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Chapter 2
Synthesis of substituted pyrimidines via Wittig
Figure-24
De-Jun Dong et al. 46 have developed a simple and efficient protocol to
improve the stereoselectivity significantly for the olefination reaction of semistabilized
triphenylphosphonium ylides by replacing the aldehydes used in the Wittig
reaction with N-sulfonyl imines, which possess distinct electronic and steric
properties relative to aldehydes (Figure-25).
Figure-25
Douglass F. Taber et al. 47 were utilized a Potassium hydride in paraffin KH(P)
as a base in Wittig condensation of phosphonium salt with aromatic, aliphatic, and
α,β-unsaturated aldehydes in THF proceeds with high Z selectivity (Figure-26).
Figure-26
Fulvia Orsini et al. 48 has synthesized α,β-unsaturated esters in open
atmosphere via mild and efficient one-pot Wittig reactions performed in both water
and sodium dodecyl sulfate (SDS)-water solution(Figure-27).
Figure-27
Y.k. Liu et al. 49 has discovered a highly stereoselective tandem Michael
addition-Wittig reaction of (3-carboxy-2-oxopropylidene) triphenylphosphorane and
α,β-unsaturated aldehydes gives multifunctional 6-carboxycyclohex-2-en-1-ones in
excellent diastereo- and enantioselectivities by employing the combined catalysis of a
bulky chiral secondary amine, LiClO 4 , and DABCO (Figure-28).
Department of Chemistry, Saurashtra university, Rajkot-360005 53