The global electrophilicity index ω 8 ( ω = μ 2/2 η ) measures the stabilization energy in the process of getting an additional electronic charge ΔN from the environment. 7įrom recent DFT studies it has been evidenced that global and local electrophilicity parameters are important tools for predicting the feasibility, polar character and mechanistic aspects of Diels-Alder reaction. The results were in excellent correlation with the experimental findings reported by Bogdanowicz et al. Furthermore, the regioselectivity of cycloaddition reaction was also predicted in view of local electrophilicity and nucleophilicity descriptors. 7, we have explored these parameters for the 1-(2-furyl)-3-(dimethylamino)-2-propene-1-thione (diene) and various dienophiles and predicted the behavior of Diels-Alder reaction to afford 2-furyl substituted 2H-thiopyrans. Therefore, keeping in view the importance of global and local reactivity descriptors, and in continuation of the work of Bogdanowicz et al. 29-33 Thus exploration of global and local reactivity descriptors to understand the mechanistic aspects for a cycloaddition reaction is worth important. 21-28 Moreover, recent literature study reveals that global and local descriptors are very useful and reliable tools for the predication of reaction mechanisms. In this context, for a long time, Domingo's group has been involved in the study of the DA reactions using these parameters to establish the polar character of cycloaddition. Moreover, the local reactivity descriptors provide a deep insight about the regioselectivity of cycloaddition reactions. Fukui function and local electrophilicity/nucleophilicity are extensively applied to probe the local reactivity and site selectivity. In this regards global electrophilicity, 8 chemical potential, 9-10 global hardness, 11-16 global softness, 10,17 and nucleophilicity 18-20 are highly successful in predicting the feasibility and polarity of cycloaddition reactions. Global and local reactivity descriptors evaluated using DFT are very much useful in explaining the behavior of reactant and products in an organic reaction. In this context, several reactivity descriptors have been proposed and used to analyze chemical reactivity and site selectivity. 7, has studied the Diels-Alder reaction of 2-furyl substituted 1-thia-1, 3-butadiene with various electrophilic olefins affording 2-furyl substituted 2H-thiopyran derivatives with high stereo selectivity.ĭensity functional theory (DFT) has been quite successful in explaining theoretical background of molecular properties and chemical concepts. Among these compounds the study of the behavior of carbon chalcogen double bonds (-C=S, -C=O, -C=Se) as dienes in hetero-Diels-Alder (HDA) reaction is worth important. In recent years, the chemistry of multiple bond compounds is quite interesting. Hetero-Diels-Alder reactions are the most powerful available methodologies for the construction of six membered heterocyclic derivatives which have wide applications in the area of medicinal, computational and synthesis. Keywords: Enaminothione, DFT, B3LYP-6-31G*, global and local reactivity descriptors These outcomes were found to be in exact correlation with the experimental outcomes achieved by Bogdanowicz et al. Regional nucleophilicity at the interacting site of diene were evaluated using local nucleophilicity descriptor N k. However, unsymmetrical dienophiles 16,18a-e and 21 have shown a preference towards a particular regioisomer and shown high regioselectivity during cycloaddition reaction. For symmetrical dienophiles viz., 2, 5, 8, 11a, 11b, 13 and 14 the local descriptors concentrates equally (50%) at both interacting sites, to allocate non-regioselective cycloadditions. The local descriptors based on Parr functions proposed by Domingo were found to be quite promising to explain the regioselectivity of cycloaddition processes. The results preluded that the polarity and charge transfer flow between diene and dienophiles was consistent with the global reactivity descriptors and substitutional pattern. * e-mail: mechanism of the Diels-Alder reaction of 1-(2-furyl)-3-(dimethylamino)-2-propene-1-thione with various dienophiles resulting in the formation of 2H-thiopyran derivatives were discussed by evaluating global and local electrophilicity and nucleophilicity descriptors for whole series of diene and dienophiles at B3LYP/6-31G* level of theory. VINITA SAHU, *,† PRATIBHA SHARMA, ‡ ASHOK KUMAR ‡ĭepartment of Chemistry, Alliance College of Engineering and Design, Alliance University, Bangalore, Karnataka, India IMPACT OF GLOBAL AND LOCAL REACTIVITY DESCRIPTORS ON THE HETERO-DIELS-ALDER REACTION OF ENAMINOTHIONE WITH VARIOUS ELECTROPHILES
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