N,N-disulfo-1,1,3,3-tetramethylguanidinium carboxylate ionic liquids as reusable homogeneous catalysts for multicomponent synthesis of tetrahydrobenzo[a]xanthene and tetrahydrobenzo[a]acridine derivatives

Three new -SO3H functionalized N,N-disulfo-tetramethylguanidinium carboxylate ionic liquids [DSTMG][CX3COO], (where X = H, Cl, F) were prepared as viscous liquids from the reaction of [DSTMG][Cl] with equimolar amount of three carboxylic acids (AcOH, CCl3COOH and CF3COOH) for the first time at 60 degrees C in 1 h. Their structures were confirmed from IR, NMR and elemental analyses data. The Hammett acidity and TGA analysis were also investigated. The two ionic liquids [DSTMG][CF3COO] and [DSTMG][CCl3COO] were employed as reusable homogeneous catalysts for the one-pot synthesis of tetrahydrobenzo[a]xanthenones and tetrahydrobenzo[a]acridinones under solvent-free thermal method. The preparation of tetrahydrobenzo[a]acridinones was observed first time using 2-naphthol as reactant via four-component route in the presence of IL catalyst. (C) 2016 Elsevier B.V. All rights reserved.