Synthesis of spirocyclic 4,5,5a,6,7,8-hexahydro-1H-pyrazolo[3,4-e]indolizine derivatives

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 Knövenagel product by in a ‘tert-amino effect’ reaction resulted in the heterocyclic spiroderivatives of pyrazolo[3,4-e]indolizine.