Amyl nitrite reagent

Amyl nitrite reagent lb 115 Amylose la 173 a-Amyrin la 44,63,69 P-Amyiin la 69... 

It was shown that amide formation can be suppressed by the appropriate choice of reaction conditions, such as homogeneous solutions, e.g. in DMF, DMSO, HMPA, high acidity and low temperatures (-30 to -5°C). If the peptide hydrazide contains acid-labile protecting groups, e.g. trityl, 2-(4-biphenyl)propyloxycarbonyl, tert-butyloxycarbonyl, tert-butyl esters and ethers, the temperature has to be kept below -20 °C. Generally, tert-butyl or butyl nitrite is used as the organic nitrite, and for sterically hindered peptides amyl nitrite is employed. The time required for full conversion of the hydrazide into the azide may vary between 5 to 30 min and can be monitored by spray reagents (see experimental procedure below). 

The reagent also can be generated in situ from an alkyl nitrite (ethyl nitrite or amyl nitrite) and hydrochloric acid or hydrochloric acid in methanol, ethanol, or acetic acid. ... 

The high reactivity of indole is shown up well by the ease with which it undergoes substitution with weakly electrophilic reagents such as benzenediazonium chloride and nitrosating agents. Indoles react rapidly with nitrous acid indole itself reacts in a complex manner, but 2-methylindole gives a 3-nitroso-product cleanly. This can also be obtained by a base-catalysed process using amyl nitrite as a source of the nitroso... 

A good source of 7V-(2-pyridylmethyl)anilines and A/ <4-pyridylmethyl)anilines is the reaction of 2- and 4-pyridinemethanol with anilines in the presence of potassium hydroxide at high temperature. Thus, a mixture of 4-pyridinemethanol, p-ethoxyaniline, potassium hydroxide, and a trace of amyl nitrite gives AT-(4-pyridylmethyl)-p-ethoxyaniline (IX-244). Amyl nitrite is not a necessary reagent. 

Use of (-amyl chloroformate to give the /-amyloxycarbonylamino acids has some limitations since strictly anhydrous conditions are required. Sakakibara5 has converted the reagent into the more useful (-amyl azidoformate (b.p. 81.5—82°/51—53 mm.) by reaction with anhydrous hydrazine to give (-amyl carbazate followed by reaction with sodium nitrite (compare synthesis of (-butyl azidoformate [see 1, 84]). The azidoformate reacts with amino acids in aqueous dioxane in the presence of triethylamine to give (V-r-amyloxycarbonylamino acids in yields of 70-95%. 

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