Very high 1,2-asymmetric induction in the reaction of allyl-9-BBN with certain imines. Evidence for a stereoelectronic effect to enhance the Cram selectivity

1984 ◽  
Vol 106 (17) ◽  
pp. 5031-5033 ◽  
Author(s):  
Yoshinori Yamamoto ◽  
Toshiaki Komatsu ◽  
Kazuhiro Maruyama
Keyword(s):  
Asymmetric Induction ◽  
Stereoelectronic Effect ◽  
Very High

Optisch aktive Übergangsmetall-Komplexe, LXIII [1] Asymmetrische Induktion in C5H5Mo(CO)2LX-Diastereomeren-Gleichgewichten / Optically Active Transition Metal Complexes, LXIII [1] Asymmetrie Induction in C5H5Mo(CO)2LX Diastereoisomer Equilibria

1979 ◽  
Vol 34 (10) ◽  
pp. 1418-1423 ◽  
Author(s):  
Henri Brunner ◽  
Isabella Bauer ◽  
Rainer Lukas
Keyword(s):  
Transition Metal Complexes ◽  
Nmr Spectra ◽  
Optically Active ◽  
Asymmetric Induction ◽  
Chiral Ligand ◽  
Phenyl Substituent ◽  
H Nmr ◽  
Weak Attraction ◽  
Active Transition ◽  
Very High

Abstract The thioamidato complexes C5H5(CO)2MoSC(R)NCH(CH3) (Ar), derived from acetic acid R = CH3 and benzoic acid R = C6H5, were prepared and characterized. The diastereo-isomers, differing in their 1H NMR spectra, were partly separated by fractional crystallization. After equilibration with respect to the labile Mo configuration the diastereoisomer ratio, a measure for the asymmetric induction from the chiral ligand on the formation of the two Mo configurations at equilibrium, was determined by 1H NMR integration. The asymmetric induction is very high for Ar = o-tolyl [76% (R = C6H3) and 84% (R = C6H5)] compared to Ar = phenyl [48% (R = CH3) and 56% (R = C6H5)] and Ar = m-and p-tolyl [52 and 44% (R = CH3)]. The (CO)3Cr complexed phenyl substituent with only 10% asymmetric induction does not show the β-phenyl effect, a weak attraction between aryl groups in β-position to the metal atom and the MC5H5 moiety.

scholarly journals Asymmetric catalytic addition of diorganozinc reagents to imines: Scope and application

2005 ◽  
Vol 77 (7) ◽  
pp. 1259-1267 ◽  
Author(s):  
André B. Charette ◽  
Alessandro A. Boezio ◽  
Alexandre Côté ◽  
Elaine Moreau ◽  
Julien Pytkowicz ◽  
...  
Keyword(s):  
Metal Complex ◽  
Asymmetric Induction ◽  
Asymmetric Catalytic ◽  
Catalytic Addition ◽  
High Degree ◽  
Very High

The copper-catalyzed diorganozinc addition to N-diphenylphosphinoylimines was shown to proceed with a very high degree of enantiocontrol if the reaction was run in the presence of Me-DuPHOS monoxide ligand (BozPHOS). The scope of the reaction is described as well as our efforts to identify the nature of the enantioactive metal complex responsible for the high asymmetric induction.

Very high 1,2- and 1,3-asymmetric induction in the reactions of allylic boron compounds with chiral imines

1986 ◽  
Vol 108 (24) ◽  
pp. 7778-7786 ◽  
Author(s):  
Yoshinori. Yamamoto ◽  
Kazuhiro. Maruyama ◽  
Toshiaki. Komatsu ◽  
Wataru. Ito
Keyword(s):  
Asymmetric Induction ◽  
Boron Compounds ◽  
Chiral Imines ◽  
Very High

ChemInform Abstract: Very High 1,2- and 1,3-Asymmetric Induction in the Reactions of Allylic Boron Compounds with Chiral Imines.

ChemInform ◽  
1987 ◽  
Vol 18 (16) ◽  
Author(s):  
Y. YAMAMOTO ◽  
S. NISHII ◽  
K. MARUYAMA ◽  
T. KOMATSU ◽  
W. ITO
Keyword(s):  
Asymmetric Induction ◽  
Boron Compounds ◽  
Chiral Imines ◽  
Very High

scholarly journals The mechanism of stereoselectivity in the cycloaddition reactions of α-hydroxy-ortho-quinodimethanes with the fumarate of methyl lactate and mandelate

1993 ◽  
Vol 71 (6) ◽  
pp. 827-833 ◽  
Author(s):  
James L. Charlton ◽  
Shawn Maddaford
Keyword(s):  
Hydrogen Bonding ◽  
Cycloaddition Reaction ◽  
Diels Alder ◽  
Asymmetric Induction ◽  
Cycloaddition Reactions ◽  
Methyl Lactate ◽  
Very High

The Diels–Alder cycloaddition reaction of the fumarate of methyl lactate or methyl mandelate with α-hydroxy-ortho-quinodimethane produces an unexpected exo product with very high asymmetric induction. Experiments and calculations have been carried out that show that the origin of the stereoselectivity in these reactions is related to hydrogen bonding between the α-hydroxy-o-quinodimethane and the lactate or mandelate group in the dienophile.

