The condensation of 3-methyl-1-phenyl-5-pyrrolidinopyrazole-4-carboxaldehyde with N,N-dimethylbarbituric acid or Meldrum's acid followed by cyclization of the Knovenagel product by in a 'tert-amino effect' reaction resulted in the heterocyclic spiro-derivatives of pyrazolo3,4-eindolizine.
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