scholarly journals Determination of Hammett Sigma Constants by Intramolecular Hydrogen Bonding

Nature ◽  
1958 ◽  
Vol 182 (4645) ◽  
pp. 1299-1299 ◽  
Author(s):  
A. T. SHULGIN ◽  
A. W. BAKER
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen

Synthesis of 2', 6'-Dihydroxychalcones by Using Tetrahydropyran-2-yl and Trialkylsilyl Protective Groups; the Crystal Structure Determination of 2',6'-Dihydroxy-2,4,6-trimethoxychalcone

1989 ◽  
Vol 42 (7) ◽  
pp. 1103 ◽  
Author(s):  
CO Miles ◽  
L Main ◽  
BK Nicholson
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Silyl Ether ◽  
X Ray ◽  
Protective Groups ◽  
Intramolecular Hydrogen ◽  
First Time ◽  
Mild Acid

Two improved general routes to 2′,6′-dihydroxychalcones are described in which the final step is protective-group removal from O 2′ under mild acid conditions. The first involves base-catalysed condensation of benzaldehydes with 2′-hydroxy-6′-tetrahydropyran-2-yloxyacetophenone, the second ring-opening of 5-hydroxyflavanones with 1,8-diazabicyclo[5.4.0]undec-7-ene in the presence of a trialkylchlorosilane to trap out the chalcone as a bis silyl ether. Chalcones prepared by the first route are 2',6'-dihydroxychalcone (1), and its 4-methoxy (2), 3,4-dimethoxy (3), 3,4,5-trimethoxy (4), and 2,4,6-trimethoxy (5) derivatives. The 4-chloro derivative (6) and the chalcone from hesperetin are prepared by the second method. .The X-ray crystal structure of 2',6'-dihydroxy-2,4,6-trimethoxychalcone (5), the first for a 2',6′-dihydroxychalcone, is reported, the hydrogen involved in intramolecular hydrogen-bonding between the carbonyl and phenolic oxygens being located for the first time for any 2'-hydroxychalcone derivative. The O 6' involved in the intramolecular hydrogen-bonding is also hydrogen-bonded intermolecularly to the hydrogen of the other (2'-)hydroxy group of a neighbouring molecule in the lattice. 13C n.m.r. data are the first reported for a series of 2',6'-dihydroxychalcones.

Photochemical isomerization of 7-aryl-substituted 1H-Azepin-2(3H)-ones. Formation and X-ray structure determination of atropisomeric ketimines

1983 ◽  
Vol 36 (10) ◽  
pp. 2073 ◽  
Author(s):  
H Becker ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Hydrogen Bonding ◽  
Structure Determination ◽  
Intramolecular Hydrogen Bonding ◽  
Phenolic Hydroxyl ◽  
X Ray Diffraction ◽  
X Ray ◽  
Photochemical Isomerization ◽  
Intramolecular Hydrogen

The structures of two isomeric 3,5-di-t-butyl-2-[(3,5-di-t-butyl-2-hydroxyphenyl){(Z)-methylimino}- methyl]cyclopent-2-en-1-ones, formed upon photoexcitation of 3,5-di-t-butyl-7-(3,5-di-t-butyl-2- hydroxyphenyl)-1-methyl-1H-azepin-2(3H)-one in methanol, have been established by X-ray diffraction, and are found to be examples of atropisomeric ketimines. In both isomers, the geometry of imino substitution is characterized by intramolecular hydrogen bonding with the phenolic hydroxyl.

Einfluß der Enolisierung auf die Reduktion von β Ketocarbonsäure-Derivaten mit Zinkborhydrid / Influence of the Enol Formation on the Reduction of β-Keto Carboxylic Acid Derivatives by Zinc Borohydride

1991 ◽  
Vol 46 (12) ◽  
pp. 1713-1719 ◽  
Author(s):  
Herbert Meier ◽  
Volker Krause
Keyword(s):  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Structure Determination ◽  
Intramolecular Hydrogen Bonding ◽  
Steric Effects ◽  
Group A ◽  
Hydroxy Compounds ◽  
Intramolecular Hydrogen ◽  
Enol Formation

Depending on the keto-enol equilibrium 1 ⇄ 2 reduction of the esters and the amides 1/2 a—g with Zn(BH4)2/ZnCl2 attacks either at the CO or at the CO2R group. A high diastereoselectivity (98:2 or more) is observed for the formation of the β-hydroxy compounds 3a,b,c,e,f in favour of the erythro forms. As to the structure determination of 3, different steric effects and different intramolecular hydrogen bonding have to be considered, leading to different rotameric populations.

Theoretical study of intramolecular hydrogen bonding and molecular geometry of 2-trifluoromethylphenol

10.1002/jcc.2 ◽  
1996 ◽  
Vol 17 (16) ◽  
pp. 1804-1819 ◽  
Author(s):  
Attila Kov�cs ◽  
Istv�n Kolossv�ry ◽  
G�bor I. Csonka ◽  
Istv�n Hargittai
Keyword(s):  
Hydrogen Bonding ◽  
Theoretical Study ◽  
Molecular Geometry ◽  
Intramolecular Hydrogen Bonding ◽  
Intramolecular Hydrogen
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