z Catalysis Green Nanospheres Natural Camphor Coated Ferrite as a Highly Efficient Nanocatalyst for the Synthesis of Dihydropyrimidine Derivatives Ali Maleki,* Pedram Zand, and Zahra Mohseni [a] Dihydropyrimidines are synthesized by a one-pot condensation of an aldehyde, b-ketoester and urea or thiourea in the presence of Fe 3 O 4 @camphor as a new heterogeneous magnetic nanocatalyst. The nanospheres morphology of the green natural camphor/ferrite was characterized by Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM) images, X-ray diffraction (XRD) pattern, energy-dispersive X-ray (EDX), vibrating sample magnetometer (VSM), N 2 adsorption-desorption by Brunauer–Emmett-Teller (BET) and inductively coupled plasma (ICP) analyses. The advantages of this new report are short reaction times, high yields, easy workup, low cost and eco-friendly protocol. The recoverable nanocatalyst was simply prepared and effectively employed for the one-pot multicomponent synthesis of dihydropyrimidine derivatives, for the first time, at room temperature. Introduction Multicomponent reactions (MCRs) are one of the most important green approaches for the preparation of highly functionalized organic compounds in modern synthetic chemistry. MCRs have all features that contribute to an ideal organic synthesis such as high atom efficiency, quick and simple implementation, time and energy saving, environment- friendly and they offer a target and diversity-oriented synthesis. MCRs in conjunction with heterogeneous catalysts offer great advantages due to atom economy, catalyst recyclability, low catalyst loading and high synthetic yields apart from the benefits that it may offer to the environmental aims. [1] Nanoparticles are key focus of research for a wide out- spread novel applications, not only because of their fabulous properties, but also due to nanosized compared with their bulk counterparts. Nanoparticles are intermediate between atomic and bulk level. At nano level, the properties greatly changed, as the size of the particles changed owing to their large surface to volume ratio. Owing to their wide spread applications, a lot of research has been carried out for the synthesis of one-dimen- sional nanostructures (nanotubes, nanorods, nanobelts, nanor- ings, nanohelics, nanowires, nanofibres, nanospheres, nano- flowers and nanosheets). Among nanomaterials, magnetic nanoparticles are of special interest to researchers owing to their praise worthy magnetic properties. Magnetic nanopar- ticles have a wide range of applications, including biotechnol- ogy, biomedicine, catalysis and environmental remediation. [2] Ferrite (Fe 3 O 4 ) has been used for a wide number of applications due to its superparamagnetic properties. Fe 3 O 4 nanoparticles have important role as a catalyst in MCRs. Due to high surface area to volume ratio, the interaction of OH groups on the surface of nano-Fe 3 O 4 with raw materials is increased. But, one important disadvantages in its properties is sensitivity to oxidation and agglomeration which has limited its usage. The solve this problem, the magnetic nanoparticles may be protected by various types of coating or supports. These shells not only protect the magnetic nanoparticles, but also provide a new platform for further functionalization that enhances the properties of the magnetic nanoparticles. Due to chemical and pharmaceutical importance of dihy- dropyrimidines (DHPMs), several reports are available for their synthesis. In most of the cases, homogenous catalysts such as clays, InCl 3 , 1-n-butyl-3-methyl imidazolium tetrafluoroborate, Bi(OTf) 3 and other reagents have been used for this trans- formation. [3] But, most of these methods suffer from one or more limitations, such as long reaction time, low yields, occurrence of several side reactions, drastic reaction conditions and tedious workup procedure. In connection with our previous works on design and development of recoverable nanocatalysts and MCRs, [4–9] herein, we wish to report a convenient and facile multicomponent one-pot synthesis of dihydropyrimidine derivatives 4a–l via the condensation of b-ketoesters 1, aldehydes 2 and urea or thiourea 3 in the presence of Fe 3 O 4 @camphor as a heteroge- neous magnetic nanocatalyst at room temperature in high yields with rather short reaction times (Scheme 1). To best of our knowledge, this is first report for the synthesis of dihydropyrimidine derivatives over Fe 3 O 4 @camphor via MCRs. [a] Dr. A. Maleki, P. Zand, Z. Mohseni Catalysts and Organic Synthesis Research Laboratory Department of Chemistry Iran University of Science and Technology Tehran 16846-13114, Iran Tel.: + 98 21 77240540 Fax: + 98 21 73021584 E-mail: maleki@iust.ac.ir Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/slct.201700131 Full Papers DOI: 10.1002/slct.201700131 2740 ChemistrySelect 2017, 2, 2740 – 2744  2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim