The catalytic Friedel-Crafts alkylation of indoles with nitroalkenes to furnish 2-indolyl-1-nitroalkane derivatives at room temperature with moderate to excellent yields is reported using nanocrystalline titanium(IV) oxide (nano-TiO2) catalyst. In all cases, a single regioisomer was obtained. After completion of the reaction, the catalyst was recovered by centrifugation and activated under a nitrogen flow for 1h at 250 degrees C for further reuse. The nano-TiO2 can be reused for four cycles with a slight decrease of activity under the same reaction conditions.
A combination of water and microwave irradiation promotes the catalyst-free addition of pyrroles and indoles to nitroalkenes
作者:Margherita De Rosa、Annunziata Soriente
DOI:10.1016/j.tet.2010.02.055
日期:2010.4
A combination of water and microwave irradiation was used for the first time to perform a catalyst-free nitro-Michael addition of pyrroles and indoles. Under superheated conditions, the water trends to ionize by changing its chemical and physical properties. Therefore, we performed a new green-protocol using the water either as environmentally no harm solvent or as catalyst. The reaction success is independent from the kind of pyrrole, indole or nitroalkenes rapidly affording the corresponding adducts and giving excellent yields. (C) 2010 Elsevier Ltd. All rights reserved.
Chauhan, Pankaj; Singh, Sarbjit; Chimni, Swapandeep Singh, Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 2013, vol. 52, # 2, p. 245 - 251