Determination of the configuration in six-membered saturated heterocycles (N,P, S,Se) and their oxidation products using experimental and calculated NMR chemical shifts |
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Authors: | Miloš Buděšínský Václav Vaněk Martin Dračínský Radek Pohl Lenka Poštová-Slavětínská Vladimír Sychrovský Jan Pícha Ivana Císařová |
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Institution: | 1. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo 2, CZ-166 10 Prague 6, Czech Republic;2. Department of Inorganic Chemistry, Charles University, Hlavova 2040, CZ-128 40 Prague 2, Czech Republic |
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Abstract: | The six-membered saturated heterocycles—4-tert-butyl-1-methylpiperidine, 4-tert-butyl-1-methylphosphine, 4-tert-butyl-tetrahydro-2H-thiopyran, and 4-tert-butyl-tetrahydro-2H-selenopyran—were prepared as suitable model compounds with well-defined geometry for an NMR study of their oxidation products. The corresponding epimeric N-oxides, phosphinoxides, sulfoxides, and selenoxides were obtained by standard chemical preparation and also by in situ oxidation with meta-chloroperbenzoic acid directly in the NMR tube. The experimental 1H and 13C chemical shifts were compared with corresponding calculated data obtained by GIAO approach with DFT, MP2, and HF methods and various basis sets. The correlation of experimental versus calculated data showed the possibility to determine the stereochemistry of the epimeric oxidation products using fast DFT B3LYP/6-31G* method for both geometry optimization and NMR chemical shifts calculation. |
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Keywords: | Six-membered saturated heterocycles (N P S Se) Oxidation products Configuration NMR Quantum chemical calculations X-ray structures |
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