Vinylcyclopropane-cyclopentene rearrangement

The vinylcyclopropane rearrangement or vinylcyclopropane-cyclopentene rearrangement is a ring expansion reaction, converting a vinyl-substituted cyclopropane ring into a cyclopentene ring.

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.

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.

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