Efficient and Ecofriendly Route for the Solvent-Free Synthesis of 4-Alkoxy-5H-chromen[2,3-d]pyrimidines Using Phosphonic Acid Functionalized KIT-6 Confined Ionic Liquid as Recoverable Catalyst

Abstract

Phosphonic acid functionalized KIT-6 confined ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF₄]) catalyzed the one-pot condensation reaction of iminochromenes and salicylaldehydes with different primary alcohols to achieve the corresponding 4-alkoxy-5H-chromen[2,3-d]pyrimidines under solvent-free conditions and in good yields. This efficient nanocatalyst can be recovered for at least five reaction runs without significant loss of either activity or confined IL.

GRAPHICAL ABSTRACT

Keywords:

• 4-Alkoxy-5H-chromen[2,3-d]pyrimidines
• KIT-6 confined ionic liquid
• one-pot synthesis
• phosphonic acid functionalized KIT-6

Notes

^a Yields refer to isolated pure products based on the reaction of 3(a–c) (1 mmol), salicylaldehydes 1(a–c) (1 mmol), alcohol 4(a–e) (1.5 mmol), cat. (2 mol %), at rt and solvent-free conditions. The reaction mixture was stirred for 40 min. All known products have been reported in the literature, and they were characterized by comparing their melting points and NMR spectra with authentic samples.^{[ 5 ]}

^a IL = [BMIm][BF₄].

^b The reactions run for 1 h.

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