A magnesium-catalyzed regiodivergent C–Obond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain
Kinetic Resolution of Hydroperoxides with Enantiopure Phosphines: Preparation of Enantioenriched Tertiary Hydroperoxides
作者:Tom G. Driver、Jason R. Harris、K. A. Woerpel
DOI:10.1021/ja070482f
日期:2007.4.1
kinetic resolution strategy capable of accessing opticallyactivetertiary hydroperoxides is reported. Readily accessible tertiary hydroperoxides are resolved with commercially available (R)- or (S)-xylyl-PHANEPHOS with selectivity factors as large as 37. The resulting bis(phosphineoxide) can be recycled in high yields. The isolated mono(phosphineoxide) intermediate resolved hydroperoxides with the
A chiral zinc complex of salen was found to be an efficient catalyst for the phenyl transfer of organozinc reagent to aromaticaldehydes and ketones. High enantioselectivities were obtained in reactions of both aromaticaldehydes and ketones (up to 97% and 92% ee, respectively).
Highly Enantioselective Catalytic Phenylation of Ketones with a Constrained Geometry Titanium Catalyst
作者:Celina García、Patrick J. Walsh
DOI:10.1021/ol0352963
日期:2003.10.1
[reaction: see text] The catalytic asymmetric addition of phenyl groups from diphenylzinc to ketones is reported. The catalyst, generated from a dihydroxy bis(sulfonamide) ligand and titanium tetraisopropoxide, gives good to excellent enantioselectivities with a range of substrates.
A highly efficient enantioselective organozinc (R2Zn) addition to ketones catalyzed by chiral phosphoramide-Zn(II) complexes (1-10 mol %) has been developed. These complexes serve as conjugate Lewis acid-Lewis base catalysts. Chiral phosphoramides are derived from an inexpensive natural amino acid (i.e., L-valine). From a variety of nonactivated aromatic and aliphatic ketones, the corresponding optically