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

The cascade reaction of 3-diazo-2-sulfonyliminoindolines and <i>N</i>-methoxymethyl-<i>N</i>-[(trimethylsilyl)methyl]benzylamines generates 2-sulfonylimino-1',3',4',6'-tetrahydro-2'<i>H</i>-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.