Diastereoselectivity in asymmetric allylations: The role of vicinal chirality in the allyl nucleophile for SE2′ reactions with aldehydes

2004 ◽  
Vol 82 (2) ◽  
pp. 120-130 ◽  
Author(s):  
David R Williams ◽  
Kevin G Meyer ◽  
Khalida Shamim ◽  
Samarjit Patnaik
Keyword(s):  
Chiral Auxiliary ◽  
Asymmetric Allylation ◽  
Relative Significance ◽  
Homoallylic Alcohols ◽  
In Situ Formation

A series of nonracemic homoallylic alcohols have been prepared by asymmetric allylation using the (R,R)- and (S,S)-1,2-diamino-1,2-diphenylethane bis-sulfonamide controller ligands for in situ formation of chiral B-allyl-1,3,2-diazaborolidines. Diastereofacial selectivity is influenced by adjacent stereochemistry incorporated into the allyl moiety at C-2, in addition to the expected role of the chiral auxiliary. Additional asymmetry in the aldehyde reactant introduces threefold stereodifferentiation. A model is developed to identify reinforcing stereochemical relationships, and examples have ascertained the relative significance of these factors. The methodology supports the construction of complex homoallylic alcohols in a highly convergent fashion.Key words: asymmetric allylation, diastereofacial selectivity, 1,4-stereocontrol, homoallylic alcohols.

The pivotal role of oxygen in establishing superlow friction by inducing the in situ formation of a robust MoS2 transfer film

2021 ◽  
Vol 594 ◽  
pp. 824-835
Author(s):  
Guomin Yu ◽  
Qingyi Qian ◽  
Donghao Li ◽  
Zhenxi Zhang ◽  
Kexin Ren ◽  
...  
Keyword(s):  
Transfer Film ◽  
Pivotal Role ◽  
In Situ Formation

Role of grafted chains for the in situ formation of Ag nanoparticles within poly(epichlorohydrin)-g-polymethacrylate films

2009 ◽  
Vol 9 (4) ◽  
pp. e298-e300
Author(s):  
Jung Tae Park ◽  
Kyung Ju Lee ◽  
Jong Kwan Koh ◽  
Jong Hak Kim ◽  
Ki Bong Lee
Keyword(s):  
Ag Nanoparticles ◽  
In Situ Formation

scholarly journals Planetesimal fragmentation and giant planet formation: the role of planet migration

2014 ◽  
Vol 9 (S310) ◽  
pp. 204-207
Author(s):  
O. M. Guilera ◽  
D. Swoboda ◽  
Y. Alibert ◽  
G. C. de Elía ◽  
P. J. Santamaría ◽  
...  
Keyword(s):  
Giant Planet ◽  
Giant Planets ◽  
New Work ◽  
The Standard Model ◽  
Planet Migration ◽  
In Situ Formation ◽  
Core Accretion ◽  
Planet Accretion

AbstractIn the standard model of core accretion, the cores of the giant planets form by the accretion of planetesimals. In this scenario, the evolution of the planetesimal population plays an important role in the formation of massive cores. Recently, we studied the role of planetesimal fragmentation in the in situ formation of a giant planet. However, the exchange of angular momentum between the planet and the gaseous disk causes the migration of the planet in the disk. In this new work, we incorporate the migration of the planet and study the role of planet migration in the formation of a massive core when the population of planetesimals evolves by planet accretion, migration, and fragmentation.

{10-12} Twinning Mechanism During In Situ Micro-Tensile Loading of Pure Mg: Role of Basal Slip and Twin-Twin Boundary Interaction

2020 ◽  
Author(s):  
Nicolò Maria della Ventura ◽  
Szilvia Kalácska ◽  
Daniele Casari ◽  
Thomas Edward James Edwards ◽  
Johann Michler ◽  
...  
Keyword(s):  
Twin Boundary ◽  
Basal Slip ◽  
Tensile Loading ◽  
Boundary Interaction

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

Indium Bromide-catalyzed Unprecedented Hydrogenolysis: A Novel One-Pot Synthesis of Per-O-Acetylated β-carboxymethyl O and S-glycosides

2020 ◽  
Vol 24 (8) ◽  
pp. 900-908
Author(s):  
Ram Naresh Yadav ◽  
Amrendra K Singh ◽  
Bimal Banik
Keyword(s):  
Asymmetric Synthesis ◽  
Chiral Auxiliary ◽  
Bioactive Molecules ◽  
One Pot ◽  
Enantiomerically Pure ◽  
Stereoselective Glycosylation ◽  
One Pot Synthesis ◽  
Wide Range

Numerous O (oxa)- and S (thia)-glycosyl esters and their analogous glycosyl acids have been accomplished through stereoselective glycosylation of various peracetylated bromo sugar with benzyl glycolate using InBr3 as a glycosyl promotor followed by in situ hydrogenolysis of resulting glycosyl ester. A tandem glycosylating and hydrogenolytic activity of InBr3 has been successfully investigated in a one-pot procedure. The resulting synthetically valuable and virtually unexplored class of β-CMGL (glycosyl acids) could serve as an excellent potential chiral auxiliary in the asymmetric synthesis of a wide range of enantiomerically pure medicinally prevalent β-lactams and other bioactive molecules of diverse medicinal interest.

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