Page 248 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements
P. 248
GROUP 16 ELEMENTS: THE CHALCOGENS
228
REVIEW PROBLEM 6.11
In the Kornblum oxidation, a primary alkyl halide is oxidized to the aldehyde with
DMSO and NaHCO , typically with microwave heating:
3
O
DMSO
R Br
NaHCO 3 (2 equiv.) R H
Δ (microwave)
Suggest a mechanism by analogy with the Swern oxidation.
REVIEW PROBLEM 6.12*
A rather remarkable reaction of alkyl sulfoxides is the Pummerer rearrangement,
where treatment with acetic anhydride (or another activator) results in rearrangement
to an -acetoxythioether:
− S R 2
O R 1
Ac O
2
S R 2 O
R 1 +
O
Suggest a mechanism. Hint: A pericyclic reaction is involved after the initial
acetylation.
6.10 SULFUR YLIDES AND SULFUR-STABILIZED CARBANIONS
Like a phosphonium ion, a sulfonium ion can stabilize an adjacent carbanion center.
+ + −
NaH
Me S CH 3 DMSO Me S CH 2 (6.92)
2
2
+
Thus, a pK of 16.3 has been estimated for the Ph(Me)(PhCH )S cation for the hydro-
2
a
gens shown in bold, which is about the same as that for the OH group of an alcohol. The
anionic carbon in dimethylsulfonium methylide, as the above product is called, reacts with
