1429906-83-1Relevant academic research and scientific papers
2-Alkoxy- and 2-alkylthio-2-alkenals in the reactions of electrophilic and nucleophilic addition. DFT study and NBO analysis
Keiko, Natalia A.,Aksamentova, Tamara N.,Chipanina, Nina N.,Verochkina, Ekaterina A.,Vchislo, Nadezhda V.
, p. 2022 - 2032 (2013)
A DFT approach at B3LYP/6-311+G** and M06/6-311+G** levels of theory, and natural bond orbital (NBO) analysis were used to investigate the electron distribution in 3-aryl(hetaryl)substituted 2-methoxy- and 2-methylthiopropenals to predict the possibility of electrophilic (Markovnikov-type) or nucleophilic (Michael-type) addition reactions depending on the nature of substituents. The dependence of the CC bond length on the population ratio of its orbitals, P(πC2=C3*)/ P(πC2=C3), was used to evaluate the donor and acceptor effects of these substituents. The changes in energy values of the frontier orbitals showed that both the electrophilic and nucleophilic abilities of the molecules studied depended on their structure. The change of the polarization direction of the double bond (calculated as the difference of the natural charges formed on its atoms) under the effect of Cβ-substituent allows one to forecast the direction of the polar addition reactions for some representatives of 2-alkoxy- and 2-alkythiopropenals. The slightly different activation energies of hydration of 3-aryl(furyl)substituted 2-methoxypropenals for Markovnikov and Michael additions in acidic medium indicate to equal probability of these processes.
One-pot, three-component cascade synthesis of new tetrasubstituted pyrroles by coupling reaction of 2-functionally substituted 2-alkenals, amines, and nitroethane
Keiko, Natalia A.,Vchislo, Nadezhda V.,Verochkina, Ekaterina A.,Larina, Ludmila I.
, p. 8959 - 8970 (2014)
The reactivity of 2-alkylthio(2-alkoxy)-substituted 3-aryl(hetaryl)propenals in a one-pot, three-component reaction with primary amines and nitroethane has been studied. A method for the synthesis of highly functionalized pyrroles (in 36-80% yield) from 2-alkylthiopropenals has been developed on the basis of this reaction. It is found that the reaction proceeds via formation of the intermediate imine of the starting enal, which undergoes 1,2-addition by nitroethane to give kinetically controlled 2-alkylthio-3-alkylamino-1-aryl(hetaryl)-4-nitropentene. When left to stand, upon heating or under microwave assistance, this adduct can be transformed into the thermodynamically controlled 1,4-adduct. The latter undergoes intramolecular cyclization to afford the target pyrrole. A possibility of such isomerization of addition products of nitroalkane to 2-functionalized α,β-unsaturated imines is revealed for the first time. Scope of the reaction depending upon its conditions as well as structure of the starting substrates and amines has been studied.