Very High Resolution Analysis of the Dynamics of a Coronal Plasmoid

1994 ◽  
Vol 144 ◽  
pp. 593-596
Author(s):  
O. Bouchard ◽  
S. Koutchmy ◽  
L. November ◽  
J.-C. Vial ◽  
J. B. Zirker
Keyword(s):  
High Resolution ◽  
Solar Eclipse ◽  
Total Solar Eclipse ◽  
Field Of View ◽  
Small Field ◽  
High Resolution Analysis ◽  
Ccd Observations ◽  
Resolution Analysis ◽  
Very High ◽  
Small Field Of View

AbstractWe present the results of the analysis of a movie taken over a small field of view in the intermediate corona at a spatial resolution of 0.5“, a temporal resolution of 1 s and a spectral passband of 7 nm. These CCD observations were made at the prime focus of the 3.6 m aperture CFHT telescope during the 1991 total solar eclipse.

Monte Carlo Algorithms for Moments of Transition Arrays

1988 ◽  
Vol 102 ◽  
pp. 79-81
Author(s):  
A. Goldberg ◽  
S.D. Bloom
Keyword(s):  
Monte Carlo ◽  
State Vector ◽  
Basis Vector ◽  
Collective State ◽  
Dispersion Characteristics ◽  
Dipole Strength ◽  
The Third ◽  
Monte Carlo Algorithms ◽  
Third Moment ◽  
Very High

AbstractClosed expressions for the first, second, and (in some cases) the third moment of atomic transition arrays now exist. Recently a method has been developed for getting to very high moments (up to the 12th and beyond) in cases where a “collective” state-vector (i.e. a state-vector containing the entire electric dipole strength) can be created from each eigenstate in the parent configuration. Both of these approaches give exact results. Herein we describe astatistical(or Monte Carlo) approach which requires onlyonerepresentative state-vector |RV> for the entire parent manifold to get estimates of transition moments of high order. The representation is achieved through the random amplitudes associated with each basis vector making up |RV>. This also gives rise to the dispersion characterizing the method, which has been applied to a system (in the M shell) with≈250,000 lines where we have calculated up to the 5th moment. It turns out that the dispersion in the moments decreases with the size of the manifold, making its application to very big systems statistically advantageous. A discussion of the method and these dispersion characteristics will be presented.

Decomposition of the metastable beta titanium alloy Ti-15-3

1983 ◽  
Vol 41 ◽  
pp. 264-265
Author(s):  
Y. L. Chen ◽  
S. Fujlshiro
Keyword(s):  
Low Cost ◽  
High Strength ◽  
Alpha Phase ◽  
Thick Sheet ◽  
Omega Phase ◽  
Beta Titanium Alloy ◽  
Beta Titanium ◽  
Beta Matrix ◽  
Metastable Beta ◽  
Very High

Metastable beta titanium alloys have been known to have numerous advantages such as cold formability, high strength, good fracture resistance, deep hardenability, and cost effectiveness. Very high strength is obtainable by precipitation of the hexagonal alpha phase in a bcc beta matrix in these alloys. Precipitation hardening in the metastable beta alloys may also result from the formation of transition phases such as omega phase. Ti-15-3 (Ti-15V- 3Cr-3Al-3Sn) has been developed recently by TIMET and USAF for low cost sheet metal applications. The purpose of the present study was to examine the aging characteristics in this alloy.The composition of the as-received material is: 14.7 V, 3.14 Cr, 3.05 Al, 2.26 Sn, and 0.145 Fe. The beta transus temperature as determined by optical metallographic method was about 770°C. Specimen coupons were prepared from a mill-annealed 1.2 mm thick sheet, and solution treated at 827°C for 2 hr in argon, then water quenched. Aging was also done in argon at temperatures ranging from 316 to 616°C for various times.

Deformation Replication

1970 ◽  
Vol 28 ◽  
pp. 280-281
Author(s):  
J. Temple Black
Keyword(s):  
Cutting Speed ◽  
Machining Process ◽  
Depth Of Cut ◽  
Rake Face ◽  
Orthogonal Machining ◽  
Aluminum Chips ◽  
Before And After ◽  
Materials Used ◽  
Glass Knife ◽  
Very High

Tool materials used in ultramicrotomy are glass, developed by Latta and Hartmann (1) and diamond, introduced by Fernandez-Moran (2). While diamonds produce more good sections per knife edge than glass, they are expensive; require careful mounting and handling; and are time consuming to clean before and after usage, purchase from vendors (3-6 months waiting time), and regrind. Glass offers an easily accessible, inexpensive material ($0.04 per knife) with very high compressive strength (3) that can be employed in microtomy of metals (4) as well as biological materials. When the orthogonal machining process is being studied, glass offers additional advantages. Sections of metal or plastic can be dried down on the rake face, coated with Au-Pd, and examined directly in the SEM with no additional handling (5). Figure 1 shows aluminum chips microtomed with a 75° glass knife at a cutting speed of 1 mm/sec with a depth of cut of 1000 Å lying on the rake face of the knife.

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