Sustainable Sulfonic Acid Functionalized Tubular Shape Mesoporous Silica as a Heterogeneous Catalyst for Selective Unsymmetrical Friedel–Crafts Alkylation in One Pot

The development of
general and more sustainable heterogeneous catalytic
processes for Friedel–Crafts (FC) alkylation reactions is a
key objective of interest for the synthesis of pharmaceuticals and
commodity chemicals. Sustainable heterogeneous catalysis for the typical
FC alkylation of an easily accessible carbonyl electrophile and arenes
or with two different arene nucleophiles in one-pot is a prime challenge.
Herein, we present a resolution to these issues through the design
and utilization of a mesoporous silica catalyst that has been functionalized
with sulfonic acid. For the synthesis of sulfonic acid-functionalized
mesoporous silica (MSN-SO3H), thiol-functionalized mesoporous
silica was first synthesized by the co-condensation method, followed
by oxidation of the thiol functionality to the sulfonic acid group.
Sulfonation of mesoporous silica was confirmed by 13C CP
MAS NMR spectroscopy. Further, the devised heterogeneous catalysis
using MSN-SO3H has been successfully employed in the construction
of diverse polyalkanes including various bioactive molecules, viz
arundine, tatarinoid-C, and late-stage functionalization of natural
products like menthol and Eugenol. Further, we have utilized this
sustainable technique to facilitate the formation of unsymmetrical
C–S bonds in a one-pot fashion. In addition, the catalyst was
successfully recovered and recycled for eight cycles, demonstrating
the high sustainability and cost-effectiveness of this protocol for
both academic and industrial applications.