Reduction of Ketones with LiAlH4 Complexes of α,α,α\u27,α\u27-Tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOLs) A Combination of Enantioselective Reduction and Clathrate Formation with a Discussion of LAH Reagents Bearing C2-Symmetrical Ligands

A complex prepared from one equivalent each of LiAlH4, EtOH and a TADDOL (α,α,α\u27,α\u27-tetraaryl-1,3-dioxolane-4,5-dimethanol) reduces aryl alkyl ketones to sec. alcohols with enantiomer ratios (er) up to 96 : 4. The chiral LAH derivative is used in two-fold excess in THF solution and at dry ice temperatures. The ability of TADDOLs to form clathrates diastereoselectively can be exploited to increase the er of the initially formed alcohols by a simple modification of the work-up procedure and hence, products of very high en- antiopurity (er 99 : 1) can be isolated. When (7i,/i)-TADDOLs (from (ZiA)-tartrate) are applied in the reaction, the 1-aryl-alkanols formed preferentially have (S) configuration, as for the products obtained with the corresponding (P)-BINOL and (P)-BIPHENOL derivatives. A common mechanistic model is discussed

self-assembly and chemical modifications of Bisphenol A on cu(111): Interplay between ordering and thermally activated stepwise deprotonation

Bisphenol A (BPA) is a chemical widely used in the synthesis pathway of polycarbonates for the production of many daily used products. Besides other adverse health effects, medical studies have shown that BPA can cause DNA hypomethylation and therefore alters the epigenetic code. In the present work, the reactivity and self-assembly of the molecule was investigated under ultra-high-vacuum conditions on a Cu(111) surface. We show that the surface-confined molecule goes through a series of thermally activated chemical transitions. Scanning tunneling microscopy investigations showed multiple distinct molecular arrangements dependent on the temperature treatment and the formation of polymer-like molecular strings for temperatures above 470 K. X-ray photoelectron spectroscopy measurements revealed the stepwise deprotonation of the hydroxy groups, which allows the molecules to interact strongly with the underlying substrate as well as their neighboring molecules and therefore drive the organization into distinct structural arrangements. On the basis of the combined experimental evidence in conjunction with density functional theory calculations, structural models for the self-assemblies after the thermal treatment were elaborated