Stereospecific Copper(II)-Catalyzed Tandem Ring Opening/Oxidative Alkylation of Donor–Acceptor Cyclopropanes with Hydrazones: Synthesis of Tetrahydropyridazines
Aerobic copper(II)-catalyzed tandem ringopening and oxidative C–H alkylation of donor–acceptorcyclopropanes with bisaryl hydrazones is accomplished to produce tetrahydropyridazines, in which copper(II) plays dual role as a Lewis acid as well as redox catalyst. The reaction is stereospecific, and optically active cyclopropanes can be reacted with high optical purities (89–98% enantiomeric excess)
Enantio‐, Diastereo‐ and Regioselective Synthesis of Chiral Cyclic and Acyclic
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‐Difluoromethylenes by Palladium‐Catalyzed [4+2] Cycloaddition
A Pd-catalyzed asymmetric [4+2] cycloaddition between substituted-2-alkylidenetrimethylene carbonates and cyclic or acyclic gem-difluoroalkyl ketones enabled the synthesis of chiral gem-difluoromethylene compounds. A novel phosphoramidite ligand, which contains a bulky 1,1-dinaphthylmethanamino moiety, was the key to providing high yield products with excellent enantio-, diastereo-, and regioselectivity
Iron-catalyzed cascade C–C and C–O bond formation of 2,4-dienals with donor–acceptor cyclopropanes (DACs) has been developed to furnish hexahydrocyclopentapyrans. Opticallyactive DACs can be coupled stereospecifically (>97% ee). Chirality transfer, use of iron-catalysis and substrate scope are the salient practical features.
Rare alkenylalanes are prepared by Cp2TiCl2 or Cp-2*grCl(2) (Cp = eta-C5H5; CP* = eta-C5Me5) catalysed addition of HAlCl2 center dot(THF)(2) to terminal alkynes ((RC)-C-1 CH; R-1 = alkyl). Use of minimum head-volume sealed vials maximises the hydroalumination yields of volatile alkynes. Facile 1,4-addition of the resultant alkenylalanes to unsaturated malonates (RCH)-C-2=C(CO2R3)(2) (R-2 = alkyl, aryl, R-3 = alkyl) is observed providing rapid and convenient access to the addition products. (C) 2014 Elsevier Ltd. All rights reserved.
Indium(III)-Catalyzed Knoevenagel Condensation of Aldehydes and Activated Methylenes Using Acetic Anhydride as a Promoter
amount of InCl3 and aceticanhydride remarkably promotes the Knoevenagel condensation of a variety of aldehydes and activated methylene compounds. This catalytic system accommodates aromatic aldehydes containing a variety of electron-donating and -withdrawing groups, heteroaromatic aldehydes, conjugate aldehydes, and aliphatic aldehydes. Central to successfully driving the condensation series is the formation