528-33-6Relevant articles and documents
Photocatalytic Oxidative [2+2] Cycloelimination Reactions with Flavinium Salts: Mechanistic Study and Influence of the Catalyst Structure
Hartman, Tomá?,Reisnerová, Martina,Chudoba, Josef,Svobodová, Eva,Archipowa, Nataliya,Kutta, Roger Jan,Cibulka, Radek
, p. 373 - 386 (2021/02/01)
Flavinium salts are frequently used in organocatalysis but their application in photoredox catalysis has not been systematically investigated to date. We synthesized a series of 5-ethyl-1,3-dimethylalloxazinium salts with different substituents in the positions 7 and 8 and investigated their application in light-dependent oxidative cycloelimination of cyclobutanes. Detailed mechanistic investigations with a coumarin dimer as a model substrate reveal that the reaction preferentially occurs via the triplet-born radical pair after electron transfer from the substrate to the triplet state of an alloxazinium salt. The very photostable 7,8-dimethoxy derivative is a superior catalyst with a sufficiently high oxidation power (E=2.26 V) allowing the conversion of various cyclobutanes (with Eox up to 2.05 V) in high yields. Even compounds such as all-trans dimethyl 3,4-bis(4-methoxyphenyl)cyclobutane-1,2-dicarboxylate can be converted, whose opening requires a high activation energy due to a missing pre-activation caused by bulky adjacent substituents in cis-position.
Photodimerization of cinnamic acids controlled by molecular assemblies of surfactant amine N-oxides
Nakamura, Tomotaka,Takagi, Katsuhiko,Itoh, Mariko,Fujita, Kaori,Katsu, Hiroyuki,Imae, Toyoko,Sawaki, Yasuhiko
, p. 2751 - 2755 (2007/10/03)
UV irradiation of cinnamic acids 1 involving a complex with surfactant amine N-oxides (CnDAO, n = 12, 14 and 16) as vesicles in water leads to the formation of cyclodimers (i.e. β-, δ-truxinic and/or α-truxillic acids ?). Decreasing the molar ratios of 1 to CnDAO causes the vesicles to transform into rod-like micelles and the yield of the cyclodimers decreases. The addition of HCl or NaOH to aqueous solutions of 1 and CnDAO brings about sharp changes in the self-assembly structures from vesicles to micro emulsions or rod-like micelles, accompanied by a change in product distribution in the photolysis of the complex 1. Upon addition of photoinactive carboxylic acids, phenylpropionic and palmitic acids to the 1 and C16DAO system, the rod-like micelles change into vesicles by formation of a complex with C16DAO leading to the observation of a dilution effect in the photodimerization upon addition of phenylpropionic acid. However, no dilution effect is observed for the palmitic acid. This is found to be attributable to the difference in degrees of mixing of 1 with the acids in the vesicles. These results show that photodimerization of 1 incorporated in CnDAO is controlled by a variety of molecular assemblies, i.e. rod-like micelles and homogeneous or heterogeneous vesicles.
Photochemical cyclodimerization of cinnmamic acids included in surfactant amine oxides
Takagi,Nakamura,Katsu,Itoh,Sawaki,Imae
, p. 135 - 138 (2007/10/03)
Photocyclodimerization of unsubstituted and p-methoxy substituted cinnamic acids incorporated in micelles, vesicles or microemulsions formed by dodecyl-(C12DAO) and hexadecyl-dimethylamine oxides (C16DAO) has been studied in water. The dimerization proceeds in the vesicle much more efficiently than in the micelles with preferable formation of head-to-head dimers. The photoreactivity and the stereochemistry of cyclodimers are affected by structural change of the molecular aggregates.
