Determination of absolute configuration using vibrational circular dichroism spectroscopy: the chiral sulfoxide 1-(2-methylnaphthyl) methyl sulfoxide

We report the determination of the absolute configuration (AC) of the chiral sulfoxide, 1-(2-methylnaphthyl) methyl sulfoxide, 1, using vibrational circular dichroism (VCD) spectroscopy. The VCD of 1 has been measured in the mid-IR spectral region in CCl(4) solution. Analysis employs the ab initio DFT/GIAO methodology. DFT calculations predict two stable conformations of 1, E and Z, Z being lower in energy than E by <1 kcal/mol. In both conformations the S-O bond is rotated from coplanarity with the naphthyl moiety by 30-40 degrees. The predicted unpolarized absorption ("IR") spectrum of the equilibrium mixture of the two conformations permits assignment of the experimental IR spectrum in the mid-IR spectral region. The presence of both E and Z conformations is clearly evident. The VCD spectrum predicted for S-1 is in excellent agreement with the experimental spectrum of (-)-1, unambiguously defining the AC of 1 as R(+)/S(-).     

Evaluation of the assurance GDS for E. coli O157:H7 method and assurance GDS for shigatoxin genes method in selected foods: collaborative study

A multilaboratory collaborative study was conducted to compare the Assurance GDS for E. coli 0157:H7 method and the reference culture methods for the detection of E. coli 0157:H7 in orange juice, raw ground beef, and fresh lettuce. A separate companion assay, the Assurance GDS for Shigatoxin Genes method was also evaluated with the same test portions. Fifteen laboratories participated in the study. A Chi square analysis of each of the 3 food types at the high, low, and uninoculated control levels was performed. For all foods, the Assurance GDS for E. coli O157:H7 method and the Assurance GDS for Shigatoxin Genes method were equivalent to or better than the reference methods.     

A new and unusual isomerism in [Fe(CO)2 {P(OR)3}2 (SO2)] complexes (R = aryl)

[Fe(CO)₂ {P(OR)₃}₂ (SO₂)] complexes (R = aryl) exist in solution as equilibrium mixtures of two isomers; both have been shown by X-ray diffraction studies (where R = Ph or o-MeC₆H₄) to have planar coordination about SO₂ and trigonal bipyramidal coordination about Fe, but in one isomer (R = Ph) the equatorial plane is occupied by SO₂ and two CO ligands whilst in the other one (R = o-MeC₆H₄) it is occupied by the SO₂ and two P ligands.     

Application of P-stereogenic aminophosphine phosphinite ligands in asymmetric hydroformylation

New chiral aminophosphine phosphinite ligands with a stereogenic center at the aminophosphine phosphorus atom were prepared based on (R,S)-ephedrine as the chiral auxiliary and backbone. Substituents at the chiral aminophosphine as well as at the phosphinite phosphorus atom were varied. These new ligands were applied to the rhodium-catalyzed asymmetric hydroformylation of vinyl arenes. The enantiomeric excess reached up to 77%. 1H and 31P NMR studies of the Rh complexes under syngas pressure reveal that [HRh(CO)2(PP)] complexes with the NP* moiety in an axial position are responsible for enantioselectivity.     

Polyfluoro-compounds based on the cycloheptane ring system. Part 6. Bicyclic compounds derived from nonafluorocyclohepta-1, 3-dienes and from octafluorocyclohepta-1, 3, 5-triene

1H-, 2H-, and 5H- Nonafluoro- and 1H,4H-octafluoro-cyclohepta-1,3 diene afforded the corresponding H-substituted polyfluorobicyclo(3, 2, 0)- hept-6-enes by cross-ring bond formation between positions 1 and 4. Octafluorocyclohepta-1, 3, 5-triene similarly gave octafluorobicyclo- (3,2,0)hepta-2,6-diene. By passage over cobalt(III) fluoride at 100°C, the 1H-bicyclo-6-ene gave 1H-undecafluorobicyclo(3, 2, 0)heptane and thence the corresponding fluorocarbon. The bridgehead hydrogen of the 1H- bicyclo-ane was sufficiently acidic to exchange for deuterium with deuterium oxide, alone or containing some potassium hydroxide, but longer exposure to aqueous potash gave decafluorobicyclo(3, 2, 0)hept-1(5)-ene. This was oxidised by potassium permanganate in acetone to give decafluoro-1, 5- dihydroxy-8-oxabicyclo(3, 2, 1)octane (hydrated), which underwent methylation by diazomethane to the corresponding 1,5-dimethoxy-compound. A Diels-Alder reaction between ethylene and 1H-nonafluorocyclohepta-1, 3- diene afforded 1H,8H,8H,9H,9H-nonafluoro-bicyclo(3,2,2)non-6-ene. Cobalt (III) fluoride at 300°C converted this principally to 1H-pentadecafluoro- bicyclo(3,2,2)nonane. The bridgehead hydrogen of this was exchanged for deuterium using deuterium oxide alone or containing potassium hydroxide. However, dehydrofluorination occurred with bases, though an olefin could not be isolated.     

Identification of parameters by the distribution of the maximum random variable: The general multivariate normal case

Summary LetX ₁,X ₂, ...,X _r ber independentn-dimensional random vectors each with a non-singular normal distribution with zero means and positive partial correlations. Suppose thatX _i =(X _i1 , ...,X _in ) and the random vectorY=(Y ₁, ...,Y _n ), their maximum, is defined byY _j =max{X _ij :1ir}. LetW be another randomn-vector which is the maximum of another such family of independentn-vectorsZ ₁,Z ₂, ...,Z _s . It is then shown in this paper that the distributions of theZ _i 's are simply a rearrangement of those of theZ _j 's (and of course,r=s), whenever their maximaY andW have the same distribution. This problem was initially studied by Anderson and Ghurye [2] in the univariate and bivariate cases and motivated by a supply-demand problem in econometrics.