ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The effect of substituents (X = H, Me, or F at C(6), R = H or Me at C(2′) of the allyl side chain) on the photoisomerization (λ = 350 nm) of 6-allylcyclohex-2-enones 1 in MeCN is studied. Substituents X control the overall efficiency of intramolecular [2 + 2] photocycloadduct formation (Φ: Me 〉 F 〉 H) but do not exercise an influence on the orientation of addition of the exocyclic double bond to the enone C=C bond. In contrast, replacement of the prop-2-enyl (R = H) by a 2-methylprop-2-enyl (R = Me) side chain causes a change in the tricyclo[3.3.1.02,7]nonan-6-one 4 vs. tricyclo[4.2,1.03,8]nonan-7-one (5) product ratio from 100:0 (R = H) to roughly 2:1 (R = Me) but has almost no bearing on the relative rates of conversion of 1 to products. For C(6)-unsubstituted enones 1aa and 1ba (X = H), the efficiency of cyclization becomes low enough so that lumiketone rearrangement to bicyclohexanones 6 and 3-isopropylcyclopent-2-enones 9 becomes competitive. Enones 9 undergo consecutive intramolecular [2 + 2] photocycloaddition to tricyclo[3.2.1.03,6]octan-2-ones 7 and to tricyclo[3.2.1.03,6]octan-7-ones 8, compounds 8 only being formed when R = Me.
Additional Material:
3 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19900730208
Permalink