Modern Friedel-Crafts chemistry. Part 36. Facile synthesis of some new pyrido[3,2,1-jk]carbazoles via Friedel-Crafts cyclialkylations

Abstract

An efficient methodology for the synthesis of novel substituted pyrido[ 3,2,1-jk]carbazoles via Friedel-Crafts cyclialkylations is reported. The methodology was realized by a three-step protocol involving the addition of carbazole to 3-methylcrotononitrile. The resulting nitrile was subjected to alcoholysis to the desired ester, followed by addition of Grignard reagents to afford tertiary alcohols and/or reacted directly with different Grignard reagents to form the desired ketones. The latter ketones were converted to both secondary and tertiary alcohols by reduction with lithium aluminum hydride (LAH) and addition of Grignard reagents, respectively. These alcohols were cyclialkylated under Friedel-Crafts conditions catalyzed by AlCl 3/CH3NO2, p-toluenesulfonic acid (PTSA) or polyphosphoric acid (PPA) to give tri- and tetrasubstituted pyrido[3,2,1-jk] carbazoles. 2013 Copyright (CC) SCS.