ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Compounds of the 3,4-dihydro-ionone series as models for the photochemistry of γ, δ- and δ,∊- unsaturated ketones and aldehydes.The photochemistry of γ, δ- and δ,∊-unsaturated carbonyl compounds of the dihydro-ionone series has been studied, with special attention to the investigation of oxetane formation versus hydrogen abstraction.UV.-irradiation of the dihydro-β-ionone compounds with structure A (1, 7, 14, 18, 24, 29) led to isomeric ethers with structures B (2, 8, 15, 19, 25, 30), C (3, 9, 16, 20, 26, 31) and D (4, 21, 27), isomeric bicyclic alcohols with structure E (5, 10, 17, 22, 28), and photoreduction products with structure F (6, 11, 12, 13). Photolysis of dihydro-γ-ionone (32) gave a complex mixture containing fragmentation product 35, hydrocarbon 36, β-ambrinol (34), oxetane 33, as well as dihydro-β-ionone (1) and three of its photoproducts (2, 3, 5). The dihydro-α-ionone compounds 37 and 40 gave mixtures of fragmentation products and the oxetanes 38 and 41. Irradiation of the side-chain homologues 42 and 45 yielded 43, which photo-cyclizes to 44. In contrast, 3, 4-dihydro-3′,4′-dehydro-β-ionone (46) gave merely the isomeric open-chain triene-ketone 47.The structures assigned to the ethers 2, 3, 33, 38 and to the alcohols 5, 10, 13 could be confirmed by chemical reactions and mutual interconversions. The structure of the ether 21 had to be established by X-ray analysis, details of which are described.A novel intramolecular hydrogen transfer is involved in formation of ethers B. The photocyclization A → D probably proceeds by addition of the carbonyl-C atom to the double bond (A → h), followed by methyl (1 → 2)-shift (h → i). Process A → h may also be involved in formation of compounds of type C and E.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19760590105
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