A irradiação de chalconas com microondas na ausência de solvente se mostrou um procedimento de "química verde" para a preparação, em bons rendimentos, de flavanonas. Diferentes catalisadores heterogêneos e catalisadores convencionais foram testados usando-se um forno de microondas doméstico. A irradiação de chalconas com 30% de ácido trifluoroacético, na presença de gel de sílica, levou a formação de onze flavanonas conhecidas e cinco novas, em bons rendimentos. Microwave irradiation of chalcones under solvent-free conditions resulted in a "green-chemistry" procedure for the preparation of flavanones in very good yields. Using an unmodified household microwave oven, different mineral supports and catalysts were tested. By irradiation of chalcones with 30% TFA over silica gel, eleven known flavanones and five new compounds were prepared in high yields.
There is still an international need to develop broad-spectrum sunscreen products with an adequate UVB/UVA balance, while the approved filters available in the UVA are scarce. Currently, one of the few UVA filters approved in the United States and Europe is tert-butylmethoxydibenzoylmethane (BMDM, avobenzone). However, this compound is unstable from aphotochemical point of view and cannot be used in combination with certain sunscreens. In this paper, we investigate the photochemical behavior of a set of dibenzoylmethanes and chalcones. In particular, we carry out their absorption and emission spectra, evaluate their photochemical degradation, and study their generation of free radicals and singlet oxygen photoproduction. Two compounds resultedin having the basic properties of UVA filters (2 -hydroxy-4-methoxychalcone and 2 -hydroxy-4-methoxydibenzoylmethane). Further studies are proposed, such as formulating the compounds into emulsions or other common cosmetic presentations, as well as combining them with broadly-used UVB filters. We have also considered the need to establish its toxicological profile.
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