A Tandem Approach to Functionalized Carbazoles from Indoles via Two Successive Regioselective Oxidative Heck Reactions Followed by Thermal Electrocyclization
作者:Joydev K. Laha、Neetu Dayal
DOI:10.1021/acs.orglett.5b02265
日期:2015.10.2
A direct one-pot approach to the synthesis of carbazoles (mono-, di-, and trisubstituted) and α-carbolines from readily available indoles or 7-azaindoles and alkenes is described. Based on mechanistic studies, the tandem reaction follows the sequence: palladium-catalyzed regioselective C-3 alkenylation/palladium-catalyzed C-2 alkenylation/thermal electrocyclization.
We synthesized a series of novel 3-indolyl cyclopent[b]indoles by trifluoroacetic acid mediated cyclodimerizations. The reaction showed high stereoselectivity and moderate to good yields. The influencing factors for stereoselectivity were systematically analyzed and a stepwise reaction mechanism was proposed. The cell viability tests in two colon and two lung cancer cell lines indicated the 1-benzyl-2phenyl-group in 3-indolyl cyclopent[b]indoles was critical for the observed lower IC(50)s in these compounds. Western blot analysis demonstrated that the compound inhibited the expression and phosphorylation of EGFR through altered HSP90 expression. Further cell cycle and cell cycle check point protein analyses showed expected anti-cellular proliferation and cell cycle arresting properties associated with suppressed EGFR expression and phosphorylation. These data revealed a novel molecular mechanism explaining the observed cytotoxicities for these compounds. (C) 2014 Elsevier Masson SAS. All rights reserved.