Polycondensed heterocycles. Part 12: An approach to the synthesis of 2-acetyl-1′-methyl-1,2,3,4-tetrahydrospiro[isoquinoline-1,4′-pyrrolidine]-2′-one

The synthesis of ethyl (2-acetyl-1-cyano-1,2,3,4-tetrahydro-1-isoquinolyl)acetate was accomplished by cyanation/acylation of the dihydroquinoline ring system. The selective cobalt boride catalyzed reduction of the cyano group of the cyanoester intermediate was the key step to obtain the corresponding ethyl (1-aminomethyl-2-acetyl-1,2,3,4-tetrahydro-1-isoquinolyl)acetate which was cyclized by exposure to trimethylaluminum catalysis, leading to the novel spiro-polycondensed heterocyclic system.