Dyotropic migration

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 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. 

Dyotropic rearrangement is an uncatalysed process in which two a bonds simultaneously migrate intramolecularly by a dyotropic transition state 202 and has been observed in organosilylhydroxylamine derivatives 201 (equation 59). 

Migration of a substituent on a disilene giving the corresponding silylene [pathway (3)] should be considered as a pathway for the /AZ-isomerization but occurs usually with much higher activation energies than pathways (1) and/or (2). The pathway (3) and related dyotropic rearrangement are discussed in detail in Section IV.A.3. 

Dyotropic rearrangements are defined as the uncatalyzed concerted rearrangements in which two groups migrate intramolecularly and exchange positions (equation 1). Although... 

The 1,2-silyl migration shown in equation 3 may also proceed via a dyotropic... 

A dyotropic rearrangement was reported for the redistribution of the ligands in transition metal complexes25. Several other dyotropic silyl migrations have been reported26-29. 

Dyotropic rearrangements are uncatalyzed, intramolecular pericyclic reactions in which two (T-bonds simultaneously migrate [158b]. 

Dyotropic rearrangements were defined as a new class of pericyclic valence isomerizations in which two o--bonds (i.e., groups) migrate... 

Scheme 1. Stereochemistry of dyotropic silyl group migration.

Utilizing appropriate compounds in the fluorenyl series it was shown that the silyl groups migrate 100% intramolecularly (ii). On the other hand, allyl migration was not found to be strictly intramolecular, mtermolecularity amounting to about 28%. This means that at least the latter portion does not adhere to a strict dyotropic mechanism. 

Type II dyotropic rearrangements involve double migration but no positional exchange. One such possibility is the squaric acid system in which thermally induced migration of the two ester functions toward the two carbonyl oxygen atoms is an orbital symmetry-allowed [ 7g -1- ... 

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). 

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