Dyotropic reactions

The thermal rearrangement of allyl(silylmethyl) ethers, an example of a dyotropic reaction, in which the silyl and allyl groups exchange their positions, exhibits only a very small solvent dependence this is as expected for a concerted reaction according to Eq. (5-55) [158b] ... 

A special term ( dyotropic reaction see also Ref 222.374) proposed to denote the noncatalyzed processes in the course of which two o-bonds migrate simultaneously and intramolecularly, and a general theory of such reactions was developed In accordance with the definitions given in Ref. the rearrangement of ion (77) by the concerted route should be considered as a dyotropic reaction of type I. 

While never observed, this reaction is the simplest possible in the category of type I dyotropic reactions. These are defined as reactions involving migration of m-7T or potentially 77 atoms from one site to another with concomitant migration of n atoms from the migration terminus to the reaction origin (Scheme 3.5). 

Type II dyotropic reactions were defined in a companion paper to that of the type I reaction. Here, two sets of atoms are transferred simultaneously from two atoms to two other atoms, resulting in transposition of tt bond(s). The simplest example is that of transfer of a hydrogen atom from each carbon of ethane to the carbons of ethylene (Scheme 3.7). 

For leading references and a theoretical study, see Frontera, A. Suher, G. A. Deya, P. M. /. Org. Chem. 1992, 57, 6731. The analogous intramolecular rearrangement is known as a dyotropic reaction. 

Fernandez I, Bickelhaupt FM, Cossio FP (2012) Type-I dyotropic reactions understanding trends in barriers. Chem Eur J 18 12395... 

From these observations, however, it cannot be concluded whether the double hydrogen migration in ionized [2] occurs in a concerted or stepwise fashion. If the hydrogen atoms would migrate in a concerted fashion, then it is an example of a dyotropic reaction, being defined as an uncatalysed process in which two o-bonds simultaneously, but not necessarily via a fully symmetrical mode, migrate intramolecularly. 

A dyotropic rearrangement is an uncatalyzed process in which two a bonds simultaneously migrate intramolecularly. There are two types. The above is an example of type 1, which consists of reactions in which the two a bonds interchange positions. In type 2, the two a bonds do not interchange positions. An example is... 

Dyotropic Rearrangements and Related o--cr Exchange Processes, 16, 33 Electronic Effects in Metallocenes and Certain Related Systems, 10, 79 Electronic Structure of Alkali Metal Adducts of Aromatic Hydrocarbons, 2, 115 Fast Exchange Reactions of Group I, II, and III Organometallic Compounds, 8, 167 Fischer-Tropsch Reaction, 17, 61 Flurocarbon Derivatives of Metals, 1, 143... 

Dyotropic rearrangements are uncatalyzed concerted dihydrogen exchange reactions, another class of orbital symmetry controlled processes, which involve the simultaneous migration of two cr-bonds. These conversions can be both thermal and photochemical. They can be subdivided into two types (1) reactions in which two migrating cr-bonds interchange their positions (equation 78), and (2) reactions without such positional interchange (equation 79)91,92. 

Furthermore, a brief review of dyotropic rearrangements starting with the hypothetical transformations of 1,2-disubstituted cyclobutenes was published98 in which two types of these processes were described and a general theory covering such rearrangements was outlined. Quantum chemical calculations of the reaction barrier for the dihydrogen... 

To explore the dyotropic rearrangement of silyl hydroxylamines, Schmatz, Klinge-biel and colleagues studied the behaviour of 0-lithium-Af,Af-bis(f-butyldimethylsilyl) hydroxylamine 207 in the presence of chlorotrimethylstannane (equation 62). They found that the primarily formed Af,Af-bis(f-butyldimethylsilyl)-0-(trimethylstannyl)hydroxyl-amine 208 underwent a dyotropic rearrangement to form 209. This reaction mechanism is corroborated by quantum chemical calculations partly employing an effective core potential for tin. 

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