Biowaste-Derived Heterogeneous Catalyst for the One-Pot Multicomponent Synthesis of Diverse and Densely Functionalized 2-Amino-4W-Chromenes

摘要

Chromene skeletons are crucial structural motifs existing in abundant natural products and drug molecules.1 These oxygen-containing heterocyclic compounds have a broad range of biological properties such as antimicrobial,2 anti-HIV,3 anti-inflammatory, and cytotoxic activities.5 They are being investigated in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Notably, several drug molecules possessing 4H-chromene moieties are currently in use for the treatment of such ailments as asthma, hypertension, ischemia and urinary incontinence. The synthesis of these O-heterocycles involves the three-component coupling of C-H activated acids with malononitrile and aromatic aldehydes in the presence of homogeneous and heterogeneous catalysts such as piperidine,12 triethylamine,13 DBU,14 (NH4)2HPO4)15 POPINO,16 piperazine,17 aqueous K2CO3,18 hydrotalcite (HT),19 TiO2 nanowire,20 MgO,21 mesolite,22 nanozeolite clinoptilolite,23 trichloroisocyanuric acid24 and 2-aminopyridine.25 In no denial of fact, the reported methods are creditable;; however, the implication of hazardous reagents and solvents, lengthy processes, energy investment for heating purposes and complications in the separation of products are realistic problems associated with these methods. Considering the diverse functionality of 2-amino-4H-chromenes, it was deemed worthwhile to explore a convenient protocol for the synthesis of these heterocycles.