186
H. Alinezhad et al. / Chinese Chemical Letters 21 (2010) 183–186
Scheme 3. Chemoselectivity of aldehyde in reaction with indole in the presence of a ketone.
steric crowding in corresponding DIMS, aliphatic and aromatic ketones (Table 2, entries 25, 26 and 31) reacted with
longer reaction times and their yields of products was lower. The outstanding feature of this procedure is the synthesis
of diindolyl methanes of pyrrole, furan, thiophen and pyridine in good to excellent yields. By controlling the molar
ratio of indole, condensation of a dialdehyde i.e. terephthaldialdehyde to the corresponding DIMS (Table 2, entries 10
and 20) was achieved.
As shown in Table 2, entries 33 and 34, we have also prepared 3,30-diindolyloxindole derivatives by the reaction
between isatin and indoles using this procedure.
This method is also highly chemoselective for aldehydes. For example, when a 1:1 mixture of benzaldehyde and
cyclohexanone reacted with indole in the presence of CSA, only phenyl-3,30-bis-indolylmethane was obtained, while
cyclohexanone did not give the corresponding product under this reaction conditions (Scheme 3).
3. Conclusion
In conclusion, we have provided a powerful and convenient procedure for the preparation of bis-indolylmethanes
and 3,30-diindolyloxindole derivatives. Mild reaction condition, improvement of yields of the products, using friendly
process and easy work up procedure are the merits of this procedure.
Acknowledgment
Financial support of this work from the Research Council of Mazandaran University is gratefully acknowledged.
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