Stable carbocations. 273. [1.1.1.1]- and [2.2.1.1]Pagodane dications: frozen two-electron Woodward-Hoffmann transition-state models

1988 ◽  
Vol 110 (23) ◽  
pp. 7764-7772 ◽  
Author(s):  
G. K. Surya. Prakash ◽  
V. V. Krishnamurthy ◽  
Rainer. Herges ◽  
Robert. Bau ◽  
Hanna. Yuan ◽  
...  
Keyword(s):  
Transition State ◽  
State Models

Model calculations of isotope effects. VII. Deprotonation of 2-nitropropane by oxy anion bases

1983 ◽  
Vol 36 (8) ◽  
pp. 1503
Author(s):  
DJ McLennan
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Isotope Effects ◽  
Experimental Results ◽  
Electron Delocalization ◽  
Model Calculations ◽  
Charge Delocalization ◽  
Successful Model ◽  
Deuterium Isotope Effects ◽  
State Models

Model calculations of primary and secondary deuterium isotope effects for the hydroxide-induced deprotonation of 2-nitropropane are reported. Various transition-state models have been examined in an effort to reproduce experimental results. A purely pyramidal transition state in which proton transfer has run far ahead of carbon rehybridization and charge delocalization is a successful model as far as isotope effects are concerned, but may fail on other counts. Three incipient trigonal models for the transition state have been tested, and, although none can be firmly eliminated by the resultant isotope effects, those involving the proton transfer's running ahead of electron delocalization and perhaps carbon rehybridization are favoured.

γ-Silylated α,β-unsaturated amides — Preparation by [1,5]-sigmatropic rearrangement and use as masked dienolate equivalents in carbonyl condensations

2009 ◽  
Vol 87 (6) ◽  
pp. 745-759 ◽  
Author(s):  
James R. Green ◽  
Babajide I. Alo ◽  
Marek Majewski ◽  
Victor Snieckus
Keyword(s):  
Oxygen Atom ◽  
Transition State ◽  
Condensation Product ◽  
Aromatic Aldehydes ◽  
Sigmatropic Rearrangement ◽  
Fluoride Ion ◽  
Bidentate Coordination ◽  
State Models

The reaction of lithium dienolates derived from N,N-dialkylsenecioamides (1a–1c) with triorganosilyl electrophiles occurs initially at the oxygen atom predominantly, and is followed by an O → C silicon migration to afford the γ-silylated senecioamides (4a–4h). The γ-silylated senecioamide Z-4a undergoes fluoride-ion-mediated condensations with aromatic aldehydes to give kinetic α-(6) and thermodynamic γ-(5) condensation product patterns comparable to lithium dienolates. The TiCl4-mediated reactions with aldehydes gives α-products (6) in a highly syn-selective manner. Possible transition-state models for the syn-selective condensations are discussed and a chair-like transition state featuring bidentate coordination to titanium (11) is proposed.

Rational vs Random Parameters in Transition State Modeling: MM2 Transition State Models for Intramolecular Hydride Transfers

1994 ◽  
Vol 116 (22) ◽  
pp. 9943-9946 ◽  
Author(s):  
Kirsten P. Eurenius ◽  
K. N. Houk
Keyword(s):  
Transition State ◽  
Random Parameters ◽  
State Models

ChemInform Abstract: New Transition-State Models and Kinetics of Elimination Reactions of Tertiary Alcohols over Aluminum Oxide.

ChemInform ◽  
2010 ◽  
Vol 30 (12) ◽  
pp. no-no
Author(s):  
H. A. Dabbagh ◽  
J. Mohammad Salehi
Keyword(s):  
Aluminum Oxide ◽  
Transition State ◽  
Tertiary Alcohols ◽  
Elimination Reactions ◽  
State Models ◽  
Kinetics Of

Transition-state models are useful for versatile biocatalysts: kinetics and thermodynamics of enantioselective acylations of secondary alcohols catalyzed by lipase and subtilisin

2003 ◽  
Vol 22 (3-4) ◽  
pp. 181-192 ◽  
Author(s):  
Tadashi Ema ◽  
Kunihiro Yamaguchi ◽  
Yuji Wakasa ◽  
Akinori Yabe ◽  
Ryoichi Okada ◽  
...  
Keyword(s):  
Transition State ◽  
Secondary Alcohols ◽  
Kinetics And Thermodynamics ◽  
State Models
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