Oxidation of Cycloalkan [b] indoles with Iodine Pentoxide (I2O5)

• Published in: Chemical & pharmaceutical bulletin Vol. 35; no. 12; pp. 4700 - 4704
• Main Authors: YOSHIDA, KIYOSHI, GOTO, JIRO, BAN, YOSHIO
• Format: Journal Article
• Language: English
• Published: TOKYO The Pharmaceutical Society of Japan 1987; Pharmaceutical Soc Japan; Maruzen; Japan Science and Technology Agency
• Subjects: 1-hydroxytetrahydrocarbazole; 2-acylindole; 6-oxocycloalkan [b] -indole; Chemistry; Chemistry, Medicinal; Chemistry, Multidisciplinary; cycloalkan [b] indole; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with only one n hetero atom and condensed derivatives; indole oxidation; iodine pentoxide; Life Sciences & Biomedicine; Organic chemistry; Pharmacology & Pharmacy; Physical Sciences; Preparations and properties; Science & Technology; spiro oxindole; Structure effect; Regioselectivity; Nitrogen heterocycle; Bicyclic compound; Oxidation; Aqueous solution; Tricyclic compound; Ketone
• ISSN: 0009-2363; 1347-5223
• DOI: 10.1248/cpb.35.4700

Oxidation of cycloalkan [b] indoles (3) with iodine pentoxide (I2O5) in 80% aqueous tetrahydrofuran (THF) at room temperature regioselectively afforded 6-oxocycloalkan [b] indoles (4) in various yields. The yield of this oxidation depends on the size of the ring fused with the indole nucleus. The essential reaction species is I2O5, not HIO3, which might be generated by hydrolysis of I2O5 in the aqueous reaction medium. Oxidation of 1-hydroxytetrahydrocarbazole (5) under the above conditions afforded spiro oxindoles 6 and 7 in 36 and 39% yields, respectively, accompanied with only a trace of 1-oxotetrahydrocarbazole (4a).