Influência da adição de CuCl2 e SnCl2 na relação metátese de olefinas vs isomerização do metil-eugenol usando complexo de Ru do tipo Grubbs segunda geração como catalisador

Abstract

SnCl2 or CuCl2 was used as an additive in the olefin metathesis of ME (metyl-eugenol) catalyzed by G2 [dicloro(2,5dimesitilimidazolildinilideno)(tricicloexil-fosfina)benzilidenorutênio(II)] at different reaction times, temperatures, and G2:chloride ratio, with a large G2:ME ratio of 1:1000 mol. The experiments occurred for 24 h at 25 or 50ºC with G2:chloride of 1:1 or 1:2 mol, and for 24 h at 25ºC with G2:chloride at 1:3 or 1:4 mol. In all cases, iso-ME and dimers from olefin metathesis were, in particular, accompanied in order to understand the chlorides effect. When adding chlorides at 25ºC for 24 h, the percentage of the products from olefin metathesis were increased substantially in relationship to the results without additive, reached c.a. 43% in the experiments with a G2:Sn of 1:1, in addition to the decrease of the iso-ME, which appears with a c.a. 20% in the mixture. For the ratio of 1:2 a tendency to form more dimers was observed in addition to the iso-ME decrease. When CuCl2 was added in ratios of Ru:Cu of 1:1 or 1:2 for 24 h at 25ºC, the quantity of the metathesis products was similar to the experiments in the absence of chloride, namely, less iso-ME was formed. At 50ºC, the chlorides’ presence favored the iso-ME formation for all cases when comparing with experiments at 25ºC; yet, when comparing the results without the additive, the iso-ME:ME ratio decreased, corroborating that a lower amount of isomer was obtained. With SnCl2, in both G2:Sn ratios, more olefin metathesis products were noted, which was also observed in the experiments at 25ºC in comparison to the analysis without chlorides. In the ratio 1:3 and 1:4 mol, only for SnCl2 as an additive, iso-ME formation was suppressed in the experiments for 24 h at 25ºC, and the sum of all the dimers from the ME olefin metathesis reached c.a. 80% (1:3) and c.a. 72% (1:4). The results, in particular for the suppression of the iso-ME, are discussed as a function of the system variables and the G2 degradation.