Enantioselective 1,4-Addition of Aliphatic Grignard Reagents to Enones Catalyzed by Readily Available Copper(I) thiolates derived from TADDOL. Preliminary communication

Two simple thiols derived from the parent TADDOL, α,α,α′,α′ tetraphenyl-2,2-dimethyl-1,3-clioxolan-4,5-dimethanol, are used to prepare Cu¹ complexes C and D to catalyze (0.05 equiv.) 1,4-additions of Grignard reagents RMgCl to cyclic enones with enantioselectivities which are comparable to or better than previously reported (enantiomer ratios up to 92:8).     

Short expressions of permutations as products and cryptanalysis of the Algebraic Eraser

On March 2004, Anshel, Anshel, Goldfeld, and Lemieux introduced the Algebraic Eraser scheme for key agreement over an insecure channel, using a novel hybrid of infinite and finite noncommutative groups. They also introduced the Colored Burau Key Agreement Protocol (CBKAP), a concrete realization of this scheme.     

X-Ray, Molecular Diffusion, and NOESY NMR Studies of Chiral, Tetranuclear Cu(I) Catalysts Based on Monodentate Thiol Analogues of TADDOL

The new, stable, chiral thiol-TADDOL Cu(I) catalysts 1 (X=OH, OMe, NMe(2)) reveal an unexpected monodentate complexation mode, both in solution and in the solid state. For the first time, the aggregation state of organocopper complexes has been determined by NMR diffusion measurements. NOESY NMR data on model isocyanide Cu complexes reveal a different conformation of the TADDOL moiety as a function of the second potential donor group. TADDOL=alpha,alpha,alpha',alpha'-tetraaryl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol.     

Dioxygen reactivity of new bispidine-copper complexes

The reactivity of copper complexes of three different second-generation bispidine-based ligands (bispidine = 3,7-diazabicyclo[3.3.1]nonane; mono- and bis-tetradentate; exclusively tertiary amine donors) with dioxygen [(reversible) binding of dioxygen by copper(I)] is reported. The UV-vis, electrospray ionization mass spectrometry, electron paramagnetic resonance, and vibrational spectra (resonance Raman) of the dioxygen adducts indicate that, depending on the ligand and reaction conditions, several different species (mono- and dinuclear, superoxo, peroxo, and hydroperoxo), partially in equilibrium with each other, are formed. Minor changes in the ligand structure and/or experimental conditions (solvent, temperature, relative concentrations) allow switching between the different forms. With one of the ligands, an end-on peroxodicopper(II) complex and a mononuclear hydroperoxocopper(II) complex could be characterized. With another ligand, reversible dioxygen binding was observed, leading to a metastable superoxocopper(II) complex. The amount of dioxygen involved in the reversible binding to Cu(I) was determined quantitatively. The mechanism of dioxygen binding as well as the preference of each of the three ligands for a particular dioxygen adduct is discussed on the basis of a computational (density functional theory) analysis.