[3 + 2]‐Cycloaddition von Methylazid an 5‐Alkyliden‐1,4‐dihydro‐1,4‐dimethyl‐5H‐tetrazole

Abstract

Natriumhydrid deprotoniert die 5-Alkyl-l,4-dimethyltetrazoliumlonen 4 zu. den luftempfindlichen, gelben, destillierbaren 5-Alkyliden-l,4-dihydro-SH-tetrazolen 1. Daneben 1,4-dibydro-1,4-dimethyi5H-te~zolesSodium hydride deprotonates the 5-alkyl-I ,4dimethyltetrazolium ions 4 affording the air-sensitive, yellow, distillable 5-alkylidene-1,4-dihydro-5H-tetraoles 1. In addition, small amounts of the spiro compound Sa are formed through cleavage of 4a by nucleophiles yielding methyl azide followed by [3 + 23 cycloaddition of the latter to give la. In separate experiments, methyl aide reacts smoothly with 1 at temperatures as low as 0-20°C producing the spiro compounds 5 which exhibit surprising thermal stability. The structures of the cycfoadducts 5 are based on spectra and the base-induced cleavage of 5b into methyl azide and aminotrjazole 16. The latter is synthesized independently from tmtbutylacetonitrile and methyl azide.

Triazenes by Acid‐Mediated Opening of the Dihydro‐1,2,3‐triazole Ring of1,3‐Dipolar Cycloadducts of Organic Azides to Cyclic Ketene N,N‐Acetals

“…Attempts at separation by extracting a benzene solution of a mixture containing 1d with a saturated aqueous solution of potassium dihydrogen phosphate afforded a surprising result: Not the 5-amino-1H-1,2,3-triazole as intended but 1d was extracted into the aqueous layer from which it could be recovered quantitatively after addition of concentrated sodium hydroxide solution. [9] NMR spectra of solutions in potassium [D 2 ]dihydrogen phosphate/deuterium oxide that were obtained from 1a and d showed that protonation drastically changes the spirocyclic structures. The spiro carbon-13 signals at 100-105 ppm [9,10] are no longer observed while 1 H and 13 C NMR signals that are characteristic of 5-alkyl-1,4-dimethyltetrazolium ions make their appearance.…”

“…[9] NMR spectra of solutions in potassium [D 2 ]dihydrogen phosphate/deuterium oxide that were obtained from 1a and d showed that protonation drastically changes the spirocyclic structures. The spiro carbon-13 signals at 100-105 ppm [9,10] are no longer observed while 1 H and 13 C NMR signals that are characteristic of 5-alkyl-1,4-dimethyltetrazolium ions make their appearance. [11] These results indicate that the dihydrotriazole ring of 1a and d was opened to yield a triazene.…”

“…[9,10] Those cycloadducts 1 that have a proton attached to their triazole carbon (R 3 = H), e. g. 1d, are prone to base-induced cleavage of the dihydrotetrazole ring yielding methyl azide and 5-amino-1H-1,2,3-triazoles, which occasionally are undesired byproducts. Attempts at separation by extracting a benzene solution of a mixture containing 1d with a saturated aqueous solution of potassium dihydrogen phosphate afforded a surprising result: Not the 5-amino-1H-1,2,3-triazole as intended but 1d was extracted into the aqueous layer from which it could be recovered quantitatively after addition of concentrated sodium hydroxide solution.…”

2,3,4,5-Tetrahydro-2,4-diimino-1,3,5-triazin-1-ium salts in the reaction of carbodiimides with N-alkylnitrilium salts

“…Cycloadditions of organic azides to nitrilium salts 1 lead to trisubstituted tetrazolium salts. [8][9][10][11] These reactions are dominated by a concerted mechanism. 9 However, the cycloaddition of the azide ion N 3 -to nitrilium ions is assumed to proceed via a two-step mechanism.…”

“…9 However, the cycloaddition of the azide ion N 3 -to nitrilium ions is assumed to proceed via a two-step mechanism. [9][10][11][12][13] Previously, we reported the synthesis of 1,2,4-oxadiazonium salts by the cycloaddition of nitrile oxides to nitrilium and cyanamidium salts. 14 Also, the addition of nitrilium salts to α,β-unsaturated carbonyl compounds led to the formation of 4H-1,3-and 6H-1,3-oxazinium salts 2-azonia-allene salts by a 1-5 hydrogen shift followed by cyclization.…”