A new triazine-thiophene based porous organic polymer as efficient catalyst for the synthesis of chromenes via multicomponent coupling and catalyst support for facile synthesis of HMF from carbohydrates

Abstract

Functionalized porous organic polymers are very demanding and promising material in heterogeneous catalysis due to their convenience in synthesis and versatility in framework composition. Further, owing to the tunable porosity, high specific surface area, ease of functionalization and chemical stability, this class of porous polymers have huge potential to be employed both as catalysis and catalyst support. Herein, we report N-rich triazine-thiophene based microporous polymer TrzDBTH through the Friedel-Craft alkylation reaction of tripodal building block 2,4,6-tris[4-(bromomethyl)phenyl]-1,3,5-triazine with dibenzothiophene (DBTH) and used it as a heterogeneous base catalyst for one-pot synthesis of biologically important chromene derivatives. Further, sulfonation to this TrzDBTH material yielded sulfonated hyper-crosslinked porous polymer namely STrzDBTH, which can be used as solid acid catalyst for the synthesis of valuable chemical intermediate 5-hydroxymethylfurfural (HMF) from different biomass derived carbohydrates. As a base catalyst, TrzDBTH provides chromene yields from 88 to 93% and its sulfonated derivative STrzDBTH provides the HMF yields from 57 to 97% for different carbohydrate substrates. Both the materials displayed high recycling efficiencies for several catalytic cycles. Thus, these triazine-thiophene based porous organic polymers offer very economical, scalable and recyclable routes for the synthesis chromene derivatives and HMF.