C=C double bond formation

The C=C double bond is one of the most useful functional groups in synthesis, because almost every other group can be introduced from it. Classical eliminations often form it as a mixture of regio- and stereoisomers; the Wittig, Peterson and Julia olefinations place it exactly where a carbonyl group was and allow its E or Z geometry to be chosen.

This topic also covers the addition–cyclization reactions that convert carbonyls into epoxides and cyclopropanes, and the intramolecular syn eliminations of esters, xanthates, N-oxides and selenoxides.