ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The Photochemistry of Conjugated Epoxy-Inones: Photolysis of 5,6-Epoxy-5-isopropyl-6-methyl-hept-3-in-2-onThis paper continues the series of investigations of the photochemistry of α,β-unsaturated γ,δ-epoxyketones by examining the hitherto unknown photochemical behaviour of α,β-acetylenic-γ,δ-epoxy-ketones. As model compound, the aliphatic epoxy-ynone 7 (thermally stable at 180°) was synthesized (Scheme 1). It can be converted with BF3O (C2H5)2 in good yields to the 1,5-diketone 8, the yne-1,4-diketone 49 and in small amounts to the fluorhydrine 50 (Scheme 1).On n,π*- or π, π*-excitation, 7 shows mainly cleavage of the C (γ)-O-bond to give a diradical a (Scheme 11), whose ultimate fate is strongly solvent dependent. In acetonitrile a mainly rearranges to the 1,5-diketone 8 and, to a smaller extent, shows fragmentation to acetone and formation of polymers. Except for small amounts of the dimeric products 9A,9B and biphenyl, the same compounds are obtained in benzene. In cyclopentane, however, a gives only little of 8, and mainly a plethora of compounds formed by a radical process like H-abstraction from solvent, incorporation of cyclopentylradicals, dimerization and fragmentation reactions (9A, 9B, 11-20) (Scheme 3). Irradiation of 7 in propan-2-ol or in dioxane yields products of analogous radical processes as well of photoreduction (Scheme 4). However, the analogous epoxyenone 32 gives mainly products of photoisomerizations without interference by the solvent [6].On photochemical excitation in acetonitrile, the 1,5-diketone 8 shows unspecific decomposition, but in cyclopentane it yields the reduction products 12, 26A, 26B, 27, 28 plus cyclopentylcyclopentane (15) (Scheme 6).
Additional Material:
3 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19770600308
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