Original scientific paper

Chemistry of 1,3-Dioxepins. XII.' 4,7-Dihydro-5-nitro-1,3-dioxepins in the Diels-Alder Reaction with 4-Methyloxazole

Milena Jadrijević-Mladar Takač ; Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10000 Zagreb, Croatia
Ivan Butula ; Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10000 Zagreb, Croatia
Mladen Vinković ; PLIVA-Research Institute, Prilaz baruna Filipovića 25, 10000 Zagreb, Croatia
Miljenko Dumić ; PLIVA-Research Institute, Prilaz baruna Filipovića 25, 10000 Zagreb, Croatia

Abstract

4,7-Dihydro-5-nitro-l,3-dioxepins 4' prepared by dehydrohalogenation
of vic-chloronitro-dioxepanes 2 and/or dehydrohalogenationdemercuration of vic-chloromercurynitro-dioxepanes 3 represent reactive dienophiles in the Diels-Alder cycloaddition with 4-methyloxazole (5), giving pyridoxine (8) intermediates 1,5-dihydro-9-hydroxy- 8-methyl-3H-[1,3]dioxepino[5,6-c]pyridines 6 in poor yields. The side products of this reaction were 4,7-dihydro-4-hydroxyimino- 6-nitro-l,3-dioxepins 7, the structure of which was confirmed by parallel synthesis, i.e. by nitrosation of 4 with ethyl nitrite. The order of reactivity in the series of 5-substituted-4, 7-dihydro- 1,3-dioxepins, calculated by AMI semiempirical method, is predicted to be 5-nitro- > 5-unsubstituted- > 5-cyano- > 5-chloro-4,7-dihydro- 1,3-dioxepin, and it is in agreement with experimental data.

Keywords

Hrčak ID:

176964

URI

https://hrcak.srce.hr/176964

Publication date:

1.5.1997.

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