The Julia olefination (also known as the Julia–Lythgoe olefination) is the chemical reaction used in organic chemistry of phenyl sulfones (1) with aldehydes (or ketones) to give alkenes (olefins)(3) after alcohol functionalization and reductive elimination using sodium amalgam or SmI2. The reaction is named after the French chemist Marc Julia. The utility of this connective olefination reaction arises from its versatility, its wide functional group tolerance, and the mild reaction conditions under which the reaction proceeds. All four steps can be carried out in a single reaction vessel, and use of R3X is optional. However, purification of the sulfone intermediate 2 leads to higher yield and purity. Most often R3 is acetyl or benzoyl, with acetic anhydride or benzoyl chloride used in the preparation of 2. History In 1973, Marc Julia and Jean-Marc Paris reported a novel olefin synthesis in which β-acyloxysulfones were reductively eliminated to the corresponding di-, tri-, or tetrasubstituted alkenes. Basil Lythgoe and Philip J. Kocienski explored the scope and limitation of the reaction, and today this olefination is formally known as the Julia-Lythgoe olefination. The reaction involves the addition of a sulfonyl-stabilized carbanion to a carbonyl compound, followed by elimination to form an alkene. In the initial versions of the reactions, the elimination was done under reductive conditions. More recently, a modified version that avoids this step was developed. The former version is sometimes referred to as the Julia-Lythgoe olefination, whereas the latter is called the Julia-Kocienski olefination. In the reductive variant, the adduct is usually acylated and then treated with a reducing agent, such as sodium amalgam or SmI2. Several reviews of these reactions have been published. Reaction mechanism The initial steps are straightforward. The phenyl sulfone anion (2) reacts with an aldehyde to form the alkoxide (3). The alkoxide is functionalized with R3-X to give the stable intermediate (4). The exact mechanism of the sodium amalgam reduction is unknown but has been shown to proceed through a vinylic radical species (5). Protonation of the vinylic radical gives the desired product (6). The stereochemistry of the alkene (6) is independent of the stereochemistry of the sulfone intermediate 4. It is thought that the radical intermediates are able to equilibrate so that the more thermodynamically stable trans-olefin is produced most often. This transformation highly favors formation of the E-alkene. Variations Modified Julia olefination The modified Julia olefination, also known as the one-pot Julia olefination is a