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A dyotropic Reaction (from the Greek ''dyo'', meaning two) in organic chemistry is a type of organic reaction and more specifically a pericyclic valence isomerization in which two sigma bonds simultaneously migrate intramolecularly.〔''Dyotropic Reactions: Mechanisms and Synthetic Applications'' Israel Fernandez Fernando P. Cossıo and Miguel A. Sierra Chem. Rev. 2009, Article ASAP 〕 The reaction type is of some relevance to organic chemistry because it can explain how certain reactions occur and because it is a synthetic tool in the synthesis of organic molecules for example in total synthesis. It was first described by Manfred T. Reetz in 1971 〔''Dyotropic Rearrangements, a New Class of Orbital-Symmetry Controlled Reactions''. Type I Manfred T. Reetz Angewandte Chemie International Edition in English 1971 Volume 11 Issue 2, Pages 129 - 130 〕〔''Dyotropic Rearrangements, a New Class of Orbital-Symmetry Controlled Reactions. Type II'' Angewandte Chemie International Edition in English 1971 Volume 11, Issue 2, Date: February 1972, Pages: 130-131 Manfred T. Reetz 〕 :Dyotropic rearrangement In a type I reaction two migrating groups interchange their relative positions and a type II reaction involves migration to new bonding sites without positional interchange. ==Type I rearrangements== In type I rearrangements (Y-A-B-X conversion to X-A-B-Y) the two migrating groups are oriented trans to each other and as a result of the rearrangement they migrate to opposite sides. The first example of a dyotropic rearrangement involving a carbon-carbon bond was reported by Cyril A. Grob and Saul Winstein.〔''Organische und biologische Chemie Mechanismus der Mutarotation von 5,6-Dibromcholestan'' C.A. Grob, S. Winstein Helvetica Chimica Acta Volume 35 Issue 3, Pages 782 - 802 1952 〕 They observed the interconversion of 2 bromine atoms in a certain steroid. In a straightforward example the two bromine atoms in 3-tert-butyl-trans-1,2-dibromohexane mutarotate by heating.〔''Substituent effects on the formation and equilibration of trans-1,2-dibromocyclohexanes'' P. L. Barili, G. Bellucci, G. Berti, F. Marioni, A. Marsili, I. Morelli, J. Chem. Soc. D, 1970, (21),1437-1438 〕 In the transition state both bromine atoms connect symmetrically two both carbon atoms on opposite sides and the reaction is concerted. Stepwise mechanisms in dyotropic reactions have also been investigated. :Dyotropic reaction Barili 1970 In organic synthesis an important application is the conversion of 4-substituted-gamma-lactones to butyrolactones. Type I dyotropic rearrangements also occur around carbon-oxygen bonds for example is the thermal equilibration of RRSi1R3C-O-Si2R3 to RRSi2R3C-O-Si1R3. The 1,2-Wittig rearrangement can also be considered an example of this reaction type. More dyotropic reactions are found involving N-O bonds and N-N bonds. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dyotropic reaction」の詳細全文を読む スポンサード リンク
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