Catalytic Asymmetric 1,3-Dipolar Cycloadditions of Alkynes with Isatin-Derived Azomethine Ylides: Enantioselective Synthesis of Spiro[indoline-3,2′-pyrrole] Derivatives

The first catalytic asymmetric 1,3-dipolar cycloadditions of alkynes with isatin-derived azomethine ylides have been established in the presence of chiral phosphoric acid, affording synthetically and pharmaceutically important spiro[indoline-3,2-pyrroles] with quaternary stereogenic centers in high yields and excellent enantioselectivities (up to 99% yield, >99% ee). This protocol not only represents the first enantioselective 1,3-dipolar cycloadditions of alkynes with ketone-derived azomethine ylides, but also provides the first example of an enantioselective construction of spiro-oxindole-based 2,5-dihydropyrrole scaffold.