper-catalyzed asymmetric formal [4 + 2]-cycloaddition of copper-allenylidenes and hexahydro-1,3,5-triazines has been developed, providing chiral tetrahydroquinazolines in moderate to good yields and with high enantioselectivities for most cases (up to 88% yield and 98% ee).

[3 + 2]-Cycloaddition of Azaoxyallyl Cations with Hexahydro-1,3,5-triazines: Access to 4-Imidazolidinones.

A novel base-promoted [3 + 2] cycloaddition reaction of azaoxyallyl cations with hexahydro-1,3,5-triazines has been developed, affording 4-imidazolidinones in moderate to good yields under mild reaction conditions. This simple but efficient protocol features cycloaddition of two in situ formed reactive species in the absence of a transition-metal catalyst.

Gold-catalyzed [2+2+2+2]-annulation of 1,3,5-hexahydro-1,3,5-triazines with alkoxyallenes.

An unprecedented gold-catalyzed [2+2+2+2]-annulation of 1,3,5-hexahydro-1,3,5-triazines with alkoxyallenes has been developed, providing eight-membered heterocycles in good to excellent yields. Deuterium labeling and control experiments reveal the possible reaction mechanism for this annulation.