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出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2013/09/20 09:44:36」(JST)
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In organic chemistry, a pericyclic reaction is a type of organic reaction wherein the transition state of the molecule has a cyclic geometry, and the reaction progresses in a concerted fashion. Pericyclic reactions are usually rearrangement reactions. The major classes of pericyclic reactions are:
Name |
Bond changes |
Sigma |
Pi |
Electrocyclic reaction |
+ 1 |
-1 |
Cycloaddition |
+2 |
-2 |
Sigmatropic reaction |
0 |
0 |
Group transfer reaction |
+ 1 |
-1 |
Cheletropic reaction |
+ 2 |
- 2 |
Dyotropic reaction |
0 |
0 |
In general, these are considered to be equilibrium processes, although it is possible to push the reaction in one direction by designing a reaction by which the product is at a significantly lower energy level; this is due to a unimolecular interpretation of Le Chatelier's principle. Pericyclic reactions often have related stepwise radical processes associated with them. Some pericyclic reactions, such as the [2+2] cycloaddition, are 'controversial' because their mechanism is not definitively known to be concerted (or may depend on the reactive system). Pericyclic reactions also often have metal-catalyzed analogs, although usually these are also not technically pericyclic, since they proceed via metal-stabilized intermediates, and therefore are not concerted.
A large photoinduced hydrogen sigmatropic shift was utilized in a corrin synthesis performed by Albert Eschenmoser containing a 16π system.[1]
Due to the principle of microscopic reversibility, there is a parallel set of "retro" pericyclic reactions, which perform the reverse reaction.
Contents
- 1 Pericyclic reactions in stereochemistry
- 2 Pericyclic reactions in biochemistry
- 3 See also
- 4 References
Pericyclic reactions in stereochemistry[edit source | edit]
It is well established that the diene can only inter in a cycloaddition reaction with a dienophile in the cisoid form and the rate of the reaction with the open chain dienes depends on the equilibrium proportions of the cisoid/transoid conformers. Thus substituents in the diene can significantly affect the rate of the reaction not only by their electronic character but by their influence on the conformers proportions.
Thus for example cis I -substituted butadiene I is less reactive than its trans isomer II since a bulky R disfavors the cisoid conformation. Bulky 2-substituents in the diene favor the cisoid conformation more than the transoid and thus the diene in this case is more reactive. [2]
Pericyclic reactions in biochemistry[edit source | edit]
Pericyclic reactions also occur in several biological processes.
- Claisen rearrangement of chorismate to prephenate in almost all prototrophic organisms.
- [1,5]-sigmatropic shift in the transformation of precorrin-8x to hydrogenobyrinic acid
- non-enzymatic, photochemical electrocyclic ring opening and a (1,7) sigmatropic hydride shift in vitamin D synthesis.
- a conversion of Isochorismate into salicylate and Pyruvate in a catalyzed, true pericyclic reaction.[3][4]
See also[edit source | edit]
References[edit source | edit]
- ^ A New Type of Corrin Synthesis. Yasuji Yamada, D. Miljkovic, P. Wehrli, B. Golding, P. Loliger, R. Keese, K. Miiller, and A. Eschenmoser. Angew. Chem. Int. Edit. 1969, 8(5),343-348.
- ^ An Introduction to Orbital Symmetry and Pericyclic Ractions 2006 - Prof. Dr. Fathy Mohamed Abdelrazek
- ^ Isochorismate Pyruvate Lyase: A Pericyclic Reaction Mechanism? Michael S. DeClue, Kim K. Baldridge, Dominik E. Künzler, Peter Kast, and Donald Hilvert J. Am. Chem. Soc.; 2005; 127(43) pp 15002 - 15003; (Communication) doi:10.1021/ja055871t Abstract
- ^ In this experiment isochorismate is deuterated in one specific position and subjected to the lyase. Two key observations rule out other reaction mechanisms, ionic or base promoted. From the kinetic isotope effect (value 2.34) it can be inferred that carbon to hydrogen bond breaking occurs in the transition state of the rate determining step. NMR spectroscopy shows that the deuterium atom is transferred exclusively to the pyruvate molecule.
English Journal
- Re-investigation of the fragmentation of protonated carotenoids by electrospray ionization and nanospray tandem mass spectrometry.
- Neto FC1, Guaratini T1,2, Costa-Lotufo L3, Colepicolo P4, Gates PJ5, Lopes NP1.
- Rapid communications in mass spectrometry : RCM.Rapid Commun Mass Spectrom.2016 Jul 15;30(13):1540-8. doi: 10.1002/rcm.7589.
- RATIONALE: Carotenoids are polyene isoprenoids with an important role in photosynthesis and photoprotection. Their characterization in biological matrices is a crucial subject for biochemical research. In this work we report the full fragmentation of 16 polyenes (carotenes and xanthophylls) by elect
- PMID 27321841
- Interplay between aromaticity and strain in double group transfer reactions to 1,2-benzyne.
- Fernández I1, Cossío FP2,3.
- Journal of computational chemistry.J Comput Chem.2016 May 30;37(14):1265-73. doi: 10.1002/jcc.24317. Epub 2016 Feb 11.
- Density Functional Theory calculations are used to explore the double hydrogen atom transfer from different alkanes to 1,2-benzyne. State-of-the-art calculations including the Activation Strain Model of reactivity, Energy Decomposition Analysis, and Valence Bond methods, reveal the origins of the re
- PMID 26864872
- The Catalytic Mechanism of a Natural Diels-Alderase Revealed in Molecular Detail.
- Byrne MJ1,2, Lees NR3, Han LC2,3, van der Kamp MW1,2,3, Mulholland AJ2,3, Stach JE4,5, Willis CL2,3, Race PR1,2.
- Journal of the American Chemical Society.J Am Chem Soc.2016 May 18;138(19):6095-8. doi: 10.1021/jacs.6b00232. Epub 2016 May 6.
- The Diels-Alder reaction, a [4 + 2] cycloaddition of a conjugated diene to a dienophile, is one of the most powerful reactions in synthetic chemistry. Biocatalysts capable of unlocking new and efficient Diels-Alder reactions would have major impact. Here we present a molecular-level description of t
- PMID 27140661
Japanese Journal
- DABCO触媒下におけるCyclopentadienoneと Alkynyl alkyl ketone類との環化反応
- Design, Generation, and Characterization of a 1,5-Hexadiene Bearing Two Lophyl Radicals as a Probe of the Stepwise Mechanism for the Cope Rearrangement
Related Links
- pericyclic Use pericyclic in a sentence Adjective (not comparable) (botany) of, or relating to a pericycle (chemistry) of, or relating to a pericyclic reaction English Wiktionary. Available under CC-BY-SA license. pericyclic Variant of ...
- adjective see pericycle ... Look at other dictionaries: pericyclic — |perə+ adjective : relating to, consisting of, or located adjacent to or in the pericycle pericyclic cell pericyclic fiber * * * pericyˈclic adjective • • • Main Entry ...
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