Electrocyclic Ring Opening of cis-Bicyclo[m.n.0]alkenes: The Anti-Woodward–Hoffmann Quest
✍ Scribed by Carlos Silva López; Olalla Nieto Faza; Ángel R. de Lera
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 206 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0947-6539
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The dubbed anti‐Woodward–Hoffmann ring‐opening reaction of cis‐bicyclo[4.2.0]oct‐7‐ene to yield cis,cis‐cycloocta‐1,3‐diene has been intensively studied with robust, high‐level computational methods. This reaction has been found to proceed through a conrotatory allowed pathway to afford cis,trans‐cycloocta‐1,3‐diene followed by E to Z isomerization, instead of a disrotatory forbidden pathway, as suggested. Computational calculations of kinetic isotope effects are consistent with this interpretation and the experimental values. The study of lower bicyclic homologues with [3.2.0], [2.2.0] and [2.1.0] skeletons indicates the feasibility of a mechanistic change towards the anti‐Woodward–Hoffmann disrotatory path. This is clearly favored for the ring opening of the highly strained cis‐bicyclo[2.1.0]pent‐2‐ene and is highly competitive with the conrotatory path for cis‐bicyclo[2.2.0]hex‐2‐ene. Therefore, the rearrangement of the smallest bicyclic cyclobutene is predicted computationally to be an anti‐Woodward–Hoffmann disrotatory electrocyclic ring‐opening reaction.