Wittig Reaction of Semi-Stabilised Ylides with Benzaldehydes Studies on the Effect of ortho Position
Introduction
In organic chemistry, Wittig reaction has attracted both immense interest and controversies among synthetic chemists. It continues to generate contentious issues especially where lithium salt-free reactions are involved. Much of these controversies arise from the original Wittig proposal that the reaction progresses via oxaphosphetane, an idea that was vehemently opposed almost immediately [1]. The topic has received several excellent reviews concerning reaction mechanisms [2, 3]. Mutual consensus among researchers is that all Wittig reactions share a common experimental effect for all phosphonium-based ylide reactions. Similarly, selectivity is consistent for cis-oxaphosphetane together with its derivative products such aserythro-β-hydroxyphosphonium and Z-alkene salt in reactions where aldehydes bearing a heteroatom on the β-position as a substituent are involved. This effect usually operates for both aliphatic aldehydes and benzaldehydes, while in the absence of a substituent heteroatom they do not operate [4].
