The mechanism of the reaction of hydrazines with α,β-unsaturated carbonyl compounds to afford 2-pyrazolines (4,5-dihydro-1H-pyrazoles): experimental and theoretical results

The reaction of hydrazines with a,b-unsaturated carbonyl compounds to afford 2-pyrazolines was studied using a dissymmetric chalcone (phenyl/p-tolyl) and three hydrazines, hydrazine itself, phenylhydrazine and thiosemicarbazide. Several products were identified, and some reaction paths established t...

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Bibliographic Details
Authors: Hoz Ayuso, Antonio de la, Alkorta, Ibón, Elguero, José
Format: article
Publication Date:2021
Country:España
Institution:Universidad de Castilla-La Mancha
Repository:RUIdeRA. Repositorio Institucional de la UCLM
OAI Identifier:oai:ruidera.uclm.es:10578/38427
Online Access:https://hdl.handle.net/10578/38427
Access Level:Embargoed access
Keyword:Pyrazolines, Dihydropyrazoles, Hydrazones, IRC, GIAO, NMR
Description
Summary:The reaction of hydrazines with a,b-unsaturated carbonyl compounds to afford 2-pyrazolines was studied using a dissymmetric chalcone (phenyl/p-tolyl) and three hydrazines, hydrazine itself, phenylhydrazine and thiosemicarbazide. Several products were identified, and some reaction paths established thanks to the evolution of 1H and 13C NMR spectra with time. Theoretical calculations on energies and chemical shifts were of paramount importance to ascertain the structure of some products. For important steps, the transition states were calculated while IRCs proved necessary to find some unexpected intermediates.