Reactions of Pyrazolo [1, 5-α] pyrimidine Derivatives with Nucleophiles. IV. Some Reactions of 1, 4-Dihydrocyclopent [b] indoles

• Published in: Chemical & pharmaceutical bulletin Vol. 32; no. 11; pp. 4410 - 4418
• Main Authors: KURIHARA, TAKUSHI, NASU, KEIKO, HAGINAGA, SATOMI, MIHARA, KYOKO
• Format: Journal Article
• Language: English
• Published: Tokyo The Pharmaceutical Society of Japan 25.11.1984; Japan Science and Technology Agency
• Subjects: bicyclo [2.2.1]-hept [2, 3-b] indole
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.32.4410

4, 7-Dihydro-4-methyl-7-(N-methyl-3-indolyl) pyrazolo [1, 5-α] pyrimidine (3) obtained from pyrazolo [1, 5-α] pyrimidine (1) was treated with indole in the presence of an excess of triethyloxonium fluoroborate to give a mixture of 1, 4-dihydro-3-(3-indolyl) cyclopent [b] indoles (5, 6, 7 and 8). The reaction of 6 with potassium hydroxide in ethanol at room temperature gave the 1-hydroxy derivative (10), while under reflux 6 gave 1, 4-dihydro-1-oxocyclopent [b] indole (11). Treatment of 6 with formaldehyde gave the 1-hydroxymethyl derivative (13). m-Chloroperbenzoic acid oxidation of 6 afforded the 3, 4-dihydrocyclopent [b] indole (14). Furthermore, the reaction of 6 with activated olefins, such as maleic anhydride, maleimide, acrylonitrile and ethyl acrylate under reflux in benzene or acetonitrile gave [4+2] cycloadducts, bicyclo [2.2.1] hept [2, 3-b] indoles (17, 18, 20 and 21), via the 2, 4-dihydrocyclopent [b] indole intermediate (6').