The Photochemical 1,3 Addition of Alcohols to Benzenes<sup>1</sup>

Kaplan, Louis; Ritscher, James S.; Wilzbach, K. E.

doi:10.1021/ja00964a067

Cited by 43 publications

(19 citation statements)

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“…Both mechanistic pathways involve relief of the S 1 -state antiaromatic character of benzene, but in different ways. Many pieces of evidence have been acquired for pathway A 31 , 32 and pathway B, 24 , 33 but no previous study has unambiguously confirmed one mechanism over the other. With regard to ESAA relief, any pathway that allows for disruption of the 6π-electron cycle which is antiaromatic in S 1 will provide for such relief.…”

Section: Results and Discussionmentioning

confidence: 99%

“…When irradiated with 254 nm light, benzene rearranges in the S 1 state to benzvalene and fulvene, and when irradiated by light in the range of 165–200 nm, it also forms Dewar benzene. 23 Irradiation of benzene by 254 nm light in nucleophilic solvents leads to derivatives of bicyclo[3.1.0]hexene 1 ( Scheme 1 ), 24 a reaction that was established for 1,3,5-tri- tert -butylbenzene, 24 benzene, 25 and tert -butylbenzene several decades ago. 25 However, the low reaction yields, the long reaction times, and the observed complex mixtures of products are severe drawbacks.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

et al. 2020

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Benzene exhibits a rich photochemistry which can provide access to complex molecular scaffolds that are difficult to access with reactions in the electronic ground state. While benzene is aromatic in its ground state, it is antiaromatic in its lowest ππ* excited states. Herein, we clarify to what extent relief of excited-state antiaromaticity (ESAA) triggers a fundamental benzene photoreaction: the photoinitiated nucleophilic addition of solvent to benzene in acidic media leading to substituted bicyclo[3.1.0]hex-2-enes. The reaction scope was probed experimentally, and it was found that silyl-substituted benzenes provide the most rapid access to bicyclo[3.1.0]hexene derivatives, formed as single isomers with three stereogenic centers in yields up to 75% in one step. Two major mechanism hypotheses, both involving ESAA relief, were explored through quantum chemical calculations and experiments. The first mechanism involves protonation of excited-state benzene and subsequent rearrangement to bicyclo[3.1.0]hexenium cation, trapped by a nucleophile, while the second involves photorearrangement of benzene to benzvalene followed by protonation and nucleophilic addition. Our studies reveal that the second mechanism is operative. We also clarify that similar ESAA relief leads to puckering of S 1 -state silabenzene and pyridinium ion, where the photorearrangement of the latter is of established synthetic utility. Finally, we identified causes for the limitations of the reaction, information that should be valuable in explorations of similar photoreactions. Taken together, we reveal how the ESAA in benzene and 6π-electron heterocycles trigger photochemical distortions that provide access to complex three-dimensional molecular scaffolds from simple reactants.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

et al. 2020

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“…[3]) for benzene-d 6 in 2,2,2-trifluoroethanol (TFE) on photolysis in alcohol solvents (5,6). Research in this area up until 1980 has been the subject of several reviews (7)(8)(9)(10).…”

Section: Introductionmentioning

confidence: 99%

“…The results indicated that these compounds are divided into two independent triads as shown in eqs. [4] and [5]. For instance, photolysis of 9-34 in AN gave only 9-23 and 9-26 (eq.…”

Section: Introductionmentioning

confidence: 99%

Steric effects in the phototransposition reactions of dialkylbenzenes

Gonzalez¹,

Pincock²

2006

Can. J. Chem.

