Julia reaction Kocienski modification

In a pivotal modification of the direct olefination reaction Kocienski and his coworkers [10] showed that the use of l-phenyl-lff-tetrazol-5-yl sulfones, preferentially with NaHMDS or KHMDS as the base and DME as the solvent, provides olefins in excellent yields and stereoselectivity with respect to -isomers. The modified version of the direct olefination reaction has frequently been referred to as the Julia-Kocienski olefination reaction. 

Modified Julia reactions The Kocienski modification of the Julia reaction Direct Coupling of Carbonyl Compounds and Alkenes... 

A stereoselective construction of the Z)-e/yr/tro-azidosphingosine characteristic trans double bond was accomplished by Panza and co-workers by condensation reaction between tetradecanol and a heterocyclic sulfone derived from diethyl Z)-tartrate, following the Kocienski modification of the Julia-Lythgoe olefination. Alcohol 71 was first converted into the 1-phenyl-l//-tetrazole-5-yl thioether under Mitsunobu conditions and then oxidized to 73 in 80% yields. A solution of sulfone 73 in DME at -55 "C was treated with KHMDS to give a stable anion of compound 73, which was then reacted with tetradecanal to give compound 74 in 53% yield. The compound 74 can be efficiently transformed into the target, 3-(9-(4-methoxybenzyl)-azidosphingosine, with reported procedure. 

A study carried out by Kocienski and Lythgoe flrst demonstrated the trans selectivity of the Julia coupling process. The authors found the i uctive elimination could best be carried out with the acet-oxy or benzoyloxy sulfones. If the lithio sulfone derivative is used for addition to the carbonyl, the reaction can be worked up with acetic anhydride or benzoyl chloride to obtain the alkene precursor. In cases where enolization of the carbonyl is a complication, the magnesium derivative can frequently be used successfully. A modification of the reductive elimination was found to be most effective. Methanol, ethyl acetate/methanol or THF/methanol were the solvents of choice and a temperature of -20 C was effective at suppressing the undesired elimination of the acetoxy group to produce the vinyl sulfone. With these modifications of the original procedure, the ability of the reaction to produce dienes as well as rran.r-disubstituted alkenes was demonstrated, llie diastereoisomeric erythro- and threo-acetoxy sulfones could be separated and it was demonstrated that both isomers were converted to the rrans-alkene. It... 

---