Page 310 - Arrow Pushing in Inorganic Chemistry A Logical Approach to the Chemistry of the Main Group Elements

THE HALOGENS
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alcohol to the pentavalent iodine, with loss of one of the acetate ligands. Mechanistic details
are not shown below, but an S 2-Si mechanism seems plausible:
N
OAc OAc
AcO AcO
OAc O
I I H
1 2
R R CHOH C
O O (7.105)
− HOAc 1
R R 2
O O

3
Abstraction of an -proton from the alkoxide then results in a ketone and an aryl- -iodane,
as shown below.
−
OAc OAc
AcO OAc
O O
I H − I
C − OAc
O O + C (7.106)
1 − HOAc R 1 R 2
R R 2
O O

7.13 PERIODIC ACID OXIDATIONS

Compared with the higher-valent iodine reagents discussed so far, the use of periodic acid
(H IO ) as a reagent in organic chemistry goes back quite a bit further in time. It has been
5
6
widely used in the cleavage of vicinal diols to carbonyl compounds:
O O
HO OH
H 5 IO 6
C C C + C (7.107)
R 1 R 4 R 1 R 2 R 3 R 4
R 2 R 3
As with lead tetraacetate, the first steps of diol cleavage involve formation of a cyclic ester:
−
O
+
HO OH −
I HO O
HO OH OH
HO
OH I
OH
H O O H H O + OH O H
C C C C
R 1 R 4 R 1 R 4
R 2 R 3 R 2 R 3 (7.108)
−
O
−
HO O HO OH
HO + I
I + HO OH
OH O O
− HOH − H
O OH O H
C C
C C R 1 R 4
R 2 R 3
R 1 R 4
R 2 R 3