Construction of a spiro[pyrazolone-4,2′-pyridoindole] scaffold via a [3 + 3] cycloaddition of 2-indolylmethanol with a 4-aminopyrazolone-derived azomethine ylide

A one-pot [3 + 3] cycloaddition of 2-indolylmethanol with an in situ generated azomethine ylide derived from 4-aminopyrazolone is developed to access the spiro[pyrazolone–pyridoindole] scaffold.