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 AlCl3/CH3NO2, p-toluenesulfonic
acid (PTSA) or polyphosphoric acid (PPA) to give tri- and tetrasubstituted
pyrido[3,2,1-jk]carbazoles.