Fluorescence behaviour and photochemical reactivities of 2-pyridones.

Regioselective photocycloadditions of 2‐pyridones (1) with 2,4‐pentadienoates (3) were analysed and compared with the reactions with propenoate (2), and origins of the different regioselectivities were inferred from frontier molecular orbital properties by the use of PM3‐CI method. Direct photoreactions of 1 with 3 being α,β,γ,δ‐unsaturated carboxylates gave four types of regio‐selective [2+2]cycloadducts, 3‐β:4‐α‐4, 5, 3‐δ:4‐γ‐6,7,5‐δ: 6‐γ‐8, 9 and 5‐δ:6‐γ‐[2+2]cycloadducts 10,11. Sensitized photoreactions of 1 with 3 did not occur, and fluorescence of 1 was weakly quenched by 3. Otherwise, main cycloadducts in the sensitized reactions of 1 with 2 have been obtained as 5‐α:6‐β‐[2+2]cycloadducts, which were different from main 3‐β:4‐α‐[2+2]cycloadducts of the direct reactions, and these site‐and regio‐selectivities were inferred from the different frontier molecular orbital coefficients at the. 3‐and 6‐positions of 1 for the triplet and singlet states. Formations of 4–7 were also interpreted by both effects of frontier orbital HSOMO‐LUMO interactions and of the electrostatic interaction between 1 and 3. The other site‐and regioselective adducts 8–11 were inferred to be formed by the electrostatic interactions similar to 2‐pyridone photodimerization.

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Singlet and triplet photocycloaddition reactions of 2‐pyridones with propenoate and 2,4‐pentadienotes, and the frontier molecular orbital analysis

Suishu

Shimo

Somekawa

1997

Journal of Heterocyclic Chem

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Substituent effects on the regiochemistry of enone-alkene 2+2-photocycloadditions. Experimental results and FMO analysis

1997

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Theoretical Approach to [2+2] Excited Cyclic Reaction between 2-Pyridone and Methylacrylate through Conical Intersections

Sakai

Yada

Ito

2017

Bulletin of the Chemical Society of Japan

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The [2+2] photocycloaddition of 2-pyridone and methylacrylate through conical intersections was studied using ab initio molecular orbital (MO) methods. For the cyclic addition of 2-pyridone and methylacrylate, fourteen parallel-type conical intersections were located, which is the same type as that found in ethylene dimers. CiLC (CI/LMO/CASSCF) analysis of the conical intersections indicated that the ratio of regions proceeding toward products and reactants is nearly the same for all parallel-type conical intersections. These intersections are energetically located below the excited state of 2-pyridone and methylacrylate, and the order of the energies of the parallel type conical intersections corresponds to the quantity of products obtained experimentally. The regioselectivity of the photocycloaddition was explained from the conformation of the parallel type conical intersections with polarization.

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Fluorescence behaviour and photochemical reactivities of 2-pyridones.

Cited by 6 publications

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Singlet and triplet photocycloaddition reactions of 2‐pyridones with propenoate and 2,4‐pentadienotes, and the frontier molecular orbital analysis

Singlet and triplet photocycloaddition reactions of 2‐pyridones with propenoate and 2,4‐pentadienotes, and the frontier molecular orbital analysis

Substituent effects on the regiochemistry of enone-alkene 2+2-photocycloadditions. Experimental results and FMO analysis

Theoretical Approach to [2+2] Excited Cyclic Reaction between 2-Pyridone and Methylacrylate through Conical Intersections

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