Radical-mediated desulfonylation reactions with group 14 metallo hydrides : synthesis of (a-fluoro)phosphonates and (a-fluoro)vinyl silanes
Master of Science (MS)
First Advisor's Name
Stanislaw F. Wnuk
First Advisor's Committee Title
Second Advisor's Name
Third Advisor's Name
Date of Defense
The sulfone group is a well-established activating moiety important in many organic transformations. Standard procedures for desulfonylation [Al(Hg), or Na(Hg)] were ineffective for the removal of the pyridin-2-ylsulfonyl group from the α-carbon of phosphonic esters. Prompted by these results, we undertook a study for the synthesis of α-(arylsulfonyl)phosphonates, and their fluorination with Selectfluor to produce α-fluoro-α-(arylsulfonyl)phosphonates, Radical mediated hydrogenolysis of α-fluoro-α-(arylsulfonyl)phosphonates using BujSnH gave (α-fluoro)phosphonates. We observed that the yield for the desulfonylation reaction depends on the n-deficiency effect and increase in the order pyrimidinyl > pyridinyl > phenyl sulfonyl.
The (α-fluoro)phosphonates were employed as convenient precursors in the Homer-Wadsworth-Emmons (HWE) reaction to provide (α-fluoro)vinyl sulfones. The vinyl and (α-fluoro)vinyl sulfones underwent substitutive silyl and germyl- desulfonylation to yield vinyl and (α-fluoro)vinyl silanes and germanes via an addition-elimination mechanism. The vinyl tris(trimethylsilyl)silanes were employed as nucleophiles (under oxidative conditions) in palladium-catalyzed cross coupling reactions with iodobenzene and bromobenzene.
Garica, Pedro Israel Jr., "Radical-mediated desulfonylation reactions with group 14 metallo hydrides : synthesis of (a-fluoro)phosphonates and (a-fluoro)vinyl silanes" (2004). FIU Electronic Theses and Dissertations. 3524.
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