Synthesis of 1-alkyl triazolium triflate room temperature ionic liquids and their catalytic studies in multi-component Biginelli reaction

Abstract

Synthesis of three Brnsted acid-based ionic liquids, namely, 1-ethyl-1,2,4-triazolium triflate (1a), 1-propyl-1,2,4-triazolium triflate (1b) and 1-butyl-1,2,4-triazolium triflate (1c), is described. These ionic liquids have been employed as catalysts for convenient and high-yielding one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones and 3,4-dihydropyrimidin-2(1H)-thiones, which are Biginelli reaction products. Advantages of the methodology are operational convenience, short reaction times, avoidance of chromatographic purification and non-production of toxic waste. Further, the catalysts are easily recovered and reused without any noticeable diminution in their catalytic activity. Synthesis of room temperature Bronsted acid-based catalysts and their utility as catalysts for convenient and high-yielding one-pot synthesis of 3,4 dihydropyrimidin-2(1H)-ones, which are Biginelli reaction products, are described. The catalysts permit recyclability without any loss of catalytic activity.