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Names | |
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Preferred IUPAC name 7,7-Dimethyl-2-(pyridin-4-yl)-5,7-dihydroimidazo[4,5-f]indol-6(1H)-one | |
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Properties | |
C16H14N4O | |
Molar mass | 278.315 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Adibendan is an inhibitor of phosphodiesterase 3. It has been tested in dogs for its effects on heart output and dilation of blood vessels. [1]
Synthesis: [2] Patent (Ex 14): [3]
N-benzyloxindole [7135-32-2] (1) is the starting material. Base facilitated alkylation with 2 molar equivalents of methyl halide (via the enolate stabilized carbanion) gives 1-benzyl-3,3-dimethylindol-2-one, PC11086219. Dissolving metal reduction (sodamide generated in situ) was the reaction medium which was employed to cleave the benzyl protecting group to give 3,3-dimethyloxindole [19155-24-9] (2). Nitration of this can obviously be achieved by the nitronium ion (generated in situ from nitric and sulfuric acids) to give 3,3-dimethyl-5-nitro-oxindole [100511-00-0]. Catalytic hydrogenation over palladium then reduces the nitro group to give 3,3-dimethyl-5-amino-oxindole [31523-05-4] (3). Treatment with acetic anhydride protects amino groups as the acetamide. Treatment with nitric acid is then able to add a nitro group on to the aromatic ring which is probably sterically directed. Treatment with acid hydrolyses the acetamide protecting groups to give 3,3-dimethyl-5-amino-6-nitro-oxindole, PC22162178 (4). Catalytic hydrogenation over platinum oxide reduces the nitro group to give 3,3-dimethyl-5,6-diamino-oxindole [100568-79-4]. The last step of the reaction sequence is a condensation with Isonicotinaldehyde [872-85-5], thus completing the synthesis of adibendan (5), respectively.