that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)‐italicene
Asymmetric spirocyclization based on intramolecular conjugate addition using a combination of a Lewis acid and an optically active cyclohexane-1, 2-diol has been studied in connection with 1) the effect of substituents on the cyclohexane-1, 2-diol and 2) the effect of substituents on the substrate. This reaction was found to be both thermodynamically and kinetically controlled under restricted conditions.
1,3-Dithiane-protected enones (enone dithianes) were found to undergo an intramolecular [2+2] photocycloaddition under visible-light irradiation (λ=405 nm) in the presence of a Brønsted acid (7.5-10 mol %). Key to the success of the reaction is presumably the formation of colored thionium ions, which are intermediates of the catalytic cycle. Cyclobutanes were thus obtained in very good yields (78-90 %)
AlCl<sub>3</sub>‐Promoted Conia‐Ene‐Related Cyclization of α,ω‐Diethylenic Ketones and 1,2‐ or 1,3‐Hydroalkenylation of Unactivated Cyclopropanes
作者:Julien Coulomb
DOI:10.1002/adsc.202300317
日期:2023.9.5
α,β-Unsaturated enones possessing an unactivated olefin at the ϵ-, ζ- or η-position underwent an aluminum chloride-promoted Conia-ene-related cyclization, affording unsaturated decalones or hexahydroindenones in generally good yields. Cyclopropanes could be used as olefin surrogates in this process, leading to the same bicyclic products in slightly improved efficiency as the result of 1,2- or 1,3-hydroalkenylation