Molecular photochemistry. XXIV. Photocycloaddition of acetone to 1,2-dicyanoethylene

Dalton, J. Christopher; Wriede, Peter A.; Turro, Nicholas J.

doi:10.1021/ja00708a035

Cited by 73 publications

(20 citation statements)

References 3 publications

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“…Besides the photocycloaddition of acetone to olefins leading to oxetanes through a singlet pathway, the photosensitized dimerization of olefins also occurs through an excitation energy transfer from triplet acetone to the olefin 10. In addition, the reactions of excited acetone with olefins can lead to cycloaddition to oxetane and cis–trans isomerization of olefins via a 1,4‐biradical intermediate11a or through triplet energy transfer 11b. These studies focused on the mechanisms of the photocycloaddition and cis–trans isomerization between excited acetone and olefins, but no attention was paid to the factors controlling these competitive reactions, that is, the PB reaction versus sensitized dimerization and the PB reaction versus cis–trans isomerization, and their kinetics.…”

Section: Resultsmentioning

confidence: 99%

Regioselectivity and Competition of the Paternò–Büchi Reaction and Triplet–Triplet Energy Transfer between Triplet Benzophenones and Pyrimidines: Control by Triplet Energy Levels

Liu

Wang

Tong

et al. 2013

Chemistry A European J

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The photochemical reaction of a pyrimidine and a ketone occurs either as a Paternò-Büchi (PB) reaction or as energy transfer (ET) from the triplet ketone to the pyrimidine. It is rare for the two types of reactions to occur concurrently, and their competitive mechanism remains unknown. In this work, two classes of products, regioisomeric oxetane(s) (2, 3) from a PB reaction and three isomeric dimers of 5-fluoro-1,3-dimethyl uracil (FDMU) (4-6) from a photosensitized dimerization of FDMU, are obtained through the UV irradiation of FDMU with various benzophenones (BPs). The ratio of the two products (oxetanes to dimers) reveals that the two competitive reactions depend strongly on the triplet energy levels (ET ) of the BPs. The BPs with higher ET values lead to higher proportions of dimers, whereas those with lower ET values give higher proportions of oxetane(s), with the generation of just two regioisomeric oxetanes for the BP with the lowest ET of the eight BPs investigated. The ratio of the two oxetanes (2:3) decreases with the BP ET value. The competitive mechanism for the two types of photochemical reactions is demonstrated through quenching experiments and investigation of temperature effects. Kinetic analysis shows that the rate constants of the two [2+2] photocycloadditions are comparable. Furthermore, in combination with the results of previous studies, we have gained insight into the dependence of the photochemical type and the regioselectivity in the PB reaction on the triplet energy gaps (ΔE) between the pyrimidines and ketones. For ketones with higher ET values than the pyrimidines, the photochemical reaction is a photosensitized dimerization of the pyrimidine. In the opposite case, a PB reaction occurs, and the lower the ET of the ketones, the lower the ratio of oxetanes (2:3). When the ET of values of the ketones are close to those of the pyrimidines, the two reactions occur concurrently, and the higher the ET of the ketones, the higher the proportion of the dimers. The ratio of oxetanes (2:3) decreases with the ET value of the BPs.

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Section: Resultsmentioning

confidence: 99%

Regioselectivity and Competition of the Paternò–Büchi Reaction and Triplet–Triplet Energy Transfer between Triplet Benzophenones and Pyrimidines: Control by Triplet Energy Levels

Liu

Wang

Tong

et al. 2013

Chemistry A European J

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“…[14][15][16] Most investigators interpreted that carbon oxygen single bond could form between acetone and electron-deficient double bonds and subsequently acetone recovered as a result of the cleavage of C-O bond in the photo-catalysis process. [17][18][19][20] The benzyl carbon in component 5 is electron-deficient with the interaction of carbonyl and the oxygen atom. Based on these facts, we speculate here that the conversion of 5 into 2a presumably involved in the photo-catalysed ring-opening process by attack of singlet acetone on benzyl carbon and subsequently the acetone is regenerated by photolytic cleavage of the C-O bond.…”

