3-phenyl-2-cyclopentenyl methylketones (15–18, 30, 31) undergo a 1,3-acetyl shift on direct irradiation, and the oxa-di-π-methane rearrangement to photochemically non-interconverting endo and exo bicyclo-[2.1.0]pentyl methylketones on tripletsensitization. Exceptions include the 2-methyl-3-phenyl-2-cyclopentenyl methylketone 32 and the 1-phenyl-2-cyclo-pentenyl methylketone 44 which are unreactive
AlCl<sub>3</sub>-Mediated Aldol Cyclocondensation of 1,6- and 1,7-Diones to Cyclopentene and Cyclohexene Derivatives
作者:Yuji Miyahara、Yoshio N. Ito
DOI:10.1021/jo5006137
日期:2014.8.1
Exactly 1/3 mol of AlCl3 is sufficient to cyclize 1 mol of 1,omega-dibenzoylbutane (or pentane) to a cyclopentenone (or hexenone) derivative in high yield at room temperature in 40 min to several hours. This condensation is driven by removing elements of water as HCl and Al(OH)(3), and the product enones are exclusively unconjugated, unlike the base-catalyzed condensations providing thermodynamically more stable conjugated enones.