Additive-Free Three-Component Synthesis of Spiro-isoxazolidine-oxindoles Employing Trifluorodiazoethane

An
efficient three-component protocol for the synthesis of trifluoromethylated
spiro-isoxazolidine-oxindoles has been developed. This approach employs
the 1,3-dipolar cycloaddition of trifluoromethyl nitrone, generated
in situ from trifluorodiazoethane and nitrosoarene, with phenacylideneoxindoles.
A range of phenacyclideneoxindoles and nitrosoarenes can be subjected
to this reaction to generate the spiro-isoxazolidine-oxindole derivatives.
The reductive ring-opening reaction of isoxazolidines carried out
to demonstrate the synthetic potential of our strategy resulted in
an interesting rearrangement to yield pyrroloquinoline derivatives.