| Autor: |
Alajarin M; Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence 'Campus Mare Nostrum', Universidad de Murcia, E-30100 Murcia, Spain., Cutillas-Font G; Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence 'Campus Mare Nostrum', Universidad de Murcia, E-30100 Murcia, Spain., Lopez-Leonardo C; Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence 'Campus Mare Nostrum', Universidad de Murcia, E-30100 Murcia, Spain., Orenes RA; ACTI, Universidad de Murcia, E-30100 Murcia, Spain., Marin-Luna M; Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence 'Campus Mare Nostrum', Universidad de Murcia, E-30100 Murcia, Spain., Pastor A; Departamento de Química Orgánica, Facultad de Química, Regional Campus of International Excellence 'Campus Mare Nostrum', Universidad de Murcia, E-30100 Murcia, Spain. |
| Abstrakt: |
This work describes the unprecedented intramolecular cyclization occurring in a set of α-azido-ω-isocyanides in the presence of catalytic amounts of sodium azide. These species yield the tricyclic cyanamides [1,2,3]triazolo[1,5- a ]quinoxaline-5(4 H )-carbonitriles, whereas in the presence of an excess of the same reagent, the azido-isocyanides convert into the respective C-substituted tetrazoles through a [3 + 2] cycloaddition between the cyano group of the intermediate cyanamides and the azide anion. The formation of tricyclic cyanamides has been examined by experimental and computational means. The computational study discloses the intermediacy of a long-lived N -cyanoamide anion, detected by NMR monitoring of the experiments, subsequently converting into the final cyanamide in the rate-determining step. The chemical behavior of these azido-isocyanides endowed with an aryl-triazolyl linker has been compared with that of a structurally identical azido- cyanide isomer, experiencing a conventional intramolecular [3 + 2] cycloaddition between its azido and cyanide functionalities. The synthetic procedures described herein constitute metal-free approaches to novel complex heterocyclic systems, such as [1,2,3]triazolo[1,5- a ]quinoxalines and 9 H -benzo[ f ]tetrazolo[1,5- d ][1,2,3]triazolo[1,5- a ][1,4]diazepines. |
