Page 256 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements
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GROUP 16 ELEMENTS: THE CHALCOGENS
236
REVIEW PROBLEM 6.17*
Consider the following DAST deoxofluorination of an enolizable ketone:
F
O F F
DAST F
+ +
CH CI 2
2
60% 30% 10%
Besides the desired difluoroalkane, two vinyl fluoride by-products are also obtained.
Rationalize the various products in terms of a mechanistic picture.
6.13 MARTIN SULFURANE
The tetravalent sulfur reagent Martin sulfurane permits dehydration of alcohols under
remarkably mild conditions:
Ph
R F
CF 3
O O
CF 3
Ph Ph
S = S
Ph Ph
O Ph O
R F
F 3 C CF 3
Martin sulfurane
The reagent is expensive, given the fluorinated alkoxy (R O) ligands, but is ideally suited
F
for valuable and/or sensitive substrates. It’s prepared from diphenyl sulfide and potassium
1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanolate as follows:
Ph R F
− − O
O Br +
Ph 2 S, Br 2 S R F OK Ph
O Ph S (6.111)
CF CCl 4 Ph
Ph 3
CF 3 O
F 3 C
Ph R F
F C
3
