118465-23-9Relevant academic research and scientific papers
Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
supporting information, p. 8135 - 8148 (2019/05/29)
The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate 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.
Br?nsted Acid Catalysis in Visible-Light-Induced [2+2] Photocycloaddition Reactions of Enone Dithianes
Brenninger, Christoph,P?thig, Alexander,Bach, Thorsten
supporting information, p. 4337 - 4341 (2017/04/04)
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 Br?nsted 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 %). It is also shown that the dithiane moiety can be reductively or oxidatively removed without affecting the photochemically constructed ring skeleton.
Insight into acid-mediated asymmetric spirocyclization in the presence of a chiral diol
Kiguchi,Tsurusaki,Yamada,Aso,Tanaka,Sakai,Suemune
, p. 1536 - 1540 (2007/10/03)
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) th
SOLVOLYSIS OF 3-ALKENYL-2-CYCLOHEXENYL ESTERS
Jursic, Branko,Ladika, Mladen,Bosner, Branka,Kobetic, Renata,Sunko, Dionis E.
, p. 2311 - 2318 (2007/10/02)
In an attempt to study possible ?-participation in allyl-dervatives, 3-alkenyl-5,5-dimethyl-2-cyclohexenyl p-nitrobenzoates 4 and 2-alkenyl-3-methyl-2-cyclohexenyl p-nitrobenzoates 5 were solvolyzed in 97 wt percent trifluoroethanol and 80 vol percent ethanol.Water soluble 1-methyl-3-(3-alkenyl-5,5-dimethyl-2-cyclohexenyl)pyridinium iodides 6 were solvolyzed in water and in aqueous solvents, as well as under micellar conditions.All esters show in each of the solvents normal values of secondary α-deuterium isotope effects (kH/kD = 1.17-1.23).Also in comparison to saturated analogues the investigated esters show a lower solvolytic reactivity.On the basis of these results it was concluded that the solvolysis proceeds via a stepwise mechanism involving a resonance-stabilized cyclohexenyl cation as the reaction intermediate.
