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.

Pd-Catalyzed Asymmetric 5-exo-trig Cyclization/Cyclopropanation/Carbonylation of 1,6-Enynes for the Construction of Chiral 3-Azabicyclo[3.1.0]hexanes.

We herein disclose a mild and efficient access to chiral 3-azabicyclo[3.1.0]hexanes via a Pd-catalyzed asymmetric 5-exo-trig cyclization/cyclopropanation/carbonylation of 1,6-enynes. Various nucleophiles, such as alcohols, phenols, amines and water, are well compatible with the reaction system. This reaction forms three C-C bonds, two rings, two adjacent quaternary carbon stereocenters as well as one C-O/C-N bond with excellent regio- and enantioselectivities. The products could be further functionalized to generate a library of 3-azabicyclo[3.1.0]hexane frameworks.

(Z)-Selective Synthesis of Bromofluoroalkenes via the TMSCF2Br-Mediated Tandem Reaction with para-Quinone Methides.

We report herein a tandem reaction of para-quinone methides with TMSCF2Br to construct bromofluoroalkenes in a Z-selective manner. While TMSCF2Br has been documented as the precursor of difluoro carbene, it exhibits another possibility in this transformation, a formal bromofluoro carbene surrogate. The alkenyl bromide unit of the products could directly engage in a variety of transformations.

Synthesis of pyranopyrazoles with a chiral quaternary carbon stereocenter via copper-catalyzed enantioselective [3 + 3] cycloaddition.

A copper-catalyzed enantioselective [3 + 3] cycloaddition of propargyl carbonates and pyrazolones has been disclosed. This reaction provided an efficient route to synthesize pyranopyrazoles containing a chiral quaternary carbon stereocenter in good yields with good to excellent enantioselectivities. In addition, the hydroxyl group in the products could be conveniently transformed into a variety of functional groups, such as aldehyde, nitrile, alkene, ester and amide groups, which further increased the synthetic value of this reaction.