Heating azide

Yet another route to intermediate 39 was reported by Ciufolini and Bishop [36]. In their synthesis, heating azide 41 in refluxing o-dichloroben-zene produced /i-carbolinc 42 in 83% yield (Fig. 13). Oxidation with NaC102 followed by esterification with diazomethane produced 39 in 97% yield. Since intermediate 41 could be prepared in just four steps in 74% overall yield from quinoline 40 and o-azidobenzaldehyde, this approach represented a fairly quick and efficient route to 39. 

Sulfuric Acid. Forms explosive solution in 50% H2S04 unless acid is quite cold.9 Water. Violent reaction occurs when water is added to strongly heated azide.10... 

Concerning heat sensitive groups (question I), it is, for example, not advisable to heat azide moieties (cf. reaction 166 167 in Section IV,D)... 

The TT-cyclization of A/ -acyliminium ions onto aromatic rings is a useful method for the preparation of isoquinolines fused with heterocycles. Heating azide 102 with one of the compounds methyl (5)-mandelate (103) or methyl (i )-mandelate (63) in toluene provides the carbamates 104 and 105 respectively. DIBAL reduction of 104 or 105 with DIBAL in toluene... 

Attempts to add nitrenes derived by heating azides to alkynes are usually thwarted by the facile addition of the azide 1,3-dipole to the triple bond with the formation... 

A related sequence was used by Kozikowski and Greco for a total synthesis of ( )-clavicipitic acid (107) (1984JOC2310). On heating azide 104 at 190 °C, the initially formed triazoHne intermediate 105 underwent loss... 

Preparation of Acylamines. Heating azides with anhydrous organic acids usually gives rise to acylamines, along with more or less of the sym-urea. This reaction proceeds through mbced anhydrides of the... 

All the azides are potentially dangerous, and liable to detonate on heating, but those of the alkali and alkaline earth metals can be heated with caution if pure they then evolve pure nitrogen. 

Acetanilide from acetophenone. Dissolve 12 g. of acetophenone in 100 ml. of glacial acetic acid containing 10 g. of concentrated sulphuric acid. To the stirred solution at 60-70°, add 9 8 g. of sodium azide in small portions at such a rate that the temperature does not rise above 70°. Stir the mixture with gentle heating until the evolution of nitrogen subsides (2-3 hours) and then allow to stand overnight at room temperature. Pour the reaction mixture on to 300 g. of crushed ice, filter the solid product, wash it with water and dry at 100°. The yield of crude acetanilide, m.p. 111-112°, is 13 g. Recrystallisation from water raises the m.p. to 114°. 

Phenylhydrazine condenses with carbon disulphide to yield the phenylhydrazine salt of P phenyldithiocarbazic acid (I), which on heating at 96-98 until the first evolution of ammonia is detectable affords diphenylthiocarb-azide (II) ... 

Acyl azides may loose N2 on heating and rearrange to isocyanates (Curtius rearrangement), which may be solvolyzed. Some of the possibilities of classical carboxyl conversions are exemplified in the schemes below, which are taken from a triquinacene synthesis (R. Russo, 1971 C. Merder, 1973) and the ergotamine synthesis of A. Hofmann (1963). 

Sulfonium ylides may be added to C N double bonds to yield aziridines in a formal [1 -t-2]-cycloaddition. Alkyl azides are decomposed upon heating or irradiating to yield ni-trenes, which may also undergo [ 1 + 2 -cycloaddition reactions to yield highly strained hetero-cycles (A.G. Hortmann, 1972). 

The Curtms rearrangement has been used to prepare 5-aminothiazole (11) (60.61), 4-methyl-5-aminothiazole. 2-chloro-5-aminothiazole (58), and 2.4-dimethyl-5-aminothiazole (62) (Scheme 11). Heating the corresponding azides yield carbamates that resist hydrolysis but react with acetic anhydride to give the 5-acetylaminothiazoles. 

Silver Azide. Silver a2ide, AgN, is prepared by treating an aqueous solution of silver nitrate with hydrazine (qv) or hydrazoic acid. It is shock-sensitive and decomposes violendy when heated. 

Nitrogen and sodium do not react at any temperature under ordinary circumstances, but are reported to form the nitride or azide under the influence of an electric discharge (14,35). Sodium siHcide, NaSi, has been synthesized from the elements (36,37). When heated together, sodium and phosphoms form sodium phosphide, but in the presence of air with ignition sodium phosphate is formed. Sulfur, selenium, and tellurium form the sulfide, selenide, and teUuride, respectively. In vapor phase, sodium forms haHdes with all halogens (14). At room temperature, chlorine and bromine react rapidly with thin films of sodium (38), whereas fluorine and sodium ignite. Molten sodium ignites in chlorine and bums to sodium chloride (see Sodium COMPOUNDS, SODIUM HALIDES). 

