How is 2-Methyl-2-propanyl 5-chloro-1,2-dihydro-1'H-spiro[indole-3,4'-piperidine]-1'-carboxylate (CAS: 637362-21-1) typically synthesized?

2-Methyl-2-propanyl 5-chloro-1,2-dihydro-1'H-spiro[indole-3,4'-piperidine]-1'-carboxylate is typically synthesized via a multistep process involving coupling reactions and ring formation. Commonly, it involves the reaction of 5-chloro-1,2-dihydro-1'H-spiro[indole-3,4'-piperidine]-1'-carboxylic acid with 2-methyl-2-propanol in the presence of a coupling agent like HATU and a base such as DIPEA. The reaction proceeds with high selectivity and yields up to 90%.