Photo-Promoted Construction of 3-Spiro-2-sulfonylimino-indoline Skeletons via Cascade Reaction

The cascade reaction of 3-diazo-2-sulfonyliminoindolines and N-methoxymethyl-N-[(trimethylsilyl)methyl]benzylamines generates 2-sulfonylimino-1′,3′,4′,6′-tetrahydro-2'H-spiro[indoline-3,5′-pyrimidine] and spiro[indoline-3,3′-pyrrolidine] derivatives simultaneously under the catalysis of TFA and blue light irradiation. Their formation mechanisms were proposed on the basis of isotope-labeled experiments and HRMS analysis of the controlled experiment mixture, showing new reaction pathways. The current reaction provides a new strategy for the synthesis of biologically important spiro[indoline-3,3′-pyrrolidine]-2-one derivatives.