Reactions of cyclohexenyl halides with tributylstannane. Stereoelectronic effects on SH2 reactions at halogen

1983 ◽  
Vol 36 (11) ◽  
pp. 2123 ◽  
Author(s):  
ALJ Beckwith ◽  
SW Westwood
Keyword(s):  
Halogen Atom ◽  
Halogen Bonds ◽  
Stereoelectronic Effects ◽  
Catalysed Reaction ◽  
Homolytic Fission ◽  
Bromo Compound

Allylic halogenation of t-butylcyclohexene (2a) with t-butyl hypochlorite or N-bromosuccinimide affords mixtures containing mainly trans-5-t-butyl-3-chlorocyclohexene (2b) and the corresponding trans bromo compound (2c) respectively. The copper-catalysed reaction of (2a) with t-butyl perbenzoate shows similar but less pronounced stereoselectivity. Halogen-atom abstraction by tributyltin radicals, generated from tributylstannane, proceeds more rapidly from the trans halides (2b) and (2c) than from their cis epimers (3b) and (3c). These results suggest that homolytic fission or formation of allylic C-halogen bonds is sensitive to stereoelectronic effects.

scholarly journals Halogen-bonded adduct of 1,2-dibromo-1,1,2,2-tetrafluoroethane and 1,4-diazabicyclo[2.2.2]octane

2015 ◽  
Vol 71 (10) ◽  
pp. 900-902 ◽  
Author(s):  
Alan K. Brisdon ◽  
Abeer M. T. Muneer ◽  
Robin G. Pritchard
Keyword(s):  
Intermolecular Interaction ◽  
Halogen Atom ◽  
Halogen Bonding ◽  
Vapour Phase ◽  
Noncovalent Interaction ◽  
Lewis Base ◽  
Halogen Bonds ◽  
One Dimensional ◽  
Bonding Systems ◽  
Van Der Waals Radii

Halogen bonding is an intermolecular interaction capable of being used to direct extended structures. Typical halogen-bonding systems involve a noncovalent interaction between a Lewis base, such as an amine, as an acceptor and a halogen atom of a halofluorocarbon as a donor. Vapour-phase diffusion of 1,4-diazabicyclo[2.2.2]octane (DABCO) with 1,2-dibromotetrafluoroethane results in crystals of the 1:1 adduct, C2Br2F4·C6H12N2, which crystallizes as an infinite one-dimensional polymeric structure linked by intermolecular N...Br halogen bonds [2.829 (3) Å], which are 0.57 Å shorter than the sum of the van der Waals radii.

scholarly journals Halogen…π Interactions in the Complexes of Fluorenonophane With Haloforms

2021 ◽  
Author(s):  
Svitlana V. Shishkina ◽  
Viktoriya V. Dyakonenko ◽  
Oleg V. Shishkin ◽  
Volodimir P. Semynozhenko ◽  
Tatiana Yu. Bogashchenko ◽  
...  
Keyword(s):  
Halogen Atom ◽  
Halogen Bond ◽  
Bromine Atom ◽  
Quantum Chemical Study ◽  
Halogen Bonding ◽  
Chemical Study ◽  
Interaction Energies ◽  
Halogen Bonds ◽  
Guest Molecules ◽  
True Energy

Abstract The study of two complexes of fluorenonophane with CHCl3 and CHBr3 molecules has revealed that they differ mainly by the halogen bonds between host and guest molecules. The experimental and theoretical quantum chemical study has shown that the strength of a halogen bond depends on the nature of a halogen atom as well as its orientation to the π-system. The more positive electrostatic potential was revealed at the bromine atom indicating the stronger halogen bond with its participation that was confirmed by the interaction energies calculated for corresponding dimers and the evaluation of the true energy of a halogen bond. The orientation of the chlorine atom at the carbon aromatic atom instead of the center of the benzene ring leads to the shortest Hal…C distance that points out the stronger interaction according to the geometrical characteristics. The EDA analysis of the fluorenonophane complexes with CHCl3 and CHBr3 and their analogs with one halogen atom replaced by the hydrogen atom allows us to presume that the nature of halogen bonding is rather dispersive than electrostatic.

scholarly journals Halogen bonds involved in binding of halogenated ligands by protein kinases.

2016 ◽  
Vol 63 (2) ◽  
Author(s):  
Jarosław Poznański ◽  
Maria Winiewska ◽  
Honorata Czapinska ◽  
Anna Poznańska ◽  
David Shugar
Keyword(s):  
Hydrogen Bonds ◽  
Halogen Atom ◽  
Hinge Region ◽  
Geometrical Parameters ◽  
Halogen Bonds ◽  
Hydrogen Bond Donor ◽  
Peptide Bonds ◽  
Ligand Selectivity ◽  
Π Interactions ◽  
Protein X

Analysis of 664 known structures of protein kinase complexes with halogenated ligands revealed 424 short contacts between a halogen atom and a potential protein X-bond acceptor, the topology and geometry of which were analyzed according to the type of a halogen atom (X = Cl, Br, I) and a putative protein X-bond acceptor. Among 236 identified halogen bonds, the most represented ones are directed to backbone carbonyls of the hinge region and may replace the pattern of ATP-like hydrogen bonds. Some halogen-π interactions with either aromatic residues or peptide bonds, that accompany the interaction with the hinge region, may possibly enhance ligand selectivity. Interestingly, many of these halogen-π interactions are bifurcated. Geometrical preferences identify iodine as the strongest X-bond donor, less so bromine, while virtually no such preferences were observed for chlorine; and a backbone carbonyl as the strongest X-bond acceptor. The presence of a halogen atom in a ligand additionally affects the properties of proximal hydrogen bonds, which according to geometrical parameters get strengthened, when a nitrogen of a halogenated ligand acts as the hydrogen bond donor.

