Hypervalent Iodine Compounds
Weaker and longer than covalent linkages, hypervalent bonds are the result of a linear three-center, four-electron (3c-4e) electronic distribution (hypervalent model). Hypervalent iodine reagents are useful synthetic tools due to their low toxicity, ready availability, and ease of handling.
Specific hypervalent iodine reagents: Dess-Martin Periodinane, Iodosobenzene diacetate, Iodosobenzene bis(trifluoroacetate), Iodosylbenzene, 2-Iodoxybenzoic Acid, Iodobenzene Dichloride
Recent Literature
[dibmim][BF4] can be used for the oxidation of alcohols to
carbonyl compounds. This oxidizing agent offers a high degree of selectivity
for the oxidation of primary alcohols to carbonyl compounds without
oxidation to carboxylic acids in ionic liquids. [dibmim][BF4] can
be reused after oxidation with peracetic acid.
W. Qian, E. Jin, W. Bao, Y. Zhang, Angew. Chem. Int. Ed., 2005,
44, 952-955.
A highly efficient 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) catalyzed
reaction using recyclable 1-chloro-1,2-benziodoxol-3(1H)-one as the
terminal oxidant allows the conversion of various alcohols to their
corresponding carbonyl compounds in high to excellent yields at room temperature
in ethyl acetate, which is an environmentally friendly organic solvent.
X.-Q. Li, C. Zhang, Synthesis, 2009,
1163-1169.
2-Iodoxybenzenesulfonic acid, which can be generated in situ from
2-iodobenzenesulfonic acid sodium salt, is a much more active catalyst than
modified IBXs for the oxidation of alcohols with Oxone. Highly efficient and
selective methods for the oxidation of alcohols to carbonyl compounds such as
aldehydes, carboxylic acids, and ketones were established.
M. Uyanik, M. Akakura, K. Ishihara, J. Am. Chem. Soc., 2009,
131, 251-262.
Stable, microcrystalline 2-iodylphenol ethers were prepared by the
dimethyldioxirane oxidation of the corresponding 2-iodophenol ethers.
2-Iodylphenol ethers can selectively oxidize sulfides to sulfoxides and alcohols
to the respective aldehydes or ketones.
A. Y. Koposov, R. R. Karimov, I. M. Geraskin, V. N. Nemykin, V. V. Zhdankin, J. Org. Chem., 2006,
71, 8452-8458.
A mild, efficient and environmentally friendly oxidation of sulfides to
sulfoxides with a recyclable ion-supported hypervalent iodine reagent tolerates
hydroxyl, nitrile, methoxy, carbon-carbon double bonds, and ester
functionalities. Aliphatic and aromatic sulfides are selectively oxidized to the
corresponding sulfoxides at room temperature in excellent yields without
over-oxidation.
W. Qian, L. Pei, Synlett,
2006, 709-712.
Various α-tosyloxyketones were efficiently prepared in high yields from the
reaction of ketones with m-chloroperbenzoic acid and p-toluenesulfonic acid in
the presence of a catalytic amount of iodobenzene.
Y. Yamamoto, H. Togo, Synlett,
2006, 798-800.
α-Acetoxylation of ketones catalyzed by iodobenzene using acetic anhydride and
30% aqueous hydrogen peroxide as the oxidant is an effective and economical
method for the preparation of α-acetoxy ketones in good yields.
J. Sheng, Y. Li, M. Tang, B. Gao, G. Huang, Synthesis, 2007,
1165-1168.
Oxidation of alkyl aryl ketones in the presence of Oxone, trifluoroacetic anhydride
and a catalytic amount of iodobenzene affords α-hydroxyalkyl aryl
ketones in good yield. This method provides an effective and economical entry
for the α-hydroxylation of ketones.
C. Chen, X. Feng, G. Zhang, Q. Zhao, G. Huang, Synthesis, 2008,
3205-3208.
A new and reliable method for the direct construction of biologically important
aryl lactones and phthalides from carboxylic and benzoic acids is based on
selective benzylic C-H abstraction in the presence of hypervalent iodine(III)
reagents and KBr.
T. Dohi, N. Takenaga, A. Goto, A. Maruyama, Y. Kita, Org. Lett., 2007,
9, 3129-3132.
Alkylcarboxamides can be converted to the respective alkylcarbamates by
Hofmann rearrangement using hypervalent iodine species generated in situ from
PhI and Oxone in methanol. In addition, substituted benzamides can be converted
to the respective quinone derivatives by treatment with Oxone and iodobenzene in
aqueous acetonitrile.
A. A. Zagulyaeva, C. T. Banek, M. S. Yusubov, V. V. Zhdankin, Org. Lett., 2010,
12, 4644-4647.
Dehydrosulfurization using a hypervalent iodine(III) reagent enables a simple
and efficient preparation of symmetrical and unsymmetrical carbodiimides from
the corresponding thioureas. The oxidation afforded carbodiimides in excellent
yields and high selectivity. A possible mechanism for the transformation is
proposed.
C. Zhu, D. Xu, Y. Wei, Synthesis, 2011,
711-714.
Iodobenzene can be used as a recyclable catalyst in combination with m-chloroperbenzoic
acid as the terminal oxidant for an efficient and regioselective monobromination
of electron-rich aromatic compounds. The bromination of electron-rich aromatic
compounds with lithium bromide was fast in tetrahydrofuran at room temperature,
providing regioselective monobrominated products in good yields.
Z. Zhou, X. He, Synthesis, 2011,
207-209.
Poly{[4-(hydroxy)(tosyloxy)iodo]styrene} was efficient in the halotosyloxylation
reaction of alkynes with iodine or NBS or NCS. The polymer reagent could be
regenerated and reused.
J.-M. Chen, X. Huang, Synthesis, 2004,
1557-1558.
A Rh(II)-catalyzed oxidative coupling of aldehydes and sulfonamides provides
N-sulfonylcarboxamides in one step. Various sulfonamides were found to react
with aromatic and aliphatic aldehydes to afford the desired products in very
good yields.
J. Chan, K. D. Baucom, J. A. Murry, J. Am. Chem. Soc., 2007,
129, 14106-14107.
A desulfurizing difluorination reaction of benzyl sulfides having an
electron-withdrawing group such as an ester, a ketone, a nitrile, or an amide in
the presence of IF5 gave gem-difluoro compounds in good yield.
T. Fukuhara, S. Hara, Synlett, 2009,
198-200.
