DABCO-Amberlyst®15: A versatile heterogeneous catalyst in the multicomponent synthesis of tetrahydronaphthalenes and tetrahydroquinolines

Abstract

Bicyclic ortho-amino carbonitriles (tetrahydronaphthalenes) are crucial in their role to develop other heterocyclic compounds such as dicyanoanilines which can be used in optical electronic (optronic) devices. Tetrahydronaphthalenes can be obtained via the four-component reaction of malononitrile (2 equivalents), a cyclic ketone and an aldehyde. On the other hand, 5,6-substituted-2-amino-3-cyanopyridines (tetrahydroquinolines) have been found to be potent anti-cancer, anti-hypertensive, anti-microbial and anti-inflammatory agents. The synthesis of such compounds is directly linked by the single reactant replacement (SRR) technique because they derive from the combination of malononitrile, a cyclic ketone, an aldehyde and ammonium acetate as a nitrogen source. In this study, the activity of the heterogeneous metal-free catalyst DABCO supported on Amberlyst® 15 was explored in relation to the synthesis of both mentioned scaffolds. To the best of our knowledge, there are no instances in the literature where this has been achieved using the same catalyst, furthermore a novel successful DABCO-Amberlyst®15 catalysed one-pot sequential combination of multicomponent reactions (MCR²) was also reported.