An efficient synthesis of a spirocyclic oxindole analogue

Article abstract of DOI:10.3390/11090700

An efficient, scaleable synthesis approach towards the spirocyclic oxindole analogue 1′-(tert-butoxycarbonyl)-2-oxospiro[indoline-3,4′- piperidine]-5-carboxylic acid (1) is described. The key steps are dianion alkylation and cyclization of ethyl 2-oxindoline-5-carboxylate (4) and demethylation of the resulting spirocyclic oxindole ethyl 1′-methyl-2- oxospiro[indoline-3,4′-piperidine]-5-carboxylate (5). The target compound was obtained in an overall yield of 35 % over eight steps without resorting to chromatographic purification.