Heteropolyacid ionic liquid heterogeneously catalyzed synthesis of isochromans via oxa-Pictet–Spengler cyclization in dimethyl carbonate

A recyclable and efficient heterogeneous, green catalyst based on the synthesis of Keggin-type polyoxometalate (H(3)PMo(12)O(40)) and vitamin B1 analogue 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazol-3-ium (HEMT), i.e., [HEMTH]H(2)[PMo(12)O(40)] was prepared. Oxa-Pictet–Spengler cyclization of arylethanols and aldehydes were catalyzed to afford various substituted isochromans in moderate conditions with excellent yields using dimethyl carbonate (DMC) as a green solvent. Furthermore, this protocol was applicable in a gram-scale reaction, and the catalyst could be recycled eight times without significant loss of activity.