Bartoli G1, Bosco M, Giuli S, Giuliani A, Lucarelli L, Marcantoni E, Sambri L, Torregiani E.
J Org Chem. 2005 Mar 4;70(5):1941-4.The combination of cerium(III) chloride heptahydrate and sodium iodide supported on silica gel is known to promote Michael-type additions. Continuing our work on solvent-free conditions, the CeCl3.7H2O-NaI-SiO2 system catalyzes the addition of a variety of indoles and nitroalkenes, giving 2-indolyl-1-nitroalkane derivatives in good yields. Development of this method has resulted in a new protocol for the synthesis of 4-substituted beta-carbolines.