Reductive Dehalogenation of Environmental Contaminants: A Critical Review

1989 ◽  
Vol 24 (2) ◽  
pp. 299-322 ◽  
Author(s):  
R. M. Baxter
Keyword(s):  
Hydrogen Atom ◽  
Aromatic Compounds ◽  
Reductive Dechlorination ◽  
Halogen Atom ◽  
Environmental Contaminants ◽  
Methanogenic Bacteria ◽  
Photochemical Reactions ◽  
Reductive Dehalogenation ◽  
Iron Porphyrins ◽  
Aliphatic Compounds

Abstract It is generally recognized that reductive processes are more important than oxidative ones in transforming, degrading and mineralizing many environmental contaminants. One process of particular importance is reductive dehalogenation, i.e., the replacement of a halogen atom (most commonly a chlorine atom) by a hydrogen atom. A number of different mechanisms are involved in these reactions. Photochemical reactions probably play a role in some instances. Aliphatic compounds such as chloroethanes, partly aliphatic compounds such as DDT, and alicyclic compounds such as hexachlorocyclohexane are readily dechlorinated in the laboratory by reaction with reduced iron porphyrins such as hematin. Many of these are also dechlorinated by cultures of certain microorganisms, probably by the same mechanism. Such compounds, with a few exceptions, have been found to undergo reductive dechlorination in the environment. Aromatic compounds such as halobenzenes, halophenols and halobenzoic acids appear not to react with reduced iron porphyrins. Some of these however undergo reductive dechlorination both in the environment and in the laboratory. The reaction is generally associated with methanogenic bacteria. There is evidence for the existence of a number of different dechlorinating enzymes specific for different isomers. Recently it has been found that many components of polychlorinated biphenyls (PCBs), long considered to be virtually totally resistant to environmental degradation, may be reductively dechlorinated both in the laboratory and in nature. These findings suggest that many environmental contaminants may prove to be less persistent than was previously feared.

Abrupt spin crossover in iron(iii) complexes with aromatic anions

2019 ◽  
Vol 48 (41) ◽  
pp. 15515-15520 ◽  
Author(s):  
Sharon E. Lazaro ◽  
Adil Alkaş ◽  
Seok J. Lee ◽  
Shane G. Telfer ◽  
Keith S. Murray ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Spin Crossover ◽  
Spin Transition ◽  
Halogen Bonds ◽  
Aromatic Anions

Two iron(iii) complexes, [Fe(qsal-X)2]OTs·nH2O, are found to exhibit abrupt spin crossover with the spin transition temperature substituent dependent, and X⋯O halogen bonds linking the spin centres.

scholarly journals Convenient Access to Functionalized Non-Symmetrical Atropisomeric 4,4′-Bipyridines

Compounds ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 58-74
Author(s):  
Emmanuel Aubert ◽  
Emmanuel Wenger ◽  
Paola Peluso ◽  
Victor Mamane
Keyword(s):  
Solid State ◽  
Intermolecular Interactions ◽  
Medicinal Chemistry ◽  
Crystal Packing ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Halogen Bonds ◽  
Cross Coupling Reactions ◽  
Cyano Groups ◽  
Post Functionalization

Non-symmetrical chiral 4,4′-bipyridines have recently found interest in organocatalysis and medicinal chemistry. In this regard, the development of efficient methods for their synthesis is highly desirable. Herein, a series of non-symmetrical atropisomeric polyhalogenated 4,4′-bipyridines were prepared and further functionalized by using cross-coupling reactions. The desymmetrization step is based on the N-oxidation of one of the two pyridine rings of the 4,4′-bipyridine skeleton. The main advantage of this methodology is the possible post-functionalization of the pyridine N-oxide, allowing selective introduction of chlorine, bromine or cyano groups in 2- and 2′-postions of the chiral atropisomeric 4,4′-bipyridines. The crystal packing in the solid state of some newly prepared derivatives was analyzed and revealed the importance of halogen bonds in intermolecular interactions.

Controlling the molecular arrangement of racemates through weak interactions: the synergy between π-interactions and halogen bonds

2021 ◽  
Author(s):  
Carlos Romero-Nieto ◽  
A. de Cózar ◽  
Elzbieta Regulska ◽  
John B. Mullenix ◽  
Frank Rominger ◽  
...  
Keyword(s):  
Weak Interactions ◽  
Halogen Bonds ◽  
Π Interactions ◽  
Molecular Arrangement ◽  
Π Stacking

The combination of halogend bonds from PO and N-moieties with π-stacking leads to sort out R- and S-isomers into homoleptic, porous assemblies.

Sign in / Sign up

Export Citation Format

Share Document