1318 AMULRAO U. BORSE
increasing amount of Eaton’s reagent did not affect the yield and reaction time. Therefore it
was found that the 1.0 mmol of reagent was sufficient to push the reaction into completion
with high to excellent yield (Table 2).
To explore the scope of this reaction, we extended the procedure for the synthesis of variety
of Bis(indolyl)methanes using various aromatic aldehydes possessing either electron-
releasing or electron-withdrawing substituent’s in the ortho, meta and para positions (results
summarized in Table 3). It is observed that the reaction proceeds very efficiently with all the
aldehydes, substituents on the aromatic ring effect the conversion rate, aldehydes having
electron-withdrawing groups on the aromatic ring (Table 3,Entries 2-6, 8-10) react faster
than electron-donating groups (Table 3, Entries 7, 11, 13-17). Important features of this
procedure are that it is carried out under mild conditions; works well with all aldehydes
having functional groups (methyl, methoxy, nitro and halides) and provides the final
products in high yields.
Conclusion
In summary, the present methodology offers very attractive features such as shorter reaction
times, simple operations with extremely milder conditions, green aspects avoiding
hazardous organic solvents, toxic catalyst and waste, good to excellent yields with the help
of an inexpensive and commercially available Eaton’s reagent as a powerful substance for
the synthesis of Bis(indolyl)methanes at ambient temperature.
Acknowledgments
This work is supported by the University Grant Commission (UGC), New Delhi for
providing grant to the School of Chemical Sciences, North Maharashtra University (Jalgaon)
under SAP program. One of the authors (MNP) acknowledges UGC, New Delhi for SAP
fellowship under the scheme ‘Research Fellowship in Sciences for Meritorious Students’.
Authors are also thankful to Prof. R. S. Mali for his valuable guidance.
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Borse, Amulrao U.
