Preyssler catalyst: An efficient catalyst for esterification of cinnamic acids with phenols and imidoalcohols

A series of eco-friendly Preyssler solid acids and their salts have been used as catalysts for the direct esterification of cinnamic acids with phenols or 2-(N-phthalimidoethanol). The catalysts were characterized by several techniques (DRS, FTIR, SEM, XRD, among others) and the effects of the reaction conditions were studied, including temperature, reaction time, and type and amount of catalyst. In the present work a series of eco-friendly Preyssler solid acids and their salts H 14[NaP 5W 29MoO 110] (PW), H 14[NaP 5W 30O 110] (PWMo), K 12.5Na 1.5[NaP 5W 30O 110]·15H 2O (PWK), K 12.5Na 1.5[NaP 5W 29MoO 110]·15H 2O (PWMoK) and 10% silica-supported H 14[NaP 5W 29MoO 110] (PWSiO 2), and H 14[NaP 5W 30O 110] (PWMoSiO 2) have been used as catalysts for the direct esterification of cinnamic acids with phenols or 2-(N-phthalimidoethanol). Effects of the reaction conditions were studied, including temperature, reaction time, and type and amount of catalyst. These solids were characterized by several techniques, such as diffuse reflectance spectroscopy, Fourier transformed infrared spectroscopy, optical and scanning electron microcopies, and X-ray diffraction, among others. The most adequate catalyst for performing the title reaction was H 14[NaP 5W 30O 110] (PWMo). The catalyst was applied for the synthesis of various substituted cinnamates, giving very good yields.