ISSN:
0009-2940
Keywords:
Enol lactones, photochemistry of / Ketene photoextrusion / Ketones, photoreduction / 0-Heterocycles, photochemistry of
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photochemical conversion of 4,4,7,7-tetramethyl-4,6,7,8-tetrahydro-2H-benzopyran-2,5(3H)-dione (1) into 3,3,6,6-tetramethyl-3,5,6,7-tetrahydrobenzofuran-4(2H)-one (4) in methanol does not - as previously assumed - proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2. This conclusion results from the finding that C-2, i. e. the CH2 group, of benzofuranone 4 stems from the solvent. Similar observations were made for other benzopyrandiones 15. A reaction sequence consisting of (a) ketene elimination from 2 with formation of 2-isopropylidene-5,5-dimethyl-1,3-cyclo-hexanedione and (b) light-induced (reductive) H . and . CH2OH addition to this intermediate followed by cyclization and dehydration to 4, is proposed for the conversion 1→4.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901230121
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