Nitryl iodide

The regioselecdve adthdon of nitryl iodide to dlkenes, fohuwed by base-induced eliminadon, gives nitrodlkenes. Nittyl iodide is generally prepared by the reaction of AgNO and iodine. 

Replacement of silver nitrite by inexpensive sodiiunor potassium nitrite enhances the imlity of this process Treatment of alkenes v/ith sodiiun nitrite and iodine in ethyl acetate and water in the presence of ethylene glycol gives conjngatednitroalkenesin49-82% yield The method for generation of nitryl iodide is improved by the treatment of iodme v/ith potassium nitrite complexed v/ith 18-crovm-6 in THF under sonicadon, as shovmin Eq 2 32 ... 

The synthetic applications of this reagent to the synthesis of nitroalkenes have been known since the 1960s.60 Nitration of alkenes with nitryl iodide, generated in situ from iodine and silver nitrite, is convenient for the synthesis of P-nitrostyrenes with various functional groups.61 This method is applied to the synthesis of ortho-methoxylated phenylisopropylamines, which are potent serotonine agonists (Eq. 2.31).62... 

Nitration of acetylenes with nitryl iodide followed by elimination of HI gives nitroacetylenes, but nitroacetylenes are too thermally unstable to be useful for organic synthesis.77 Recently, nitro-trimethylsilyl-acetylenes are prepared as stable nitroacetylenes by the reaction of bis(trimethylsily)acetylene with nitronium tetrafluoroborate (Eq. 2.39).78... 

While the hydrolysis of N205 is believed to represent its major loss process, there are other possibilities that have potentially interesting implications under certain conditions. For example, N2Os reacts with the components of sea salt particles such as NaCl, NaBr, and Nal to form nitryl chloride, nitryl bromide, and nitryl iodide, respectively (e.g., Finlayson-Pitts et al., 1989a, 1989b Behnke and Zetzsch, 1990 Zetzsch and Behnke, 1992 Junkermann and Ibusuki, 1992 George et al., 1994 Behnke et al., 1994, 1997 Leu et al., 1995 Fenter et al., 1996 Barnes et al., 1991 Schweitzer et al., 1998) ... 

Iodination of arenes.1 These two reagents generate nitryl iodide, which can iodinate arenes, particularly methylarenes, at 28°. The yield increases with the number of methyl substituents, being 90-95% with tri- and tetramethylbenzenes.1... 

The use of the pseudohalogen nitryl iodide, prepared in situ from iodine and silver nitrite, has been found to add to an alkene in what is strictly an anti-Markownikov fashion. The explanation for this lies in that nitryl iodide adds in a radical manner, initially forming the more stable secondary radical after addition of NO2.115 Treatment of 3-0-acetyl-5,6-dideoxy-1,2-0-isopropylidene-a-D-xy/o-hex-5-enofuranose with nitryl iodide was found to afford an unstable adduct, with the nitro group appended to C-6, and iodine attached to the more substituted C-5.116-118 Similarly, treatment of benzyl 2-0-benzyl-3,4-dideoxy-a-D-g/ycero-pent-3-enopyranoside (70, Scheme 19) with nitryl iodide afforded the unstable adduct 71, which, upon exposure to mild base (NaHC03), afforded the eliminated product, namely benzyl 2-0-benzyl-3,4-dideoxy-4-nitro-a-D-g(ycew-pent-3-enopyranoside (72). The eliminated product was then readily converted into benzyl 2-0-benzyl-3,4-dideoxy-(3-L-r/ireo-pentopyranoside (73) by reduction with sodium borohydride. Addition of deuteride using NaBD4 led to axial deuteration atC-3. 

Treatment of an epoxide, namely methyl 2,3-anhydro-4,6-0-benzylidene-oi-D-allopyranoside (78, Scheme 21), with nitryl iodide using methanol as the solvent has been reported.123 Rather than the expected nitration, opening of the epoxide occurred to afford 30% of methyl 4,6-0-benzylidene-3-0-methyl-oi-D-glucopyranoside (79), 10% of methyl 4,6-0-benzylidene-2-0-methyl-a-D-altropyranoside (80), and a water-soluble material. The water-soluble material was later determined to be a mixture of the 2-0- (81) and 3-0-methyl (82) products, with the benzylidene acetal removed, a result consistent with a later study.124 Performing the reaction in the absence of the silver salt resulted solely in formation of the water-soluble product. The preponderance of the diequatorial product 81 is in violation of the Flirst-Plattner rule, which predicts more of the diaxial product. The authors explanation for the anti-Fiirst-Plattner addition is as follows. 

The use of iodine-containing pseudohalogens has been demonstrated to cause a variety of side reactions. Treatment of methyl 5-0-benzoyl-2,3-dideoxy-3-D-g/ycero-pent-2-enofuranoside (83, Scheme 22) with nitryl iodide afforded none of the desired addition product, but gave a quantitative yield of furfuryl benzoate (86). The same result was obtained by treating 83 with iodine nitrate, or with iodine alone.125 The rationale for this undesired result lies in the ability of iodine to act as a Lewis acid, polarizing the glycosidic bond, generating an oxacarbenium cation, which then decomposes to the stable aromatic 86. 

The introduction of a nitro group into the alkenes under consideration may be achieved by addition of nitryl iodide (IN02). In the case of alkene 22, this addition, followed by reduction with sodium borohydride, led32 to 3-deoxy-1,2 5,6-di-0-isopropylidene-3-C-(nitromethyl)-a-D-allofuranose (52). Light-induced addition of 1,3-dioxolane to alkenes 15a and 22 has also been reported.47 The resulting adducts, 53 and 54, respectively, are of value as they contain a potential aldehydo function. 

Nitryl iodide, from iodine with silver nitrite or from NO2 and iodine, adds to alkenes, generally in ether at room temperature, by a radical mechanism. Yields are 50-90%. The products yield nitroalkenes on treatment with base, a sequence used recently in the preparation of intermediates (ArCH—CMeNOa) for amphetamine analogs. The reaction is also a key step in the a-methylenebuty-rolactone synthesis shown in Scheme... 

Reaction with Nitryl Iodide and Nitronium Tetrafluoroborate... 

Differing from the reaction with dinitrogen tetroxide/iodine (see following section), the addition of nitryl iodide to ( )-l,2-diphenylethylene gave a mixture of diastereomers, as determined by H-NMR spectroscopy129. 

An attempt to apply this method to the functionalization of glycals has been reported. The addition of nitryl iodide to benzyl 2-0-benzyl-3,4-dideoxy-ot-D-g/ycero-pent-3-enoside gave a crystalline adduct with unspecified yield and unspecified regio- and stereochemistry130 dehy-drohalogenation to the a,/ -unsaturated nitro derivative was easily accomplished. 4,6-O-Ben-zylidene-2,3-dideoxy-at-D-eo>fftro-hex-2-enoside did not react with nitryl iodide130. 

This is surprising, since the reaction of dinitrogen tetroxide with (E)-, 2-diphenylethylene in diethyl ether produced a 3 2 mixture of diastereomeric l,2-dinitro-l,2-diphenylethanes134 The reaction of 2-cholestene with dinitrogen tetroxide/iodine afforded 2/ -iodo-3a-nitro-5oi-chole-stane, this was also the product obtained by the addition of nitryl iodide (see previous section). 

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