NaHSO4/SiO2: An effective catalyst for the eco-friendly synthesis of α, α'-bis (arylmethylidene) cycloalkanones under solvent-free conditions

摘要

α,α'-bis (substituted benzylidene) cycloalkanones are of interest since they are important precursors for the synthesis of bioactive pyrimidine derivatives [1] and perfumes [2]. These compounds have been prepared via a tandem cross-aldol condensation of cycloalkanones with aromatic aldehydes using Yb(OTf)3 [3], Polymer-supported sulphonic acid and aqueous micellar media as catalysts. However, there are one or more of the disadvantages such as the use of costly catalysts, use of hazardous reagents and often long reaction times for complete conversion. In addition, most of these reactions were accompanied by low chemoselectivity, also self-condensations were observed rather than cross-aldol condensations, which caused problems in their purification. It is therefore important to find a more convenient method for the preparation of these compounds. In recent years the use of solid supported reagents has received increased attention in organic synthesis due to their ease of handling, greater selectivity, simple work-up and recoverability as well as economic and environmental considerations. NaHSO4 supported on silica gel (NaHSO4/SiO2) has recently been used in various organic reactions as an inexpensive and nontoxic and reusable catalyst to give the corresponding products in high yield. This catalyst has been used efficiently for many organic reactions.