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The photochemistry, photophysical properties, and temperature dependence (-25 to +65°C) of fluorescence by quantum yields and excited singlet state lifetimes in acetonitrile have been examined for three sets of dialkylbenzene derivatives: Set 1 -ortho-xylene (10), tetralin (11), and indan (12); Set 2 -2,3-dimethylbenzonitrile (9-23), 5-cyanotetralin (T-23), and 4-cyanoindan (I-23); and Set 3 -3,4-dimethylbenzonitrile (9-34), 6-cyanotetralin (T-34), and 5-cyanoindan (I-34). Phototransposition reactions occur for 10, 9-23, 9-34, and T-34. Fitting of the temperature-dependent fluorescence data to an Arrhenius expression gave A and E a values for all substrates studied except I-23 and I-34. The fluorescence intensity of these two compounds was essentially independent of temperature. For the other compounds, the data revealed that the activation barrier separating the excited singlet state (S 1 ) from the reactive intermediate, a prefulvene biradical, was the important one in determining the reaction efficiency. The dominant mode of decay of the reactive intermediate was internal return to the starting material. Moreover, the general observation was made that nitrile substitution ortho to one of the alkyl groups in these dialkylbenzene derivatives reduced the rate at which they were converted to the reactive intermediate and, therefore, also the efficiency of the phototransposition reactions.Résumé : En se basant sur les rendements quantiques ainsi que les temps de vie de l'état singulet excité observés lors de réactions dans l'acétonitrile, on a étudié la photochimie, les propriétés photophysiques et la relation entre la tempé-rature (-25 à +65°C) et les rendements quantiques pour trois ensembles de dérivés benzéniques dialkylés, soit l'ensemble 1 formé d'ortho-xylène (10), de tétraline (11) et d'indane (12); l'ensemble 2 formé de 2,3-diméthylben-zonitrile (9-23), de 5-cyanotétraline (T-23) et de 4-cyanoindane (I-23); l'ensemble 3 formé de 3,4-diméthylbenzonitrile (9-34), de 6-cyanotétraline (T-34) et de 5-cyanoindane (I-34). Il se produit des réactions de phototransposition pour les composés 10, 9-23, 9-34 et T-34. Un ajustement des données de fluorescence influencées par la température à une expression d'Arrhenius permet de calculer les valeurs A et E a pour tous les substrats étudiés, à l'exception de I-23 et I-34. L'intensité de la fluorescence de ces deux composés est essentiellement indépendante de la température. Pour les autres composés, les données ont permis de déterminer que la barrière d'activation qui sépare S 1 , l'état singulet excité, de l'intermédiaire réactif, un biradical préfulvène, est celle qui est importante dans la détermination de l'efficacité de la réaction. Le mode dominant dans la désactivation de l'intermédiaire réactif est le retour interne vers le produit de dé-part. De plus, on a observé que la présence d'un substituant nitrile en position ortho par rapport aux groupes alkyles de ces dialkylbenzènes provoque une réduction de la vitesse avec laquelle ils se transforment en intermédiaire...

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“…We are left with a dilemma recently faced by others (27)(28)(29)(30) We explain the isomerization of VII to VIII as proceeding via XXIX. Whether X also intervenes as an intermediate, we…”

Section: Ch3o Co2cd3mentioning

confidence: 99%

Part I: Photoisomerization of tetra-O-methylpurpurogallin and the base catalyzed rearrangement of tri-O-methylpurpurogallin Part II: Oxidations with phenylhydrazines

Murphy

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The Photochemical 1,3 Addition of Alcohols to Benzenes¹

Cited by 43 publications

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Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

Steric effects in the phototransposition reactions of dialkylbenzenes

Part I: Photoisomerization of tetra-O-methylpurpurogallin and the base catalyzed rearrangement of tri-O-methylpurpurogallin Part II: Oxidations with phenylhydrazines

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The Photochemical 1,3 Addition of Alcohols to Benzenes1

Cited by 43 publications

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Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes

Steric effects in the phototransposition reactions of dialkylbenzenes

Part I: Photoisomerization of tetra-O-methylpurpurogallin and the base catalyzed rearrangement of tri-O-methylpurpurogallin Part II: Oxidations with phenylhydrazines

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The Photochemical 1,3 Addition of Alcohols to Benzenes¹