engleski

Chemistry of 1,3-dioxepines. XIII. (E)/(Z) Configurational assignment of 4,7-dihydro-4- hydroxyimino-6-nitro-1,3-dioxepins

The configuration of oximes 1a and 1b was investigated by chemical and spectroscopic methods. Under the Beckmann rearrangement conditions, using sulfonyl chlorides as reagent, the sulfonic esters 2a-c were obtained. Under more drastic condition, using PCl5 or P2O5, the only isolated product was 4-nitro-5H-furan-2-on (3). It was also formed as sole product by hydrolysis of oximes 1a-b, as well as sulfonic ester 2a. The structure of all compounds were determined by one- and two-dimensional homo- and heteronuclear 1H and 13C NMR correlation spectra: COSY, NOESY, HETCOR and HMBC. Gradient selected differential NOE measurements confirmed that in dimethylsulfoxide solution oximes 1a and 1b exist in E-configuration, irrespective of the route of their formation.

1;3-Dioxepins; 4;7-dihydro-4-hydroxyimino-6-nitro-1;3-dioxepins; (E)/(Z) configurational assignment; 1D and 2D NMR spectra; 1H and 13C NMR correlated spectra; differential NOE

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