Modeling NMR parameters by DFT methods as an aid to the conformational analysis of cis-fused 7a(8a)-methyl octa(hexa)hydrocyclopenta[d][1,3]oxazines and [3,1]benzoxazines

被引:109
作者
Tähtinen, P
Bagno, A
Klika, KD
Pihlaja, K
机构
[1] Univ Turku, Dept Chem, Struct Chem Grp, FIN-20014 Turku, Finland
[2] Univ Padua, Dipartimento Chim Organ, CNR, Ctr Meccanismi Reaz Organ, ITA-35131 Padua, Italy
关键词
D O I
10.1021/ja021237t
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The energies of the preferred conformations of four 7a-methyl octa(or hexa)hydrocyclopenta[d][1,3]-oxazines, five 8a-methyl octa(or hexa)hydro[3,1]benzoxazines, and 8a-methyl hexahydro[1,3]benzoxazinone, all cis-fused, were investigated by DFT methods. Following geometry optimization at the B3LYP/6-31 G(d,p) level, both the proton chemical shifts and the vicinal coupling constants between H-4a and the H-4 and H-5 protons were calculated at the B3LYP/cc-pVTZ level and compared to the previously experimentally measured values. The agreement between the calculated and the experimental chemical shifts was found to be good. Similarly, the agreement between the calculated and the experimental vicinal coupling constants was also found to be good, thus providing a methodology for determining the conformational equilibria of such systems that is comparable in many respects to experimental approaches such as variable-temperature NMR or to the use of model coupling constant values, when available, from analogous compounds.
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页码:4609 / 4618
页数:10
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