Background:
Much attention has been focused on heterogeneous catalysts. Reactions with
these recoverable and reusable catalysts are clean, selective with high efficiency. Among the heterogeneous
solid acid catalyst in organic synthesis, Carbon-Based Solid Acids (CBSAs), which are important
solid acid with many practical and research applications have been extensively studied. In this
work, green Pistachio peel, a biomass waste, was converted into a novel carbon-based solid acid catalyst
(Pis-SO3H).
Objective:
The aim of this work is to synthesize highly sulfonated carbon as an efficient, recyclable,
nontoxic solid acid catalyst by simultaneous sulfonation, dehydration and carbonization of green Pistachio
peel as biomass and investigate the catalytic activity of Pis-SO3H in acetalization, thioacetalization,
acylation of aldehydes and synthesis of 3,3'-Arylmethylene-bis(4-hydroxycoumarin) derivatives.
Method:
Pis-SO3H was synthesized by an integrated fast one-step hydrothermal carbonization and
sulfonation process in the presence of sulfuric acid. The characterization of the physicochemical properties
of Pis-SO3H was achieved by XRD, FT-IR, FE-SEM, and elemental analysis.
Results:
The result of acid-base titration showed that the total acidity of the catalyst was 7.75 mmol
H+g−1. This new heterogeneous catalyst has been efficiently used for the chemoselective thioacetalization,
acetalization and acylation of aldehyde and the synthesis of biscoumarins under solvent-free conditions.
All the reactions work easily in high yields. The antimicrobial activity of some of the biscoumarins
was evaluated in screening by disk diffusion assay for the zone of inhibition.
Conclusion:
The catalytic activity of the Pis-SO3H was investigated during acetalization, thioacetalization,
acylation and synthesis of biscoumarins. The results of protection of carbonyl groups and synthesis
of biscoumarins in the present work offer effective alternatives for environmentally friendly utilization
of abundant biomass waste.
Synthesis of Medicinally Important Indole Derivatives: A Review
