Isopentyl nitrite

The benzodiazepinone 26 condenses with 3-melhylbulyl nitrite (isopentyl nitrite) in the presence of potassium lerl-butoxide to give the oxime 27, which is converted into the amine 28 by catalytic hydrogenation.227... 

The diazotization of heteroaromatic amines is basically analogous to that of aromatic amines. Among the five-membered systems the amino-azoles (pyrroles, diazoles, triazoles, tetrazoles, oxazoles, isooxazoles, thia-, selena-, and dithiazoles) have all been diazotized. In general, diazotization in dilute mineral acid is possible, but diazotization in concentrated sulfuric acid (nitrosylsulfuric acid, see Sec. 2.2) or in organic solvents using an ester of nitrous acid (ethyl or isopentyl nitrite) is often preferable. Amino derivatives of aromatic heterocycles without ring nitrogen (furan and thiophene) can also be diazotized. 

In the older literature isopentyl nitrite is called isoamyl nitrite. 

In the context of diazoazoles, 5-diazotetrazole (2.22) should be mentioned. It was obtained by dropwise addition of isopentyl nitrite to a solution of 5-amino-lH-tetra-zole in a 4 1 mixture of tetrahydrofuran and aqueous hydrochloric acid. The diazo-nium chloride can be extracted into ether. The extremely explosive solid diazonium... 

In most cases diazonium salts are not isolated, but are converted into products by reactions that can be carried out in situ. Moreover, it is actually recommended not to isolate these salts, not even for purification purposes, as many of them have a tendency to explode. In addition, the high solubility of most diazonium salts in water makes precipitation from this medium difficult. Therefore, to obtain solid diazonium salts the recommended method for many decades was to carry out diazotizations in ethanol followed by precipitation with ether. As inorganic salts of nitrous acid are scarely soluble in ethanol, Knoevenagel recommended alkyl nitrites (ethyl or isopentyl nitrite) as diazotization reagents as long ago as 1890. Various other solvents have subsequently been used for diazotizations with alkyl nitrites (see Saunders and Allen, 1985, p. 23 ff.), but as a method for obtaining solid diazonium salts this has been superseded by the isolation of diazonium tetrafluoroborates and, to a lesser degree, of hexafluorophosphates. 

Meerwein-Gomberg reactions between pyridinediazonium salts and furans fail because the Sandmeyer reaction supervenes, and the isopentyl nitrite method also gives poor results.264 Fortunately, photolysis of 3-... 

The reaction of 571 with isopentyl nitrite in the presence of potassium tert-butoxide gave 5-oximinotriazinobenzodiazepine 576, which was hydrogenated over Raney nickel to give aminotriazinobenzodiazepine 577 (88EUP272868). 

The furazan ring can be constructed by the one-pot reaction of iV-(5,5-dimethyl-3-oxocyclohexenyl)-.S,.S-diphenyl-sulfilimine 272 with isopentyl nitrite <2006SC2087> and also by a one-pot procedure from sulfinimines 273, without isolation of the nitroso intermediates, in refluxing toluene (Scheme 71) <2002T10073>. 

To avoid the above mentioned problems, diazonium salts were synthesized by diazotizing amino compounds with isopentyl nitrite in acetic acid containing a strong acid such as trifluoromethanesulfonic acid. After completion of... 

Decyl nitrite, 3364 f Ethyl nitrite, 0867 f Isopentyl nitrite, 1996 f Isopropyl nitrite, 1262 f Methyl nitrite, 0455 f Pentyl nitrite, 1998 f Propyl nitrite, 1265... 

From limited data the generalization has been made that this method fails for the synthesis of 1-substituted dibenzofurans and for the synthesis of 4-substituted dibenzofurans unless the amino group and the potential 4-substituent are in the same ring. These generalizations are not substantiated in the synthesis of polychlorodibenzofurans. Polychloro-2-phenoxy-anilines are poorly soluble and nonbasic so that the usual method is precluded. In these cases aprotic diazotization with isopentyl nitrite in tetrachloroethylene at 80 C is the method of choice. Yields, as determined by GLC, are usually of the order of 40-50%. The yields of pure isolated... 

In a well-ventilated hood, to a stirred solution of 4.7 gm (0.08 mole) of nor-bornene and 7.02 gm (0.06 mole) of isopentyl nitrite in 10 ml of ethanol, cooled to 0°C in an ice-salt bath, is added dropwise, over a hr period, a solution of 10 gm (0.59 mole) of 48 % hydrobromic acid in 12 ml of ethanol. After the addition has been completed, stirring in the ice bath is continued for another 20 min. The product is isolated by filtration and washed with ethanol. Yield 8.1 gm (80%), m.p. 134°-136°C. On recrystallization from chloroform, the melting point is raised to 138°-139°C. 

Nitrosyl formate may be generated in situ by treating isopentyl nitrite with anhydrous formic acid. This reagent evidently adds to olefins such as cyclohexene, styrene, norbomene, trans-3-hexene, and 2,3-dimethylbutene to give nitrosoformates. While the first three olefins were converted into dimeric products, 2,3-dimethylbutene produced a 50-50 mixture of the monomer and the dimer (as a blue oil). The product of the reaction with trans-3-hexene contained some of the corresponding oximino formate. 

To 150 ml of cold anhydrous formic acid is added dropwise, with stirring, a solution of 16.4 gm (0.2 mole) of cyclohexene and 46.8 gm (0.4 mole) of isopentyl nitrite. The white solid which forms is filtered off and recrystallized from ethanol to yield 18.3 gm (59%), m.p. 149°-150°C. 

Iso-AMYL NITRITE Amyl Nitrite, 3-Metylbutyl Nitrite, Isopentyl Nitrite Flammable Liquid, 11 i NL 2 ... 

Donor-substituted 1-aminomethylcyclopropanes 108 110 and tosylhydrazones of 1-donor-substituted cyclopropyl ketones 111 can undergo ring enlargement to cyclobutanones through deamination. To this purpose, aminomethylcyclopropanes were diazotized with sodium nitrite 108-110 or isopentyl nitrite 109 in acidic medium and tosylhydrazones were decomposed in basic medium.111 The rearrangements proceed via diazonium ions and are especially useful for the construction of bicyclic systems. For examples of these rearrangements see 1,108 2,109 3,109 4,110 5,111 6 and 7.1 1... 

The homolytic arylation of benzo[6]furan has been studied using aryl radicals generated by decomposition of 1,3-diaryltriazenes in the presence of isopentyl nitrite at 120 °C (79JHC97), or phenyl radicals produced by the decomposition of N- nitrosoacetanilide at 40 °C. The major position of attack is the 2-position (75.9%), but some occurs at the 4-(17.5%) and 7-positions (6.6%). Benzo[6]furan is 8.3 times more reactive than benzene and 1.26 times more reactive than benzo[6 Jthiophene. 

The carbanion formed when chromanone is treated with a base such as sodium methoxide reacts with ethyl formate to give the 3-hydroxymethylene derivative (S95) and such compounds have been used as intermediates (72JHC1341,70IJC203). When treated with isopentyl nitrite, chromanones usually give the 3-isonitroso derivative but this reaction occasionally behaves anomalously without obvious reason. For example, 7-methoxychromanone is readily converted into its 3-isonitroso derivative (596), but with 7-hydroxychromanone the reaction fails <77HC(31)207). 

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