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 (H3PMo12O40) and vitamin B1 analogue 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazol-3-ium (HEMT), i.e., [HEMTH]H-2[PMo12O40] 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.

Automated summary

A recyclable and efficient heterogeneous green catalyst based on the synthesis of Keggin-type polyoxometalate and vitamin B1 analogue was prepared, which catalyzed Oxa-Pictet-Spengler cyclization of arylethanols and aldehydes to afford various substituted isochromans in moderate conditions with excellent yields. The catalyst could be recycled eight times without significant loss of activity, demonstrating its potential for industrial applications.