Synthetic Approaches to Calycanthaceae Alkaloids. II. A Synthesis of 1, 1'-Dimethyl-3, 3'-bis (2-aminoethyl)-3, 3'-bioxindole.

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Alkylation of 1, 1'-dimethyl-3, 3'-bioxindole (V) was carried out. A higher-melting isomer (VIIa) was obtained by dimethylation of (V) with sodium hydride in benzene. while a lower-melting isomer (VIIb) was obtained by dimethylation of (V) with sodium amide in liquid ammonia. Cyanomethylation of (V) with sodium hydride in benzene afforded (VIIIa), which was further cyanomethylated by chloroacetonitrile with potassium carbonate, sodium iodide, and acetone to give (IX), which was also obtained by direct biscyanomethylation with the latter reagents. Two other 3, 3'-disubstituted 3, 3'-bioxindoles (X, XII) were also prepared by analogous alkylation. The compound (III), which was considered to be an attractive intermediate for the synthesis of (I) and (II), was obtained by catalytic reduction of (IX).