Oxidative cleavage of isoeugenol to vanillin under molecular oxygen catalysed by cobalt porphyrin intercalated into lithium taeniolite clay

Abstract

Three types of Co–porphyrin complexes differing in their porphyrin-ring substituents and nonionic or cationic structure were intercalated into lithium taeniolite (LiTN) using a simple cation exchange method. All the intercalated catalysts displayed expanded clearance spaces (in the range of 0.30–0.51nm) compared with that of the parent LiTN (0.24nm). The catalysts were applied for the oxidative cleavage of isoeugenol to vanillin with molecular oxygen as the sole oxidant, and the reaction proceeded effectively under mild reaction conditions. The highest vanillin selectivity of 72% was obtained with CoTPyP/TN, which had the widest clearance space among the three Co–porphyrin catalysts. These intercalated catalysts showed high stability during oxidation, enabling their recycling for at least three runs.