Direct observation and characterisation of 3-azido-2H-azirines: postulated, but highly elusive intermediates

Abstract

The title compounds, including the parent 3-azido-2H-azirine, were generated by low-temperature photolysis of the corresponding 1,1-diazidoethenes, and characterised not only by trapping reactions, but also by direct detection using NMR and in situ IR spectroscopy.

Nucleophilic Attack of Azide at Electrophilic Azides: Formation of N6 Units in Hexazene and Aminopentazole Derivatives

“…The N ‐azido compound 17 can easily be handled in solution at −40 °C; however, rapid decay with a half‐life t 1/2 of approximately 16 min, which was measured by collecting the liberated dinitrogen gas, was observed at −30 °C . Hence, 17 is significantly less stable than 13 , and consequently, 17 did not undergo a clean trapping reaction with cyclooctyne . On the other hand, solutions of the aminopentazole derivative 7 can be utilized for NMR spectroscopy at +10 °C, and a half‐life t 1/2 of around 11 min was roughly estimated at 21 °C.…”

Nucleophiler Angriff von Azid auf elektrophile Azide: Bildung von N6‐Einheiten in Hexazen‐ und Aminopentazolderivaten

“…Die N ‐Azidoverbindung 17 war in Lösung bei −40 °C einfach zu handhaben; bei −30 °C setzte allerdings ein rascher Zerfall mit einer Halbwertszeit t 1/2 ≈16 min ein, was über das Auffangen des freigesetzten Stickstoffgases gemessen wurde . Folglich ist 17 deutlich weniger stabil als 13 , und deshalb ging 17 keine saubere Abfangreaktion mit Cyclooctin ein . Andererseits konnten Lösungen des Aminopentazolderivats 7 bei +10 °C für die NMR‐Spektroskopie herangezogen werden, während bei 21 °C eine Halbwertszeit t 1/2 ≈11 min grob abgeschätzt wurde.…”

Synthesis of various functionalized 2H‐azirines: An updated library

“…Correspondingly, Banert group studied similar type of low‐temperature photolysis reactions [55–61], such as, several open‐chain 1,2‐diazidoethenes were photolyzed to yield 2‐azido‐2 H ‐azirines (Scheme 33) [55] and gem‐bromoiodo‐substituted vinyl azide photolyzed to thermally unstable 2‐bromo‐2‐iodo‐2 H ‐azirine (Scheme 34) [56].…”

“…Similarly, the irradiation of 1,1‐diazidoethenes will produce the short‐lived intermediate 3‐azido‐2‐cyano‐2 H ‐azirine‐2‐carboxylate A . The consumption of A was very slow at −60°C, whereas a rapid formation of 1 H ‐1,2,3‐triazole was observed at −20°C by cycloaddition with the help of Cyclooctyne (Schemes 38 and 39) [60].…”