Diastereoselective formation of 2-aryl-3-arenesulfonyl 4-ethyl-1,3-oxazolidines: An X-ray crystallographic and H NMR study

N-Arylsulfonamides of (R)- and (S)-2-amino-1-butanol, on condensation with aromatic aldehydes produced diastereomerically pure 2-aryl-3-arenesulfonyl 4-ethyl-1,3-oxazolidines. The absolute configurations of one enantiomeric pair have been determined from two fully refined X-ray structures, supplemented by nmr data.     

Synthesis of skipped enynes via phosphine-promoted couplings of propargylcopper reagents

An electron-rich phosphine additive is critical and sufficient for propargyl-selective couplings of propargylcopper reagents and alkenyl halides. This method is complementary to those previously described, in which high allenyl selectivity is observed in analogous coupling reactions. While the basis of the phosphine effect requires further investigation, the information gained in these studies enables the synthesis of complex molecules by way of skipped enyne intermediates.     

Zweifach arsenverbrückte CrFe-, MoFe- und WFe-bindungen

The reaction of K₂Fe(CO)₄ with (CO)₄ M(AsMe₂Cl)₂ (M  Cr, Mo, W) gives low yields of the new heterodinuclear complexes (CO)₄M-[μ-AsMe₂]₂-Fe(CO)₃ with CrFe, MoFe and WFe bonds.     

Macrocyclization by Nickel‐Catalyzed,Ester‐Promoted,Epoxide–Alkyne Reductive Coupling: Total Synthesis of (−)‐Gloeosporone

Ringing the changes : The total synthesis of the title compound centers around a novel strategy that employs a nickel(0)–phosphine complex and triethyl borane in an efficient closure of a 14‐membered ring through C? C bond formation (see scheme; cod=cyclooctadiene). The synthesis was accomplished in 10 steps and in approximately 9 % overall yield.

     

Radical cation ester cleavage in solution: mechanism of the mesolytic O-CO bond scission

A wide range of enol carbonate, carbamate, and ester radical cations is characterized in solution by cyclic voltammetry and EPR spectroscopy. Preparative transformations using one-electron oxidants or anodic oxidation yield benzofurans after O-CO bond cleavage. Mechanistic investigations and direct detection of radical intermediates reveal that all enol radical cations undergo exclusively O-CO bond cleavage to provide alpha-carbonyl cations and acyl (or alternatively, alkoxyacyl and aminoacyl) radicals, respectively. The kinetics of the mesolytic fragmentation and the influence of nucleophilic additives have been determined using fast-scan cyclic voltammetry.