Distinction between the reactivity of phosphorus ylide vs sulfur ylide with the carbonyl compounds : Simplicity and logic

Department of Clinical and Experimental Pharmacology, School of Tropical Medicine, Kolkata-700 073, India E-mail : cskatichandan@gmail.com Department of Chemistry, St. Paul's Cathedral Mission College, Kolkata-700 009, India Wittig olefination and Corey-Chaykovsky epoxidation of carbonyl compounds are well-documented classical and synthetically useful name reactions which are taught in great details in both undergraduate and post-graduate curricula of organic chemistry. Whilst similar reagents (a phosphorus ylide in Wittig olefination and a sulfur ylide in Corey-Chaykovsky epoxidation) and same substrate (a carbonyl compound) are deployed in both reactions, their outcome is strikingly different. Yet any discussion of reasons behind this differential behavior is conspicuously absent in almost all of the textbooks and the issue remains a perpetual source of confusion among students. In this article an attempt has been made to shed light on this problem and dispel those confusions through qualitative discussion of the theories and experimental results concerning the mechanistic details of these reactions