Abstract
An eco-benign synthesis of pyrimidine derivatives 2a,b containing different functional groups with different electronic character starting from nitroalkenes 1a and 2b has been described. The structures for 1a and 2a,b have been characterized by single crystal X-ray diffraction analysis. The thermal data of the molecules pointed towards important structural aspects of their stability. The mechanism of their thermal decomposition is discussed. The thermodynamic parameters of the dissociation steps were evaluated and discussed. DFT calculations reveal that the compound 1a possesses a high calculated dipole moment value (8.28 D) which indicates its high reactivity towards its surrounding molecules.
Highlights
Pyrimidine and its derivatives, which are important N-heterocyclic molecules, have received the consideration of researchers due to their significant biological and pharmaceutical properties
The chemistry used in this paper involves an aqueous diethylamine catalyzed Michael addition of 1,3-dimethylbarbituric acid to nitro-olefins at room temperature for less than 1 h [16] (Scheme 1)
The weight loss pattern of all the compounds was found to be different at different intervals with 1a,b displaying a weight loss of 70% and 98% respectively at 200 °C, but at the same temperature the weight loss percentage for the barbituric acid derivatives 2a,b were found to be 48% and 18 % respectively
Summary
Pyrimidine and its derivatives, which are important N-heterocyclic molecules, have received the consideration of researchers due to their significant biological and pharmaceutical properties. Barbiturates (barbituric acid derivatives) are a class of central nervous system depressants, [10] utilized as sedatives, sleeping agents, hypnotics, anxiolytics, anticonvulsants, and anesthetics [7] They have additional pharmacological activities as antioxidant anxiolitics, analeptics, anti-AIDA, immunomodulatory, anticancer agents and in other psychiatric disorders, and possess effects on motor and sensory functions [11,12,13,14,15] For example, phenobarbital, a 5-alkylated barbituric acid, was reported to exhibit sedative and hypnotic properties, and most importantly is an anticonvulsant [16]. DFT calculations were undertaken to study the optimized molecular structural parameters, vibrational frequencies, thermodynamic parameters, total dipole moment and HOMO-LUMO energy gap for the synthesized molecules using B3LYP/6-311G(d,p) basis set. The findings of these spectroscopic and theoretical studies are reported
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