Green Method To Preparing Oxindole-Fused Spirotetrahydrofuran Scaffolds through Methanesulfonic Acid-Catalyzed Cyclization Reactions of 3‑Allyl-3-hydroxy-2-oxindole in Water

Water is an ideal solvent for chemical transformations in environmentally
friendly and sustainable processes. An operationally simple, metal-free,
and green approach to the synthesis of oxindole-fused spirotetrahydrofurans
from 3-allyl-3-hydroxy-2-oxindoles in water is described. This method
requires only cheap methanesulfonic acid as a catalyst and eliminates
the need of complicated reagents. This atom- and step-economical transformation
is highly efficient, which provides a new approach for the construction
of oxindole-fused spirotetrahydrofuran molecules with potential pharmaceutical
interest.