Cyclopropenyl azides (350), the obvious precursors to cyclopropenylnitrene and hence possibly azetes by ring expansion of the latter, give 1,2,3-triazines on heating or irradiation (78HC(33)5). 

The ether is distilled gently from a steam bath, preferably through a short fractionating column nitrogen wUl be evolved at the same time. When the volume of the contents of the flask has reached about 400 ml., the flask is heated strongly on the steam bath for about 15 minutes to complete the decomposition of the azide (Note 9). The flask is removed from the steam bath. 

Explosions involving flammable gases, vapours and dusts are diseussed in Chapter 6. In addition, eertain ehemieals may explode as a result of violent self-reaetion or deeomposition when subjeeted to meehanieal shoek, frietion, heat, light or eatalytie eontaminants. Substanees eontaining the atomie groupings listed in Table 7.7 are thermodynamieally unstable, or explosive. They inelude aeetylides and aeetylenie eompounds, partieular nitrogen eompounds, e.g. azides and fulminates, peroxy eompounds and vinyl eompounds. These unstable moieties ean be elassified further as in Table 7.8 for peroxides. Table 7.9 lists a seleetion of potentially-explosive eompounds. 

A mixture of the epoxide ca. 5 mmol), sodium azide (6 g, activated by the method of Smith) and 0.25 ml of concentrated sulfuric acid in 70 ml of dimethyl sulfoxide is heated in a flask fitted with a reflux condenser and a drierite tube on a steam bath for 30-40 hr. (Caution carry out reaction in a hood.) The dark reaction mixture is poured into 500 ml of ice water and the product may be filtered, if solid, and washed well with water or extracted with ether and washed with sodium bicarbonate and the water. The crude azido alcohols are usually recrystallized from methanol. 

A solution of 5 g (14 mmoles) of 5a-cholest-2-ene in 100 ml ethyl acetate and 8 ml of 2.8 M (22 mmoles) cyanogen azide (CAUTION See Chapter 15 and ref. 139b) in ethyl acetate is heated at 50-53° for 24 hr, during which time about 22 mmoles of nitrogen is evolved. Solvent is removed by evaporation and the residue is applied in benzene to a column of 160 g of neutral alumina (activity grade III). Elution with petroleum ether-benzene (1 1) gives 1.6 g of... 

The 1,2,3,4-thiatriazoles are unstable. They decompose on heating— in some cases even at room temperature—and in many cases they melt with detonation. Accordingly the Ng-group has not been stabilized much by ring closure. The compounds behave in this respect similarly to azides and this fact doubtlessly delayed the recognition of their true nature. On heating with a solvent the thermal decomposition of 5-aryl-1,2,3,4-thiatriazoles proceeds according to Eq. (4). By the photochemical decomposition small amounts of the isothiocyanate, RNCS, are formed in addition to the nitrile. ... 

Diamines formed upon photolysis of 6-quinolyl azide in isopropyl-, n-butyl-, and n-hexylamines are very unstable, so they were cyclized to the corresponding 1-substituted imidazo[4,5-/]quinolines by heating the residue obtained after evaporation of the photolysis solvent with formic acid at reflux (82JCS(P 1)421). Instead... 

Disubstituted diacetylenes react with benzyl azide upon long heating in toluene (12-16 h, yield 67-70%) (82ZOR1619). Comparison of the reactivity and... 

Intramolecular dipolar azide-olefin cycloaddition of 723 took place upon heating in benzene to afford 724 (83JA3273). An alternative rearrangement process can take place upon photolysis of 724 to give 725. Mesylation of 4-(3-hydroxypropyl)-2,4,6-trimethyl-2,5-cyclohexadiene-l-one (78JA4618) and subsequent treatment with sodium azide in DMF afforded the respective azide 726 which underwent intramolecular cycloaddition to afford the triazoline 727 (83JOC2432). Irradiation of 727 gave the triazole derivative 728 (Scheme 126). 

In the original work (72), the authors stated that heating of 42 with excess sodium iodide did not result in further exchange. The extensive studies of Stevens and co-workers (96, 97) on the displacement reactions of compounds much related to 40, indicate that the C-4 sulfonate group can indeed be displaced by various nucleophiles. In fact compound 42 and its C-4 epimer (43) (d-threo) have been subjected to displacement reactions with benzoate (38), acetate and azide (98) ions to give the corresponding C-4 inverted products. 

---