Dyotropic rearrangement rearrangements

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... 

An irreversible dyotropic rearrangement of fluoro-substituted tris(silyl)hydroxyl-amines (127) (128) has been reported and ab initio and density functional calculations for model compounds have confirmed the dyotropic course of this rearrangement. ... 

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). 

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. 

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. 

A similar rearrangement is observed between tetrasilyldisilenes 34 and 35 [Eq. (56)].14 The activation free energy for the rearrangement from 35 to (Z)-34 (or ( )-34) is 17.4kcalmol-1 at 283 K, which is ca. 1.7 kcal mol-1 larger than that for the /i,Z-isomerization and 7.7 kcal mol-1 smaller than those for the dyotropic type rearrangement of tetraaryldisilenes.96... 

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

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 type rearrangements were also found in stable disilenes (equation 5)31,32. The rates of these rearrangements were strongly dependent on the substituents. Thus, for the rearrangement in l,l-dimesityl(2,2-dixylyl)disilenes, 70 days were needed at 298 K to attain equilibrium, while the rearrangement in tetrasilyldisilenes was completed within 10 days at 273 K. 

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