Iodine Nitrate1


[14696-81-5]  · INO3  · Iodine Nitrate  · (MW 188.91)

(additions to alkenes;1-7 regioselective and stereoselective introduction of the iodine and oxygen (nitrate) function;1-6,8 in the case of INO2, introduction of iodine and nitro groups;6c,7 iodination of alkylbenzenes9)

Physical Data: prepared in situ in solution.1,2

Solubility: sol most organic solvents.

Form Supplied in: not available commercially; prepared in situ.

Preparative Methods: iodine nitrate (INO3) and iodine nitrite (INO2, more appropriately called nitryl iodide) often show similar chemical properties and can be prepared in situ from iodine and silver nitrate or silver nitrite, respectively. The first reported4 preparation of INO3 was from Mercury(II) Nitrate and Iodine in ether. Silver(I) Nitrate and I2 in ether, acetonitrile, or MeOH, as well as AgNO3 and Iodine Monochloride in CHCl3-pyridine, have been used successfully for additions to alkenes,1,4 although the latter reagent also leads to iodopyridinium adducts.1 Nitrogen Dioxide and I2 have also been used to generate INO3.2 The first reports7 of INO2 addition to alkenes employed Silver(I) Nitrite and I2 in ether to produce iodo nitro adducts, but this reagent also can lead to INO3 adducts.6c,7

A typical procedure for addition of INO3 to alkenes is as follows:1 to AgNO3 (6.8 g, 0.04 mol) in 50 mL dry CHCl3 and 15 mL anhyd. pyridine is added dropwise 6.5 g (0.04 mol) ICl in 20 mL CHCl3. AgCl is filtered and washed with CHCl3-pyridine and 0.04 mol of (E)-4,4-dimethyl-2-pentene is added. After 3 h of stirring, the mixture is poured into ether, filtered, and concentrated to yield 8.7 g (76%) of erythro-3-iodo-4,4-dimethyl-2-pentyl nitrate and 5% of an iodopyridinium salt.

A typical procedure for INO2 addition is as follows:7 AgNO2 (7.55 mmol) and I2 (15.1 mmol) in 75 mL ether is stirred for 30 min and 2-cholestene (7.55 mmol) is added under N2. Workup after 4 h gives 2.033 g (51%) of 2b-iodo-3a-nitrocholestane and 5% (by IR) of 3a-iodo-2b-cholestanyl nitrate.

Handling, Storage, and Precautions: solutions of INO3 or INO2 are not stable on standing. These reagents should be handled in a fume hood.

Additions to Alkenes.

Addition of INO3 to alkenes usually proceeds by ionic attack of I+, leading to a three-membered ring iodonium species. The reaction is stereoselective (anti) and regioselective and steric hindrance plays a role1,2 (see Iodine Azide). With 2-cholestene, the trans-diaxial 3a-iodo-2b-nitrate adduct results either with AgNO3-I2 (79%) or with N2O4 and I2 (60%) (eq 1).2 In contrast, when N2O4 is added to 2-cholestene and I2, the product is 2b-iodo-3a-nitrocholestane (60%) from radical attack by .NO2 (eq 1).7 The same product results from INO2 addition to the alkene.7

In the presence of pyridine, some alkenes give large amounts of an iodopyridinium adduct, e.g. styrene gives 40% and dihydropyran gives 72% (trans) (eq 2).1,5 The INO3 adducts can be converted with Zn-Cu in HOAc into unstable iodohydrins which can be reduced to alcohols (eq 3).1

Addition of INO3 to unsaturated fatty acids gives mixtures of INO3 adducts and iodo ketones.8 The reagent oxidizes secondary alcohols to ketones in fair yields.

Reaction of INO2 with alkenes affords iodo nitro adducts which eliminate HI readily to give unsaturated nitro compounds (eq 4),6a,7 but, in some sugar adducts, elimination of INO2 has been reported.6c AgNO2-I2 has been used to iodinate alkylbenzenes at 20 °C, e.g. toluene gives a 5:2 mixture of p- and of o-iodotoluene.9

1. Lown, J. W.; Joshua, A. V. JCS(P1) 1973, 2680.
2. Kropp, J. E.; Hassner, A.; Kent, G. J. CC 1968, 906.
3. Ritchie, R. G. S.; Szarek, W. A. CC 1973, 686.
4. Birkenbach, L.; Goubeau, J. CB 1934, 67, 1420.
5. Diner, U. E.; Lown, J. W. CJC 1971, 49, 403.
6. (a) Szarek, W. A.; Lance, D. G.; Beach, R. L. CC 1968, 356. (b) Szarek, W. A.; Jewell, J. S.; Szczerek, I.; Jones, J. K. N. CJC 1969, 47, 4473. (c) Szczerek, I.; Jewell, J. S.; Ritchie, R. G. S.; Szarek, W. A.; Jones, J. K. N. Carbohydr. Res. 1972, 22, 163.
7. Hassner, A.; Heathcock, C. H.; Kent, G. J.; Kropp, J. E. Abstracts of Papers, 148th National Meeting of the American Chemical Society, Chicago; 1964, p 29S. (b) Hassner, A.; Kropp, J. E.; Kent, G. J. JOC 1969, 34, 2628.
8. Ahmad, I.; Kaur, A.; Singh, S.; IJC 1989, 28B, 445.
9. Sy, W.-W.; Lodge, B. A. TL 1989, 30, 3769.

Alfred Hassner

Bar-Ilan University, Ramat-Gan, Israel

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