Atroposelective Synthesis of Axially Chiral Diaryl Ethers by N-Heterocyclic-Carbene-Catalyzed Sequentially Desymmetric/Kinetic Resolution Process.

We describe herein an N-heterocyclic-carbene-catalyzed atroposelective synthesis of axially chiral diaryl ethers. Through a sequentially enantioselective desymmetric process and a kinetic resolution process, the products could be constructed in good yields with excellent enantiopurities. Both alcohols and phenols were compatible with this catalytic system. The axially chiral carboxylic acids derived from the esters were proven to be potential chiral ligands for asymmetric synthesis, for example, Rh(III)-catalyzed enantioselective C-H functionalization.

Rh(III)-Catalyzed Oxidative C-H Activation/Annulation of Salicylaldehydes with Masked Enynes for the Synthesis of Chromones.

A rhodium(III)-catalyzed oxidative C-H activation/annulation of salicylaldehydes with propargylic acetates has been developed for the regioselective synthesis of 3-vinyl chromones in good yields with broad functional group tolerance. 3-Vinyl chromones were converted into biologically active benzo[c]xanthone by I2-mediated oxidative electrocyclization.

Copper-Catalyzed Enantioselective and Regiodivergent Allylation of Ketones with Allenylsilanes.

We report herein a regiodivergent and enantioselective allyl addition to ketones with allenylsilanes through copper catalysis. With the combination of CuOAc, a Josiphos-type bidentate phosphine ligand and PhSiH3 , allyl addition to a variety of ketones furnishes branched products in excellent enantioselectivities. The regioselectivity is completely reversed by employing the P-stereogenic ligand BenzP*, affording the linear products with excellent enantioselectivities and good Z-selectivities. The linear Z-product could be converted to E-product via a catalytic geometric isomerization of the Z-alkene group. The silyl group in the products could provide a handle for downstream elaboration.

Palladium-Catalyzed Defluorinative Alkylation of gem-Difluoroalkenes with Cyclopropanols: Stereoselective Synthesis of γ-Fluorinated γ,δ-Unsaturated Ketones.

A palladium-catalyzed defluorinative alkylation of gem-difluoroalkenes with cyclopropyl alcohols was developed. A range of γ-fluorinated γ,δ-unsaturated ketones were constructed in good yields with excellent stereoselectivities. In addition, by base-mediated intramolecular nucleophilic vinylic substitution (SNV), the products could be further transformed to 2,5-dimethylenetetrahydrofurans and analogues with excellent stereoselectivities.