ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Photochemistry of 5,6-Epoxydienes and of Conjugated 5,6-EpoxytrienesOn singulet excitation (δ = 254 nm) the 5,6-epoxydiene 6 and the conjugated 5,6-epoxytrienes 7 and 8 exclusively give products arising from cleavage of the C, C-bond of the oxirane (cf. 6→9, 10, 11; 7→ (E)-15, 16, 17; 8→ 18 (A+B), 19 (A+B), 20, 21). The dihydrofuran compounds 11 and (E/Z)-15 are formed by cyclization of a ketonium-ylide a and d, respectively. Photolysis of a gives the carbene b which yields the cyclopropene 9, whereas d forms photochemically the carbenes f and g which yield the methano compounds 16 and 17. The isomeric cyclopropene derivatives 20 and 21 are products of the intermediates h and i, respectively, which are formed by photolysis of the ylide e. The cyclopropene 21 isomerizes by intramolecular cycloadditions to 18 (A+B) and 19 (A+B). - On triplet excitation (λ≥LD nm; 280 nm; acetone) 6 undergoes cleavage of the C(5), O-bond and isomerizes to 12 and 14. However, 7 is converted by cleavage of the C, C-bond of the oxirane to yield 15. On treatment with BF3O(C2H5)2 6 gives 14, whereas 7 yields 22, and 8 forms 23 and 24.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19810640122
