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The reaction of 2 reacting components is characterized by the transfer of one atom or group from one reacting component to the another in a coordinated process.
Here, we will learn about some important concept of group transfer. In this context, we will also discuss some important questions.
Definition of Group Transfer in Biology
Group transfer is a reaction where one or more atoms or groups migrate from one molecule to another. A σ – bond connects the molecules. They may resemble sigmatropic and cycloaddition reactions in appearance. However, because it is a bimolecular process, it does not lose a π -bond in order to form a ring via σ – linkage.
Group transfer reactions are classified into two types: ene reactions & diimide reductions. An ene reaction occurs when an alkene with an Allylic Hydrocarbon (ene) thermally reacts with an enophile. Enophiles are compounds with many bonds. The hydrogen atom of the Allylic carbon migrates from alkene to enophile during this reaction.
The π -bond of enophile gets replaced by the 2 σ – bonds with alkene.
Another sort of group transfer process is diimide reduction. By interacting with diimide, an unsaturated hydrocarbon is reduced to generate an alkane (H2N2). Diimide is oxidized to create nitrogen during the process (N2).
Examples for Group Transfer Reaction
The ene reaction, where an Allylic Hydrogen is transferred to an alkene, is the most well-known group transfer reaction.
Ene Reaction
The ene reaction is a chemical reaction that occurs between an alkene containing an allylic hydrogen (the ene) and a molecule which contain a multiple bond (the enophile) to generate a new -bond with ene double bond migration and a 1.5 hydrogen shift. The result is an alkene that has had its double bond moved to the allylic position.
Because this is a Group Transfer pericyclic reaction, it usually necessitates highly activated substrates or high temperatures. Nonetheless, the reaction can be carried out with a wide range of the functional groups which can be attached to the ene & enophile moieties. Many valuable Lewis Acid-catalyzed the ene reactions with excellent yields and selectivities at substantially lower temperatures have also been devised, making the ene reaction a viable C-C forming tool for synthesis of the complex compounds and natural products.
Pericyclic Reaction
The continuous flow of the electrons with π-bonds in cyclic transition state is referred to as a pericyclic reaction. The process of bond-breaking and process of bond-forming processes occur concurrently, without the formation of an intermediate.
A coordinated system of bond production is required for the reaction to be pericyclic. Bond-breaking and bond-formation occur concurrently, but not always to the same extent or rate. The π-bonds usually enter the Cyclic Transition state.
There are 4 types of Pericyclic reaction which are as follows:
- Electrocyclic reaction
- Cycloaddition reaction
- Sigmatropic Rearrangements
- Group Transfer
Functional Group Transfer Reaction
A functional group is transferred from 1 molecule which serves as a donor molecule to the another molecule that functions as the acceptor molecule in Functional Group Transfer Reactions. This reaction can be carried out by transferase, which is involved in a variety of metabolic pathways throughout biology and is essential to some of life’s most important functions.
Transferases are engaged in a wide range of cellular processes. The activity of coenzyme A (CoA) transferase, the action of N-acetyltransferase, and the regulation of the pyruvate dehydrogenase (PDH) are three examples of these reactions.
Conclusion
The ene reactions are the most prevalent of this class, wherein one Hydrogen atom is transferred from an Allylic Alkene to the an electrophilic alkene, followed by the creation of a sigma bond between them and the reorientation of electrons in the allylic alkene system in a coordinated process. The modification of ene reactions, namely the Conia ene & metallo ene reactions, is utilized in organic synthesis to boost yield and enantioselectivity. Group transfer reactions include the reduction of alkenes and alkynes with diimides and the syn-elimination of xanthate esters, selenoxides, amine oxides, and sulfoxides.
