Steven F. Pedersen

Chiral recognition in the gas phase: mass spectrometric studies of diastereomeric cobalt complexes

Results of mass analyzed ion kinetic energy (MIKE) spectra and kinetic energy release (KER) measurements of diastereomeric octahedral cobalt complexes indicate that these diastereomers can be distinguished in the gas phase. Four alkyl tartrate esters were complexed to cobalt trisacetylacetonate (Co(acac)3) in the presence of a chiral auxiliary, RR- and SS-threohydrobenzoin. Different KER values of the product ion generated from [Co(acac)2/D- or L-diisopropyl tartrate]+ reflect differences in the precursor ion structure. The dissociation pathway resulting in this product ion is believed to arise via a hydride transfer from the acetylacetonate ligand to the metal center with subsequent loss of neutral organic species. It has been established that two conditions are necessary for observation of chiral recognition in this system; (1) the cobalt complex must be octahedral and (2) a chemical kinetic resolving agent must be present during formation of the complex.

Intermolecular pinacol cross coupling of aryl aldehydes or their dimethyl acetals with non-aryl aldehydes

Abstract 1-Aryl-2-alkyl-1,2-ethanediols have been synthesized via intermolecular pinacol cross coupling of aryl with non-aryl aldehydes. Dimethyl acetals of aryl aldehydes can also be cross coupled with non aryl aldehydes to yield 2-aryl-2-methoxy-1-alkyl-1-ethanols. The reaction is accomplished employing the vanadium(II) reagent [V2Cl3(THF)6]2[Zn2Cl6] which is prepared in situ from VCl3(THF)3.

Practical hydroxymethylation of aldehydes and ketones via pinacol cross-coupling reactions with paraformaldehyde

Abstract A general and practical method for the direct hydroxymethylation of aldehydes and ketones via pinacol cross-coupling with paraformaldehyde is described. The reaction is promoted by vanadium(II) ions which are conveniently generated from the reduction of VCl 3 (THF) 3 with zinc dust. Excellent yields of terminal diols are obtained and stereoselective coupling is observed with some chiral aldehydes and ketones.

Formation of a tetrahedral WC3 framework from a cyclic WC3(tungstenacyclobutadiene) system via attack on tungsten by nitrogen-doner ligands: X-ray study of W[C3Me2(But)][Me2N(CH2)2NMe2]Cl3

The tungstenacyclobutadiene complex W[C3Me2(But)]Cl3 reacts with Me2N(CH2)2 NMe2 to form the 1:1 adduct W[C3Me2(But)][Me2N(CH2)2 NMe2]Cl3; a single-crystal X-ray diffraction study of this product shows it to possess a ‘tungstenatetrahedrane’-like core with short W–C distances[2.040(7),2.115(7), 2.133(7)A].