Asymmetric spirocyclization: A new type of acid-catalyzed intramolecular 1, 4-addition to form carba-spirocyclic compounds
摘要:
Novel spirocyclization based on intramolecular 1,4-addition and its asymmetric version have been developed using a combination of Lewis acid and 1,2-diol. Treatment of five- and six-membered alpha,beta-unsaturated cyclic ketones having a 4-oxopentyl group at the beta-position with Lewis acid and ethylene glycol gave spiro[4.5]decane-2,7-dione and spiro[5.5]undecane-2,8-dione, respectively. The asymmetric version of this reaction has been developed by using optically active 1,2-diol such as cyclohexane-1,2-diol to afford the spirocyclic products of up to 85% e.e. (C) 1998 Elsevier Science Ltd. All rights reserved.
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
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 %)
The vinylogous conia rearrangement: A masked ene reaction
作者:Andrew S Kende、Ronald C Newbold
DOI:10.1016/s0040-4039(00)99352-3
日期:1989.1
A novel carbocyclic thermal rearrangement of 4-substituted 2-cyclohexen-1-ones is suggested to involve a 'masked' ene reaction and provides a facile route to spirocyclic cyclohexenone systems.
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