Hypervalent refers to the main group elements that breaks the octet rule and firmly has more than right electrons in it's valence shell. These are non - metallic oxidation reagents.

1. Annu
M.Sc. (Chemistry)
3rd sem.
Roll no:-180000701002
CH. BANSILAL UNIVERSITY BHIWANI
2019-20
Hypervalent organoiodine reagents in organic synthesis
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2. CONTENTS Introduction
 Classification of organic iodine(III) Compound
 Structure of hypervalent iodine reagents.
 Reactivity pattern of hypervalent iodine reagents.
 Ligand exchange.
 Reductive elimination.
 Synthetic methods for hypervalent iodine reagents.
 Synthesis of common iodine reagents.
 Synthesis of diaryliodonium salts.
 Applications of Hypervalent iodine(III)reagents
 Conclusion
 References
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3. Introduction
 Hypervalent iodine reagents have found broad application in organic
chemistry and are frequently used in synthesis.
 It is of great interest to investigate their ability as highly selective oxidants,
electrophilic reagents and to develop new reaction using hypervalent iodine
compounds.
 Because these are non-metallic oxidation reagents, they avoid the issues of
toxicity.
 Hypervalent refers to a main group element that breaks the octet rule and
formally has more than eight electrons in its valence shell.
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4. Classification
 The general classification polyvalent organo iodine
compounds is based on the number of carbon ligand
attached to the central iodine atom.
 The general classes of iodine(III)reagents are :
(1) iodosylarenes ArIO and their acyclic derivatives ArIX2.
(2)five membered iodine heterocycles.
(3) iodonium salt R2IX , and iodonium ylides ArI=CL2.
 The hypervalent iodine species are commonly named
according to N-X-L nomenclature (Martin-Arduengo
designation).
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5. Classification
 The most commonly , 8-I-2 and 10-I-3 are aryl iodane called as
iodinane.
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6. Structure of hypervalent iodine
reagents
 aryl iodane of the type ArIL2 have geometry of pseudo
trigonal bipyramid as shown in figure.
 Bonding in ArIL2 uses a pure 5p orbital in the linear L-I-L bond;
two electrons from the doubly occupied 5p orbital on iodine and
one electron from each of the ligands.
 In the hypervalent model, only non hybridised 5p orbitals of
iodine are involved in bonding.
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7. Reactivity pattern of hypervalent
iodine reagents
 The chemistry of hypervalent iodine is primarily due to its strong
electrophilic character.
 The number of carbon ligands and heteroatom ligands on the
iodine atom determines there reactivity .The stability and
reactivity of hypervalent iodine reagents depend on the
character of hypervalent bond in apical position.
 The first class of iodanes RIL2 are useful agents for oxidation of
various functional groups.The second class of iodanes R2IL are
not good oxidizing agents but transfer one carbon ligand to a
variety of nucleophiles.
 R3I with three carbon ligand are rare and unstable.
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8. Ligand exchange
 Which involves no change in oxidation state.
 The iodine atom of ArIL2 is electrophilic and can react with a
nucleophile to result in the intermediate formation of a trans
tetracoordinated [12-I-4] iodate, with a square-planar
arrangement.
 This is also known as first ligand exchange.this process generally
proceeds with a low energy barrier, and hence is rapid.
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9. Ligand exchange
 Second ligand exchange of ArI(Nu)L may also occur through
similar addition-elimination sequence, depending on the
conditions to ArINu2.
 There are two heteroatom ligand on iodine is essential for the
oxidation reaction, one is used in ligand exchange step and the
other is used in reductive elimination step.
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10. Reductive elimination
 Aryl iodane is known as hypernucleofuge because of its high
leaving group ability than superleaving group like triflate.
 Reductive elimination reaction is very facile and energetically
favourable.
 During this hypervalent iodine atom gets reduced from +3/+5 to
+1 oxidation state.
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11. Synthetic methods of hypervalent
iodine reagents
 Synthesis of these reagent starts from iodobenzene or ring
substituted analogues especially 2-iodobenzoic acid.
