High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a nonpolar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard ­reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto ester derived and an α-phenyl cyclohexanone-­derived enol carbonate

Rapid synthesis of an electron-deficient t-BuPHOX ligand: cross-coupling of aryl bromides with secondary phosphine oxides

Herein an efficient and direct copper-catalyzed coupling of oxazoline-containing aryl bromides with electron-deficient secondary phosphine oxides is reported. The resulting tertiary phosphine oxides can be reduced to prepare a range of PHOX ligands. The presented strategy is a useful alternative to known methods for constructing PHOX derivatives

A Catalytic, Asymmetric Formal Synthesis of (+)-Hamigeran B

A concise asymmetric, formal synthesis of (+)-hamigeran B is reported. A Pd-catalyzed, decarboxylative allylic alkylation, employing a trifluoromethylated derivative of t-BuPHOX, is utilized as the enantioselective step to form the critical quaternary carbon center in excellent yield and enantioselectivity. The product is converted in three steps to a late-stage intermediate previously used in the synthesis of hamigeran B

Asymmetric Morita−Baylis−Hillman Reactions Catalyzed by Chiral Brønsted Acids

Chiral BINOL-derived Brønsted acids catalyze the enantioselective asymmetric Morita−Baylis−Hillman (MBH) reaction of cyclohexenone with aldehydes. The asymmetric MBH reaction requires 2−20 mol % of the chiral Brønsted acid 2e or 2f and triethylphosphine as the nucleophilic promoter. The reaction products are obtained in good yields (39−88%) and high enantioselectivities (67−96% ee). The Brønsted-acid-catalyzed reaction is the first example of a highly enantioselective asymmetric MBH reaction of cyclohexenone with aldehydes

Hafnium Amidoquinoline Complexes: Highly Active Olefin Polymerization Catalysts with Ultrahigh Molecular Weight Capacity

The preparation and characterization of a new class of polyolefin procatalysts is described. Hafnium tribenzyl procatalysts, supported by amidoquinoline ligands, were prepared in two steps from commercially available materials. Solid-state structures, determined by single-crystal X-ray analyses, revealed that all the hafnium complexes display approximate trigonal-bipyramidal geometry around the metal center. The complexes were evaluated in an ethylene/1-octene copolymerization study and were found to be highly active at elevated temperatures (120 °C). The best catalyst, derived from ((2,6-dimethylphenyl)­(2,4-dimethylquinolin-8-yl)­amino)­tribenzylhafnium (6d), compares favorably to previously reported systems supported by bidentate nitrogen-based ligands. In particular, this catalyst exhibits very high molecular weight capacity and high catalytic activity, with a moderate 1-octene response. Alkyl substitution at the carbon ortho to the quinolino nitrogen was found to be an important factor for improving polymer compositional homogeneity, as evidenced by a narrowing of the polydispersity index and a single melting temperature in the resulting copolymer