Novel tetracyclic spiropiperidines. II. Synthesis of 2-aryl-2,3-dihydrospiro[benzofuran-3,4′-piperidines]

A series of 2-aryl-2,3-dihydropsirobenzofuran-3,4′-piperidines] has been synthesized as potential psychotropic agents via an efficient intramolecular fluorine displacement reaction. Treatment of a key intermediate, 4-cyano-4-(2-fluorophenyl)-1-methylpiperidine ( 2 ), with a large excess of phenylmagnesium bromide in refluxing tetrahydrofuran led to some 2-arylspiro3H-indole-3,4′-piperidine] derivatives, 10 and 11 , whose structures are elucidated on the basis of chemical and spectral evidence.