 Some common examples of aryl iodanes are (diacetoxyiodo)
benzene (IBD), [bis(trifluoroacetoxy)iodo]benzene (BTI),
iodosobenzene (IOB) and [hydroxy(tosyloxy)iodo]benzene
(HTIB).
 Some commonly used electrophile are chlorine, fluorine,
acetoxy, or trifluoroacetoxy groups, ClF3, t-BuOCl.
 After the formation of hypervalent iodine compounds, iodanes
can exchange their ligand easily with other nucleophiles.
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12. Synthesis of common iodine reagent
(Diacetoxyiodo)benzene (HTIB)
 One of the synthetic routes
for IBD involved the direct
oxidation of iodobenzene in
acetic acid.
 The reaction of p-
toluenesulphonic acid
monohydrate in acetonitrile
at room temperature lead to
HTIB in high yield.
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13. Synthesis of Diaryliodonium salts
 Diaryliodonium salts are either symmetric if R1=R2 or
unsymmetric if R1 R2.
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14. Synthesis of iodonium ylides
 Iodonium ylides are prepared by the reaction of IBD
with an active methylene group in aqueous or
alcoholic alkali medium.
 The tosylate derivative was prepared by treatment of
phosphonium ylides with HTIB in dichloromethane .
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16. Applications of hypervalent iodine
reagents
 Hypervalent aryl iodanes are used extensively in organic
synthesis as highly selective and environmental friendly
oxidizing reagents .
These are broadly classified into following categories:
(1)Oxidation and rearrangements.
(2)Cleavage of carbon-carbon double bonds.
(3)C-Heteroatom bond forming reaction.
(4)Oxidative dearomatization of phenolic substrates.
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17. Oxidation and rearrangements
Synthesis of substituted
tetrahydrofurans
Synthesis of
dihydrofuranobenzofurans
 The tetrahydrofuranylation
proceeded via 1,3-dioxan-2-yl
cation intermediate.
 Then the electrophillic attack
of hypervalent iodine toward
acyloxyalkenes.
 The IBD mediated oxidation
of 4-substituted phenols led
to different
dihydrofuranobenzofurans in
moderate to good yield.
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18. Cleavage of carbon-carbon bond
The reaction of indene with PhI(OH)BF4 obtained in
situation by combination of iodosylbenzene and HBF4
water, led to dialdehyde in moderate yields
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19. C-Heteroatom bond formation
 Carbon heteroatom (N, O, P, S, Se)bond forming
reaction are facilitate by hypervalent iodine reagents
such as aryl iodanes, iodonium salts.
(1) Oxidative amidation of phenols:
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20. Oxidative dearomatization of
phenolic substrates
[Bis(acyloxy)iodo]arenes are commonly used as the
reagents for various synthetically useful oxidative
transformations of phenolic compounds.
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21. Conclusion
We have established a highly stereoselective
intramolecular diamination using a chiral hypervalent
iodine.
 The hypervalent iodine is very useful oxidizing
properties, combined with environmental character
and commercial availability.
Hypervalent iodine reagents in particular (IBD) and
(BTI) have low toxicity, easy handling, and reactivities
similar to that of heavy metal reagents.
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22. References
 Perkins, C. W.; Martin, J. C.; Arduengo, A. J.; Lau, W.;
Alegria, A.; Kochi, J. K. J. Am. Chem. Soc. 1980,102,
7753.
 (a)Yusubov, M. S.; Gilmkhanova, M. P.; Zhdankin, V.
V.; Kirschning, A. Synlett 2007, 563.
(b)Yusubov, M. S.; Chi, K. W.; Park, J.Y.; Karimov, R.;
Zhdankin, V. V. Tetrahedron Lett. 2006, 47, 6305.
 Prakash, O.; Kaur, H.; Pundeer, R.; Dhillon, R. S.;
Singh, S. P. Synth. Commun. 2003, 33, 4037.
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