NOTE: Important charges and non-bonding electrons are shown throughout the animation except during the transition state phase.
Click the structures and reaction black arrows in sequence to view the 3D models and animations respectively
The first step of the Z-selective Wittig reaction
is the production of the syn oxaphosphetane via a highly puckered transition state.
The second stage is the decomposition of the oxaphosphetane intermediate which decomposes via a concerted transition state to form the Z alkene and the phosphine oxide.