|
The vinylcyclopropane rearrangement or vinylcyclopropane-cyclopentene rearrangement is a ring expansion reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring.〔E M Mil'vitskaya, A V Tarakanova and Alfred F Plate. Thermal Rearrangements of Vinylcyclopropanes. Russ. Chem. Rev. 1976;45:469-478. .〕〔Z. Goldschmidt and B. Crammer. Vinylcyclopropane rearrangements. Chem. Soc. Rev. 1988;17:229-267. .〕 Intense experimental as well as computational investigations have revealed that mechanistically, the vinylcyclopropane rearrangement can be thought of as either a diradical-mediated two-step and/or orbital-symmetry-controlled pericyclic process. The amount by which each of the two mechanisms is operative is highly dependent on the substrate. Due to its ability to form cyclopentene rings the vinylcyclopropane rearrangement has served several times as a key reaction in complex natural product synthesis. ==Origins and history== In 1959, a young research chemist with Humble Oil and Refining (Esso, now Exxon) named Norman P. Neureiter was instructed to find new uses for the excess butadiene produced from one of the refinery processes. Discussions about carbene chemistry with one of the company's most respectable consultants at the time, William von Eggers Doering, then a professor at Yale, led the young Ph.D. graduate from Northwestern University to follow a recent procedure combining both, carbenes and butadiene. In particular the procedure described the reaction of 1,3-butadiene with carbenes generated from the action of base on chloroform or bromoform, which had been studied previously by Doering. Neureiter then took the resulting 1,1-dichloro-2,2-dimethylcyclopropane and under pyrolysis conditions (above 400 °C) discovered a rearrangement to 4,4-dichlorocyclopentene which today is considered to be the first thermal vinylcyclopropane-cyclopentene rearrangement in history. The corresponding all-carbon version of the reaction was independently reported by Emanuel Vogel and Overberger & Borchert just one year after the Neureiter publication appeared. Interestingly Doering, although actively interacting with Humble Oil and Refining - and therefore also with Neureiter - as a consultant, in a 1963 publication stated the following : ''"CREDIT for discovery that vinylcyclopropane rearranges to cyclopentene is due to Overberger and Borchert, and Vogel et al., who appear to have developed several examples of the rearrangement independently."'' The development of further vinylcyclopropane rearrangement variants didn't take long as demonstrated by Atkinson & Rees in 1967, Lwowski in 1968. and Paladini & Chuche in 1971. It is remarkable that the classical vinylcyclopropane rearrangement was discovered after two of its heteroatom variants had already been reported for almost 30 years and 12 years, respectively. Although it is believed that the vinylcylcopropane rearrangement must have occurred during Nikolay Demyanov's preparation of vinylcyclopropane by Hofmann elimination at elevated temperatures in 1922 the cyclopropylimine-pyrroline rearrangement by Cloke in 1929 and Wilson's cyclopropylcarbaldehyde-2,3-dihydrofuran rearrangement in 1947 are really the only examples of vinylcyclopropane-like rearrangements. 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「Vinylcyclopropane rearrangement」の詳細全文を読む スポンサード リンク
|