Indole frameworks have been extensively known as vital moieties in biological, agrochemical and pharmacological compounds.¹ Several MCR methods have been reported for the synthesis of substituted indoles. Within indole derivatives, 3-substituted indoles are versatile intermediates for the synthesis of a widespread range of indole compounds. The conjugate addition of indoles to Michael acceptors affords easy access to 3-substituted indole derivatives. ²

In continuing to our ongoing efforts towards developing efficient catalysts for different MCRs^3,4, we report herein a general route to 3-substituted indole derivatives via the three-component reaction of indoles, malononitrile and aldehydes promoted by a new alkaline functionalized chitosan, as a highly efficient and recoverable catalyst (Scheme 1).

­ Scheme 1. The three-component reaction of aldehydes, indole and malononitrile.

References

(1) Shiri, M. Chemical reviews 2012, 112, 3508.

(2) Qu, Y.; Ke, F.; Zhou, L.; Li, Z.; Xiang, H.; Wu, D.; Zhou, X. Chemical Communications 2011, 47, 3912.

(3) Dekamin, M. G.; Azimoshan, M.; Ramezani, L. Green Chemistry 2013, 15, 811.

(4) Dekamin, M. G.; Kazemi, E.; Karimi, Z.; Mohammadalipoor, M.; Naimi-Jamal, M. R. International journal of biological macromolecules 2016, 93, 767.