New Synthetic Developments of the [4π + 2π]Cycloreversion

The [4π - 2π]cycloreversion reactions have become a widely used method in organic chemistry, allowing the stereospecific formation or regeneration of an unsaturated bond. More recently, the use of low temperature cycloreversions and/or especially, of flash vacuum thermolysis which avoids any chemical medium, has broadened the scope of this reaction to many reactive molecules. The aim of this review is to present these new synthetic and technical developments. 1. Introduction 2. New Technical Aspects 3. Natural Compounds; Products of Biological or Therapeutical Interest 4. Reactive Molecules, Transient Species 5. Other Synthetic Applications of [4π + 2π]Cycloreversions 6. Conclusion 7. Addenum