Synthesis of Bis(indolyl)methanes using a Catalytic Amount of ZnO under Solvent‐Free Conditions

Yonemitsu-type condensations catalysed by proline and Eu(OTf)3

“…65,66 However, its formation is proved by the isolation of bis-indole derivative 19, which can only come from 18 by addition of a second molecule of indole. The formation of 3,3 0 -bis-indolylmethanes from indole and carbonyl compounds is catalysed by Lewis acids [67][68][69][70][71] as well as strong Brønsted acids. 65,66 Because L-proline is a weak Brønsted acid, its catalytic effect in the mechanism of Scheme 2 is expected to be negligible with respect to that of europium ion.…”

Bismuth triflate-catalyzed condensation of indoles with acetone

“…Finally, the structure of 8a was unambiguously conrmed by X-ray (Fig. Further variation of substituent on N-methylindole was studied, and it was found that N-methylindoles with electron donating groups gave corresponding N-methylindolyl-cyclopenta[b]indole derivatives, whereas N-methylindoles with electron withdrawing substituted gave bis(N-methylindolyl)propane (7) instead of N-methylindolyl-cyclopenta[b]indoles (8). The structure and spectral data of 8a were in agreement with the earlier reported product of the reaction between N-methylindole with acetone (Table 3).…”

p‐Dodecylbenzenesulfonic Acid: An Efficient Brønsted Acid‐Surfactant‐Combined Catalyst to Carry out Diverse Organic Transformations in Aqueous Medium

“…In the recent past a huge number of protocols were reported for the synthesis of bis (indolyl)methanes employing various homogeneous, heterogeneous metal catalysts, nano‐catalysts, ionic liquids etc . Use of toxic metal catalysts and organic solvents, long reaction times, harsh reactions conditions are some of the demerits of these reported protocols.…”