Triethylamine-bonded sulfonic acid ([Et₃N–SO₃H]Cl): a highly efficient and homogeneous catalyst for the condensation of 2-naphthol with arylaldehydes and amides (alkyl carbamates or thioamides)

Abstract

Ionic liquid triethylamine-bonded sulfonic acid ([Et 3N–SO 3H]Cl, N,N-diethyl-N-sulfoethanammonium chloride) is utilized as a highly efficient, inexpensive and homogeneous catalyst to promote the following one-pot multi-component organic transformations under solvent-free conditions: (i) the condensation of 2-naphthol with arylaldehydes and amides leading to 1-amidoalkyl-2-naphthols, (ii) the reaction of 2-naphthol with aromatic aldehydes and alkyl carbamates to produce 1-carbamatoalkyl-2-naphthols, and (iii) the condensation between 2-naphthol, arylaldehydes and thioamides leading to 1-thioamidoalkyl-2-naphthols. High yields, short reaction times, efficiency, generality, clean process, simple methodology, low cost, easy work-up, ease of preparation of the catalyst, and environmentally benign conditions are some advantages of the protocols.