Photochemistry of the phenanthrene-stilbene system. Cycloaddition and singlet-sensitized isomerization

Caldwell, Richard A.; Mizuno, Kazuhiko; Hansen, Poul Erik; VO, L. P.; FRENTRUP, M.; Ho, C.

doi:10.1021/ja00414a037

Cited by 30 publications

(6 citation statements)

References 3 publications

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“…Irradiation of mixtures of 3% 1 and 97% 2 either as thin films or concentrated solutions (0.5 M in benzene) resulted in isomerization of 2 and formation of 3 and 4, but at best trace amounts of a third dimer. The preferential reaction of singlet 1 with ground state 1 vs 2 is consistent with previous reports for the [2+2] cycloaddition reaction of 1 vs 2 with singlet 9-cyanophenanthrene (Caldwell et al, 1981).…”

Section: Resultssupporting

confidence: 92%

Molecular Structure and Photodecarbonylation of 2,3,4,5‐ Tetraphenylcyclopentanone

Lewis

Field

Sabat

1990

Photochem & Photobiology

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Abstract— Clemmensen reduction of tetracyclone yields r‐2,t‐3,t‐4,c‐5‐tetraphenylcyclopentanone, the structure of which was established by x‐ray crystallography. Photodecarbonylation of this molecule results in the formation of cis‐ and trans‐stilbenes and minor amounts of tetraphenykyclobutane. The stilbenes are initially formed in comparable yield, but secondary photoisomerization results in cw‐rich mixtures. Stepwise photodecarbonylation is proposed to yield triplet meso‐ 1,2,3,4‐tetraphenylbutane‐diyl which undergoes nonstereoselective elimination in preference to cyclization. The intermediacyof the same biradical in the photodimerization stilbene can be effectively eliminated on the basis of stereochemical evidence.

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Section: Resultssupporting

confidence: 92%

Molecular Structure and Photodecarbonylation of 2,3,4,5‐ Tetraphenylcyclopentanone

Lewis

Field

Sabat

1990

Photochem & Photobiology

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“…Since the rst report of photochemical [2 + 2] cycloaddition accessing a 4-membered carbocycle by Liebermann in 1877, 6 the construction of 4membered cyclobutyl rings from photo-cycloaddition of alkenes has become arguably the most employed technique for cyclobutanation. [7][8][9][10][11][12] Cyclobutanation can now also be readily achieved via organocatalysis, [13][14][15] organometallic catalysis, 7,[16][17][18] as well as electrocatalysis [19][20][21][22] (Scheme 1). Until recently when the synthesis of substituted cyclobutanes could be realised via selective C-H functionalisation of unsubstituted cyclobutanes, [23][24][25][26] formal [2 + 2] cycloaddition remained the main strategy for the synthesis of complex, tetra-substituted cyclobutyl rings.…”

Section: Introductionmentioning

confidence: 99%

Stereoretention in styrene heterodimerisation promoted by one-electron oxidants

Zhang

Paton

2020

Chem. Sci.

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“…Since the first report of photochemical [2+2] cycloaddition accessing a 4membered carbocycle by Liebermann in 1877, 6 the construction of 4-membered cyclobutyl rings from photo-cycloaddition of alkenes have become arguably the most employed technique for cyclobutanation. [7][8][9][10][11][12] Cyclobutanation can now also be readily achieved via organocatalysis, [13][14][15] organometallic catalysis, 7,[16][17][18] as well as electrocatalysis [19][20][21][22] (Scheme 1). Until recently when the synthesis of substituted cyclobutanes could be realised via selective C-H functionalisation of unsubstituted cyclobutanes, [23][24][25][26] formal [2+2] cycloaddition remains the main strategy for the synthesis of complex, tetra-substituted cyclobutyl rings.…”

Section: Introductionmentioning

confidence: 99%

Stereoretention in Styrene Heterodimerisation Promoted by One-Electron Oxidants

Zhang

Paton²

2020

Preprint

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Radical cations generated from the oxidation of C=C p-bonds are synthetically useful reactive intermediates for C–C and C–X bond formation. Radical cation formation, induced by sub-stoichiometric amounts of external oxidant, are important intermediates in the Woodward-Hoffmann thermally disallowed [2+2] cycloaddition of electron-rich alkenes. Using density functional theory (DFT), we report the detailed mechanisms underlying the intermolecular heterodimerisation of anethole and β-methylstyrene to give unsymmetrical, tetra-substituted cyclobutanes. Reactions between trans-alkenes favour the all-trans adduct, resulting from a kinetic preference for anti-addition reinforced by reversibility at ambient temperatures since this is also the thermodynamic product; on the other hand, reactions between a trans-alkene and a cis-alkene favour syn-addition, while exocyclic rotation in the acyclic radical cation intermediate is also possible since C-C forming barriers are higher. Computations are consistent with the experimental observation that hexafluoroisopropanol (HFIP) is a better solvent than acetonitrile, in part due to its ability to stabilize the reduced form of the hypervalent iodine initiator by hydrogen bonding, but also through the stabilisation of radical cationic intermediates along the reaction coordinate.

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Photochemistry of the phenanthrene-stilbene system. Cycloaddition and singlet-sensitized isomerization

Cited by 30 publications

References 3 publications

Molecular Structure and Photodecarbonylation of 2,3,4,5‐ Tetraphenylcyclopentanone

Molecular Structure and Photodecarbonylation of 2,3,4,5‐ Tetraphenylcyclopentanone

Stereoretention in styrene heterodimerisation promoted by one-electron oxidants

Stereoretention in Styrene Heterodimerisation Promoted by One-Electron Oxidants

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