86840-58-6Relevant 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
, 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
, 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.
Regiochemistry and Stereochemistry of Intramolecular Photocycloaddition of Carbon-Carbon Double Bonds to Cyclohexenones
Becker, D.,Nagler, M.,Sahali, Y.,Haddad, N.
, p. 4537 - 4543 (2007/10/02)
The intramolecular photocycloaddition mechanism of alkenes tethered by a three-methylene chain to cyclohexenones has been studied.It was found that the reversion from a 1,4-diradical intermediate to starting material is slow relative to the rate of photoadduct formation.Only "straight" closure was observed in the systems studied.For compounds 1-3 and 5, the assumption that the first bond is formed between the β-carbon of the enone and C-4' leading to a 1,4-diradical is supported.For the formation of compounds 6-11, possible mechanisms are discussed.
