ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Cycloadditions of 3,4-dimethoxyfuran with benzoquinonesCycloaddition of 3,4-dimethoxyfuran (3,4-DF, 1) with 1,4-benzoquinones furnishes isolable (2 + 4)-adducts in high yield. The crystalline products with benzoquinone, 2-methyl-benzoquinone, 2,3-dimethoxy-benzoquinone have endo-configuration, whereas 2,3-dimethyl-benzoquinone gives the exo-adduct 4c exclusively. Halogens (Cl2, Br2) add rapidly across the highly nucleophilic double bond of 3 or 4 in stereospecific cis-manner, and exclusively from the exo-side. The product 5c shows no sign of enolization to the hydroquinone; but with 3a and 3d the hydroquinones 6 were found. Methanolysis of 5 leads to the stable acetals 7 and 8. On oxidation of the hydroquinones 7 the thermolabile quinones 10 were obtained. Preparative pyrolysis of 10a under relatively mild conditions (N2, 200°, 0.1 Torr) gives tetramethoxy ethene (11) and isobenzofuran-4,7-quinone 12, a yellowish, crystalline and stable compound.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19790620718
Permalink