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- Title
Mechanistic Aspects on [3+2] Cycloaddition (32CA) Reactions of Azides to Nitroolefins: A Computational and Kinetic Study.
- Authors
Kawamura, Meire Y.; Alegre‐Requena, Juan V.; Barbosa, Thaís M.; Tormena, Cláudio F.; Paton, Robert S.; Ferreira, Marco A. B.
- Abstract
[3+2] cycloadditions of nitroolefins have emerged as a selective and catalyst‐free alternative for the synthesis of 1,2,3‐triazoles from azides. We describe mechanistic studies into the cycloaddition/rearomatization reaction sequence. DFT calculations revealed a rate‐limiting cycloaddition step proceeding via an asynchronous TS with high kinetic selectivity for the 1,5‐triazole. Kinetic studies reveal a second‐order rate law, and 13C kinetic isotopic effects at natural abundance were measured with a significant normal effect at the conjugated olefinic centers of 1.0158 and 1.0216 at the α and β‐carbons of β‐nitrostyrene. Distortion/interaction‐activation strain and energy decomposition analyses revealed that the major regioisomeric pathway benefits from an earlier and less‐distorted TS, while intermolecular interaction terms dominate the preference for 1,5‐ over 1,4‐cycloadducts. In addition, the major regioisomer also has more favorable electrostatic and dispersion terms. Additionally, while static DFT calculations suggest a concerted but highly asynchronous Ei‐type HNO2 elimination mechanism, quasiclassical direct‐dynamics calculations reveal the existence of a dynamic intermediate.
- Subjects
NITROALKENES; RING formation (Chemistry); AZIDES; STRAIN energy; INTERMOLECULAR interactions
- Publication
Chemistry - A European Journal, 2022, Vol 28, Issue 69, p1
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.202202294