1,1,1,3,3,3‐Hexafluoroisopropanol as a Remarkable Medium for Atroposelective Sulfoxide‐Directed Fujiwara–Moritani Reaction with Acrylates and Styrenes

Axially chiral biaryls are ubiquitous structural motifs of biologically active molecules and privileged ligands for asymmetric catalysis. Their properties are due to their configurationally stable axis, and therefore, the control of their absolute configuration is essential. Efficient access to atropo‐enantioenriched biaryl moieties through asymmetric direct C?H activation, by using enantiopure sulfoxide as both the directing group (DG) and chiral auxiliary, is reported. The stereoselective oxidative Heck reactions are performed in high yields and with excellent atropo‐stereoselectivities. The pivotal role of 1,1,1,3,3,3‐hexafluoropropanol (HFIP) solvent, which enables a drastic increase in yield and stereoselectivity of this transformation, is evidenced and investigated. Finally, the synthetic usefulness of the herein disclosed transformation is showcased because the traceless character of the sulfoxide DG allows straightforward conversions of the newly accessed, atropopure sulfoxide‐biaryls into several differently substituted axially chiral scaffolds.     

Syntheses,structures, and electrochemistry of a dinuclear compound and a mononuclear–mononuclear cocrystalline compound of uranyl(VI)

Syntheses, structures, and electrochemistry of a dialkoxo‐bridged diuranyl(VI) compound [(UO₂)₂(L¹)₂(dimethylformamide)₂] ( 1 ) and a mononuclear–mononuclear cocrystalline compound [(UO₂)(L²)(H₂O)⊂(H₂O)]·[(UO₂)(L²)(H₂O)] ( 2 ) derived from Schiff base ligands are reported (H₂L¹ = Schiff base ligand obtained on condensation of 3‐ethoxysalicylaldehyde with 2‐aminoethanol; H₂L² = N,N ′‐o ‐phenylenebis(3‐ethoxysalicylaldimine)). The compounds 1 and 2 crystallize in the space groups P 2₁/c and P 1, respectively. Compound 1 is a dialkoxo‐bridged dinuclear compound of uranium(VI) containing two deprotonated ligands, [L]^2–, two dimethylformamide (dmf) molecules and two UO₂²⁺ centers. Three C–H···O type hydrogen bonds involving one uranyl oxygen, two dmf hydrogens, and the imine hydrogen link the dinuclear units into a two‐dimensional network. Compound 2 is a cocrystal of two mononuclear units, [(UO₂)(L²)(H₂O)⊂(H₂O)] (unit 1) and [(UO₂)(L²)(H₂O)] (unit 2). In unit 1, the non‐coordinated water molecule forms hydrogen bonds with oxygens of phenoxo, ethoxy, and coordinated water molecules resulting in the formation of an inclusion product. The overall supramolecular structure of compound 2 is one‐dimensional and consists of interlinked self‐assembled dimeric unit of unit 1 and unit 2. Cyclic voltammetric measurements reveal that the uranium(VI) center in [(UO₂)₂(L¹)₂(dimethylformamide)₂] ( 1 ) is reduced quasireversibly at E_1/2 = –773 mV with ΔE_P = 121 mV, while the metal center in [(UO₂)(L²)(H₂O)⊂(H₂O)]·[(UO₂)(L²)(H₂O)] ( 2 ) is reduced reversibly with E_1/2 = –765 mV with ΔE_P = 68 mV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)