Section: Resultsmentioning

confidence: 99%

The Photochemical Synthesis of N-arylacetyl Lactams

Jiang

Qiu

2013

Journal of Chemical Research

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“…It was known that the triplets of butyrophenone (E, = 72 kcal mol-I), acetone (ET = 78-80 kcal mol-I), and benzophenone (ET = 68 kcal mol-I) were quenched at the diffusion controlled rate by fumaronitrile and so these results at least establish an upper limit for the triplet energy of this isomer (18,19). It was also known that irradiation of ketones with a triplet energy that of biacetyl (ET = 55 kcal mol-I) and fluoren-9-one (ET = 53 kcal mol-I) could lead to some isomerization of fumaronitrile but the photostationary state was not reported and there was no mention of the efficiency of these isomerizations (1 8).…”

Section: The Triplet Energy Of Fumaro-and Maieonitriiementioning

confidence: 93%

Electronic excited states of small ring compounds. VII. Bicyclo[2.1.0]pentanes by the photocycloaddition of 1,2,3-triphenylcyclopropene to fumaro- and maleonitrile

Wong¹,

Arnold²

1979

Can. J. Chem.

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. Can. J. Chem. 57, 1037 (1979). Irradiation of the charge-transfer complex between 1,2,3-triphenylcyclopropene (1) and fumaronitrile (7) and maleonitrile (8) leads to formation of bicyclo[2.1 .O]pentane cycloaddition products (9, 10, 11) and the photoene product (12). These products were also formed when the reaction was photosensitized (triplet-triplet transfer). The structure of the adducts was established by analysis of 13C and 'Hmr spectra. Nuclear Overhauser effect studies were also useful. The triplet energies of 7 and 8 (ET ca. 50 kcal mol-l) were determined by studying the photosensitized isomerization as a function of sensitizer triplet energy. The thermal stability of the new bicyclo[2.1 .O]pentanes has been studied, particularly with regard to the isomerization resulting from cleavage of the central [0] bond in these strained systems. The mechanism of the photocycloaddition reactions is discussed. Chem. 57,1037Chem. 57, (1979. L'irradiation du complexe de transfert de charge entre le triphenyl-1,2,3 cyclopropkne (1) et le fumaronitrile (7) et le maleonitrile (8) conduit a la formation de produits de cycloaddition bicyclo[2.1.0]pentane (9, 10, 11) et du produit (12) photoene. Ces produits se forment aussi lorsque la reaction est photosensibilisee (transfert triplet-triplet). On a determine la structure des adduits g r k e a une analyse des spectres rmn 13C et lH. Des etudes d'effet Overhauser nuclCaire se sont aussi avCrBes utiles. On a determint les Bnergies triplet de 7 et de 8 (ET ca. 50 kcal/mol) en etudiant I'isomCrisation photosensibilisCe en fonction de l'energie du sensibilisateur triplet. On a CtudiB la stabilitk thermique des nouveaux bicyclo[2.1.O]pentanes en particulier en ce qui a trait a I'isom6risation resultant du clivage de la liaison [0] centrale de ces systemes tendus. On discute du mecanisme des reactions de photocycloaddition.[Traduit par le journal] IntroductioliWe have previously reported (lb,c) that the direct irradiation of the charge-transfer complex between 1,2,3-triphenylcyclopropene (1) and dimethyl fuma-

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Molecular photochemistry. XXIV. Photocycloaddition of acetone to 1,2-dicyanoethylene

Cited by 73 publications

References 3 publications

Regioselectivity and Competition of the Paternò–Büchi Reaction and Triplet–Triplet Energy Transfer between Triplet Benzophenones and Pyrimidines: Control by Triplet Energy Levels

Regioselectivity and Competition of the Paternò–Büchi Reaction and Triplet–Triplet Energy Transfer between Triplet Benzophenones and Pyrimidines: Control by Triplet Energy Levels

The Photochemical Synthesis of N-arylacetyl Lactams

Electronic excited states of small ring compounds. VII. Bicyclo[2.1.0]pentanes by the photocycloaddition of 1,2,3-triphenylcyclopropene to fumaro- and maleonitrile

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