Synthesis of spiro[tetralin-2,2'-pyrrolidine] and spiro[indan-2,2'-pyrrolidine] derivatives as potential analgesics

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Abstract
Spiro[tetralin-2,2''-pyrrolidine] (13) and spiro[6-methoxytetralin-2,2''-pyrrolidine] (17) were prepared by initial Michael condensation of 2-nitrotetralin and 6-methoxy-2-nitrotetralin, respectively, with methyl acrylate to give 7 and 8, both of which could be reductively cyclized to 10 and 11, followed by LiAlH4 reduction. Spiro[indan-2,2''-pyrrolidine] (15) was prepared in an analogous manner from 2-nitroindan, and spiro[6-hydroxytetralin-2,2''-pyrrolidine] (19) was prepared by O-demethylation of 17. Compound 13 and its N-methyl derivative 14, both showed good analgesic activity. Compounds 13-16 all possessed weak antidepressant properties, but neither 19 nor its N-methyl derivative had any significant CNS activity in mice.