Microwave-assisted Michael reactions of 3-(2′-nitrovinyl)indole with indoles on TLC-grade silica gel. A new, facile synthesis of 2,2-bis(3′-indolyl)nitroethanes

MK-10 clay catalyzed, one pot, three component and efficient synthesis of novel 4-(2′,5′-disubstituted-1′H-indol-3′-yl)-2,6-bis(2″,5″-disubstituted-1″H-indol-3″-yl)pyridine-3,5-dicarbonitrile under conventional and microwave irradiation

“…Microwaveassisted reactions, which required short reaction times are becoming more popular for organic chemists (12Á 14), due to eco-friendly nature, along with the fact that reactions can be run in open vessels (thus avoiding risk of high pressure) and synthesis can be performed on a preparative scale (15,16).…”

Functionalization of Indole and Pyrrole Cores via Michael-Type Additions

“…Although all indoles gave the expected unsymmetrical bis(indolyl)nitroethanes, 1-acetylindole (235) Scheme 51 did not provide the expected product. Interestingly, 1-alkylindoles 14 and 228-230 furnished both the expected products (52-63%) and the symmetrical bis(indolyl)nitroethanes as minor products (20-27%) (Scheme 52) [174,177]. The formation mechanism for the unexpected symmetrical product 237 is shown in Scheme 51.…”

“…Bis(indolyl)alkanes and their derivatives constitute an important part of bioactive metabolites both synthetic and natural terrestrial and marine origins [169][170][171][172][173][174]. Bioactive bis(indolyl)ethylamines 224-226 have recently been reported from marine sources, such as a tunicate and a sponge (Scheme 50) [169][170][171][172][173].…”

“…Recently, the use of 3-(2 -nitrovinyl)indole (227) as a Michael acceptor with indoles as nucleophile have been reported [174,177]. Michael reaction of 227 with eight 3-unsubstituted indoles (2, 14, 19, 228-235 silica gel, which acts as a mild acidic catalyst, under microwave irradiation or room temperature gave unsymmetrical bis(indolyl)nitroethanes (236a-h) in excellent yields (69-86%) (Scheme 51 and Table 6).…”

“…Furthermore, the symmetrical bis(indolyl)nitroethane 236a, as a model structure, could be reduced to the corresponding amine, isolated as its N-acetyl derivative 241 (Scheme 53) [174,177].…”