The synthesis of 2-and 3-aryl indoles and 1,3,4,5-tetrahydropyrano[4,3-b]indoles and their antibacterial and antifungal activity

A series of 2- and 3-aryl substituted indoles and two 1,3,4,5-tetrahydropyrano[4,3-b] indoles were synthesized from indole and 5-methoxyindole. The 2- aryl indoles were synthesized from the 1-(phenylsulfonyl) indole derivatives using magnesiation followed by iodination. The 2-iodinated compounds were then subjected to Suzuki-Miyaura reactions. In addition, the 3-aryl indoles were made from the corresponding 3-bromoindoles using Suzuki-Miyaura reactions. The 1,3,4,5-tetrahydropyrano[4,3-b] indoles were also synthesized from 1-( phenylsulfonyl) indole by magnesiation followed by treatment with allylbromide. The product was then converted into [2-allyl-1-(phenylsulfonyl)-1H-indol-3-yl]methanol which upon exposure to Hg(OAc)(2) and NaBH4 afforded tetrahydropyrano[4,3-b] indoles. A number of the 2- and 3-aryl indoles displayed noteworthy antimicrobial activity, with compound 13a displaying the most significant activity (3.9 mu g/mL) against the Gram-positive micro-organism Bacillus cereus. (C) 2009 Elsevier Ltd. All rights reserved.