ISSN:
1434-193X
Schlagwort(e):
Free radicals
;
Stereoselective addition
;
Chiral 1,3-dioxin-4-ones
;
Photoreactions
;
Spirocycles
;
Chemistry
;
General Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
-Intermolecular addition of radicals to the 1,3-dioxin-4-ones 1a,b and 2a,b with (-)-menthone incorporated as chiral auxiliary in 2-position were investigated. Photochemically generated radicals from 1,3-dioxolane, oxolane, and 2-propanol were added with high facial selectivity from the more exposed a-side. Intramolecular addition of 1,3-dioxolan-2-yl radicals to chiral dioxinones proceeded less efficiently and with lower selectivity also from the a-side. Nevertheless, it was possible to form the new spirocyclic compounds 22-27. The 1,3-dioxin-4-ones 32a,b possessing an unsaturated side chain were attacked by radicals at the terminal double bond. In the case of irradiation of 32b in 1,3-dioxolane a cyclization followed the intermolecular addition of a 1,3-dioxolan-2-yl radical and the dispiro compound 36 was formed. However, the formation of dispiro compound 40 required two reaction steps starting with irradiation of 32b and bromotrichloromethane. The achiral 1,3-dioxin-4-one 44 possessing an unsaturated side chain at C-2 was attacked by 1,3-dioxolan-2-yl radicals preferentially at C-6.
Zusätzliches Material:
6 Ill.
Materialart:
Digitale Medien
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