The Wittig reaction

CONTENTS
I. Introduction 347
II. Alkylidenephosphoranes 347
III. Mechanism and stereochemistry of the Wittig reaction 351
IV. Synthesis of natural polyacetylenic compounds 352
V. Synthesis of terpenes, carotenoids, and vitamin A 353
VI. Synthesis of steroids and vitamin D₂ 357
VII. Prospects for future uses of the Wittig reaction in the synthetic field 358