21876-87-9Relevant articles and documents
STRUCTURE DETERMINATION OF PHOTOCYCLODIMERS OF 2-CYCLOALKENONES VIA ENANTIOSELECTIVE GAS CHROMATOGRAPHY AND GC/MS ANALYSIS
Anklam, Elke,Koenig, Wilfried A.,Margaretha, Paul
, p. 5851 - 5854 (1983)
Enantioselective gas chromatography combined with GC/MS analysis allows the direct assignment of constitution and configuration of the photocyclodimers of cyclic enones 1a - 1h.
Stereoselectivity in Photocycloaddition Reactions, 5.- Photoreaction of 2-Cyclopenten-1-one with Enol Ethers
Griesbeck, Axel G.,Stadtmueller, Stefan,Busse, Holger,Bringmann, Gerhard,Buddrus, Joachim
, p. 933 - 940 (2007/10/02)
The regio- and stereoselectivity of photocycloaddition reactions between 2-cyclopenten-1-one (1) and the electron-rich alkenes: ethyl, isopropyl, and phenyl vinyl ether (2-4) as well as 2,3-dihydrofuran (10) were examined.In all cases the annulated cyclobutene derivatives 5-7 and 11 were isolated in yieldsbetween 70 and 99percent.The regioisomeric HT/HH products were formed in a ratio of 3:1 to 4:1.For the determination of the product stereochemistry, INADEQUATE and 1H,1H-decoupling experiments were performed.Computer-assisted investigations on the molecular geometry and 1H,1H coupling constants were performed by using semiempirical methods (AM1, FINITE).The HT regioisomers were formed with moderate endo diastereoselectivity, whereas in the case of the HH regioisomers both diastereomers (exo/endo) were formed in equal amounts.Photoreaction with 2,3-dihydrofuran (10) led to almost exclusive formation of exo-diastereomeric HH and HT regioisomers 11.The observed stereoselectivity is rationalized by the optimal geometry of the intermediate triplet 1,4-biradicals during intersystem crossing. Key Words: Photocycloaddition / Selectivity, stereo-, regio- / 1,4-Biradicals / INADEQUATE / Calculations, AM1, FINITE
Electrophilic Opening of Photochemically Generated Bicyclopentane Derivatives - A Two-Step 3,3-Dimethylcyclopentane Anellation
Misslitz, Ulf,Primke, Hartmut,Meijere, Armin de
, p. 537 - 544 (2007/10/02)
Tricyclic compounds 7a-e with 5,5-dimethylbicyclopentane subunits were obtained - although in poor yields - by photochemically initiated cycloaddition of 3,3-dimethylcyclopropene to 2-cycloalken-1-ones 4a-e.Catalytic hydrogenation of bicyclopentanes 7a/7c proceeded regioselectively to give bicyclic compounds 17a/17c with gem-dimethyl-substituted cyclopentane units.Treatment of carbonyl-protected bicyclopentanes 16a/16c with mercury(II) acetate in THF/water or THF/methanol followed by reductive demercuration afforded - with practically quantitative diastereo-, but no recognizable regioselectivity - gem-dimethyl-substituted hydroxy- or methoxycyclopentanes 18-21, respectively.Upon warming under reflux the hydroxymercurated ketone 7c gave the regioselectively formed β-elimination product endo-7-hydroxy-8,8-dimethylbicyclonon-1(9)-en-2-one (23).Upon analogous treatment, however, hydroxymercurated 7a was recovered unchanged. - Keywords: Cycloaddition of 3,3-dimethylcyclopropene/ Ring-anellated bicyclopentanes/ Hydroxymercuration of bicyclopentanes/ 3,3-Dimethylcyclopentane anellation
