Stereoselectivity of triplet photocycloadditions: Diene-carbonyl reactions and solvent effects

被引:64
作者
Griesbeck, AG [1 ]
Buhr, S [1 ]
Fiege, M [1 ]
Schmickler, H [1 ]
Lex, J [1 ]
机构
[1] Univ Cologne, Inst Organ Chem, D-50939 Cologne, Germany
关键词
D O I
10.1021/jo971767l
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
The diastereoselectivity of the photocycloaddition of benzaldehyde to furan was determined (exo/endo = 212:1) and compared with the reaction of other carbonyl compounds and carbonyl analogues. These results were compared with Paterno-Buchi reactions of cycloalkenes and cyclic enol ethers. An increase in steric demand of the a-substituent in benzoyl compounds led to a change in exo/endo-selectivity for furan cycloadditions that was not observed for cycloalkenes or cyclic enol ethers. Different ISC-reactive conformers with enhanced spin-orbit coupling are postulated as a reasonable explanation for the stereoselectivities observed. Additionally, solvent effects were studied, demonstrating the influence of photoinduced electron-transfer steps on the regio- and diastereoselectivity of Paterno-Buchi reactions with 2,3-dihydrofuran in polar solvents. Two bicyclic oxetanes (8 and 10) were characterized by X-ray structure analysis.
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页码:3847 / 3854
页数:8
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