Preparation of Phenanthrenes by Photocyclization of Stilbenes Containing a Tosyl Group on the Central Double Bond. A Versatile Approach to the Synthesis of Phenanthrenes and Phenanthrenoids

Neo, Ana G.; López, Carmen; Romero, Victor; Antelo, Berta; Delamano, José; Serrano, A.; Fernández, Dolores Vilavedra; Almeida, J. F.; Castedo, Luís; Tojo, Gabriel

doi:10.1021/jo100742e

Cited by 32 publications

(13 citation statements)

References 60 publications

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“…Even though examples of tosyloxy involvement in photochemical reactions are limited, the proposed photocyclization leading to the formation of 8 can only be explained through the participation of the tosyloxy group, as a leaving group during the final aromatization/oxidation step (Fig. 14S) [32][33].…”

Section: Resultsmentioning

confidence: 99%

Photochemical Transformations of Chalcone-Vitamin E Hybrids

et al. 2021

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Abstract. Chalcone-vitamin E hybrids 6’-O-tosyl-3,4,5-trimethoxy-δ-tocopherol-chalcone (1), 3,4,5-trimethoxy-δ-tocopherol-chalcone (2), 6’-O-tosyl-3,4,5-trimethoxy-δ-tocopherol-retrochalcone (3) and 3,4,5-trimethoxy-δ-tocopherol-retrochalcone (4) were synthesized as part of a search for new biological activities in these types of derivatives. We report herein on the photoisomerization products of hybrids 1-4, and the effects of the solvent and substitution patterns in producing secondary products such as flavanone 6, 3-deoxyanthocyanidin 8, and hemiketal 10. Photochemically-induced changes are considered important since structural modifications and/or the presence of additional products can affect the biological activity of this type of semisynthetic hybrids. Resumen. Los híbridos de chalcona-vitamina E, 6’-O-tosil-3,4,5-trimetoxi-δ-tocoferol-chalcona (1), 3,4,5-trimetoxi-δ-tocoferol-chalcona (2), 6’-O-tosil-3,4,5-trimetoxi-δ-tocoferol-retrochalcona (3) y 3,4,5-trimetoxi-δ-tocoferol-retrochalcona (4), fueron sintetizados como parte de la búsqueda de nuevos perfiles de actividad biológica para este tipo de derivados. En este trabajo reportamos los productos de fotoisomerización de los híbridos 1-4, y los efectos del disolvente, así como de distintos patrones de sustitución en la generación de productos secundarios como la flavanona 6, la 3-deoxiantocianidina 8, y el hemicetal 10. Los cambios fotoinducidos son considerados de gran importancia debido a que la modificación en la estructura y/o la presencia de productos adicionales puede afectar la actividad biológica de este tipo de híbridos semisintéticos.

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Section: Resultsmentioning

confidence: 99%

Photochemical Transformations of Chalcone-Vitamin E Hybrids

et al. 2021

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“…Thus, P 1 is formed through a UV-promoted stilbene-type electrocyclic reaction with the formation of a 6-membered ring system that, in the presence of oxygen, is irreversibly oxidized to P 2 (Scheme 9). [16][17][18][19][20][21] The experiment was repeated in degassed toluene solution. 3 a was anew converted into P 1 (Figure 4b).…”

Section: Structural Elucidation Of Photoproducts P 1 and Pmentioning

confidence: 99%

Synthesis of Vinylnaphthofurans and NMR Analysis of their Photoswitching

et al. 2021

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An easy synthesis of photochromic vinylnaphthofurans by the acid-catalyzed one-pot reaction of naphthols with but-2-yne-1,4-diols is described. These uncolored polyaromatic compounds are activated by UV light, at room temperature, and converted through a stilbene-type electrocyclization into a thermally stable orange species, which can be switched back using visible light. The behavior of these photoswitches was elucidated using NMR, which allowed to identify the photoisomers and some side-products, formed after prolonged UV irradiation.

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“…Generally speaking, photocyclization of stilbene analogues always require the presence of oxidant (O 2 or I 2 , KI, CuCl 2 , TCNE et al) for the reaction to proceed smoothly. [12][13][14] Luckily, we were able to obtain the cyclization products of 2,3-di(hetero)aryl-4H-chromen-4-ones without the requirement of any oxidant or additives. 15 However, the annulation product for less reactive 2,3-diphenyl-4H-chromen-4-one substrate was not obtained.…”

Section: Introductionmentioning

confidence: 98%