Synthesis of new amidoalkyl naphthol derivatives using Fe3O4@SiO2piperazine sulfuric acid as catalyst under solvent free conditions

1-Amidoalkyl-2-naphtol derivatives are of significant importance since they have been frequently applied as hypotensive and bradycardiac agents [1]. 1-Amidoalkyl-2-naphtol can be converted to 1,3-oxazine derivatives [2]. 1,3-Oxazines have potentially different biological activities including antibiotic, antitumor, analgesic, anticonvulsant, antipsychotic, antimalarial, antianginal, antihypertensive, and antirheumatic properties. 1-Amidoalkyl-2-naphtol can be prepared by multi-component condensation of aryl aldehydes, 2-naphtols, and amide derivatives or acetonitrile in the presence of different Lewis or bronsted acids such as p-TSA, ZrOCl2, Yb(OTf)3/[Bmim]BF4, FeCl3.SiO2, I2, sulfamic acid [3]. However, many of the reported methods are associated with one or more of the following drawbacks: low product yield, expensive or air-sensitive reagents, long reaction time, harsh reaction conditions, the used of toxic, corrosive and non-reusable catalysts, and the use of large amounts of catalyst. Therefore, the development of more efficient procedures for the synthesis of 1-amidoalkyl-2-naphthols is still needed. A simple and eco-friendly method for the preparation of amidoalkylnaphthols derivatives via the three-component condensation reaction of aldehydes, 2-naphtol, and amids in the presence of acidic catalyst is described (Figure 1).