Indian Journal of Chemistry Vol. 56B, June 2017, pp. 663-669 Cobalt(II) nitrate hexahydrate, as an efficient catalyst for the synthesis of highly substituted piperidines and 1,8-dioxodecahydroacridine derivatives Mehrnoush Kangani, Nourallah Hazeri* & Malek-Taher Maghsoodlou Department of Chemistry, The University of Sistan and Baluchestan, P.O.Box 98135-674, Zahedan, Iran E-mail: n_hazeri@yahoo.com Received 7 March 2016; accepted (revised) 8 February 2017 Heterocycles, are an important group of organic compounds that have important role in the drug industry. Among the widespread heterocyclic compounds, nitrogen heterocycles have a distinct position because of their wide natural abundance and broad biological as well as pharmaceutical significance. A convenient and practical methodology for the one-pot, five- component synthesis of highly substituted piperidines has been developed via the condensation between arylaldehydes, amines and β-ketoesters in the presence of a catalytic amount of cobalt (II) nitrate hexahydrate at room temperature. In addition 1,8-dioxodecahydroacridine derivatives have been synthesis via the reaction between arylaldehydes, amines/ammonium acetate and dimedone in the presence of cobalt (II) nitrate hexahydrate as an efficient catalyst at thermal condition. One of the chief advantages of this methodology is high yields, short reaction times and simple work-up. Keywords: Piperidines, 1,8-dioxodecahydroacridine, cobalt(II) nitrate hexahydrate Over the past decade, multicomponent reactions (MCRs) have emerged as one of the excellent strategies to meet the demands for organic synthesis such as biologically active carbohydrate derivatives. In this approach two or more easily accessible components are combined in the reaction vessel to produce the final product 1 . The advantages of these reactions over conventional linear synthesis includes reduction of reaction time period, cost and energy, easily available starting materials, variable and high bond forming efficiency, resource effective, atom economical, eco-friendliness, operational simplicity, etc. Therefore, it has now a days become an important path for generating highly functionalized molecules with complexity and diversity by utilizing simply a straight forward single pot reaction without facing any problem in isolation and characterization of reaction intermediate 2 . Six-membered nitrogen heterocyclic compounds such as piperidine ring are very important because of their pharmacological and biological properties. The piperidines and their analogues exhibit diverse biological activities such as antihypertensive 3 , antibacterial 4 , anticonvulsant, and anti-inflammatory agents 5 , farnesyl transferase inhibitors 6 , norepinephrine re-uptake inhibitor (CTDP 31,446) (Ref 7), anti-HIV properties 8 and antidepressant drugs 9 . Furthermore, substituted piperidines have been identified as an important class of therapeutic agents in the treatment of Parkinson’s disease 10–12 , prolactinoma 13 , schizophrenia 14–16 , influenza infection 17,18 , cancer metastasis 19–21 , viral infections including AIDS 22,23 , obesity, and diabetes 24–26 . These extensive investigations have resulted in the development of various synthetic methods for the synthesis of substituted piperidines 27-34 . In view of the immense biological and pharmaceutical significance of these heterocycles, the introduction of an efficient method for the preparation of these compounds is still in demand. As a part of our continuing interest in the development of multi- component reactions for the synthesis of functionalized piperidine 35–38 , we report here an efficient and convenient procedure for the synthesis of highly substituted piperidines using cobalt(II) nitrate hexahydrate as an efficient catalyst in EtOH at ambient condition (Scheme I). In addition, 1,8-dioxodecahydroacridine was synthesis using the mentioned catalyst (Scheme II). Experimental Section Melting points of all compounds were measured on an Electrothermal 9100 apparatus and are uncorrected. The 1 H and 13 C NMR spectra were obtained on Bruker DRX-400 instrument at 300 MHz and 75 MHz respectively, using CDCl 3 as solvent. The mass spectra were recorded on a Shimadzu GCMS-QP5050A mass spectrometer operating at an