Diketene-based neat four-component synthesis of the dihydropyrimidinones and dihydropyridine backbones using silica sulfuric acid (SSA) Sadegh Rostamnia * , Kamran Lamei Organic and Nano Group (ONG), Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box 55181-83111,Maragheh, Iran Received 9 April 2012 Available online 4 July 2012 Abstract Heterocyclic skeleton building blocks to afford dihydropyrimidinones and dihydropyridines based on neat adducts of diketene, alcohols and aldehydes via silica sulfuric acid (SSA) catalyzed ring opening of diketene in four-component Biginelli-type and Hantzsch-type reactions are presented. # 2012 Sadegh Rostamnia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Diketene; Dihydropyrimidinone; Dihydropyridine; Heterocyclic skeleton; Silica sulfuric acid 1. Introduction Dihydropyrimidinones (DHPMs) and dihydropyridines (DHPs) are found to exhibit a wide spectrum of biological activities [1,2]. However a number of the reported protocols to synthesize DHPMs [3] and DHPs [4] in high yields requiring solvents and catalysts such as heavy metals are not acceptable in the context of costs or green catalyst. The developments in this area demand further searches for neat methods and diversity in reagents that could be superior to the existing ones with regard to generality, simplicity, high yields and handling. In other hand, after introduction of the silica sulfuric acid (SSA) as a useful heterogeneous solid acid by Zolfigol in 2001, many research papers have been published on its application in organic synthetic methodology and multicomponent reactions [5]. In this respect, we are interested in presenting potential neat diketene, alcohols and aldehydes adduct for preparation of the DHPMs and DHPs heterocyclic skeleton to overcome these limitations in presence of silica sulfuric acids (SSAs). In this new heterogeneous neat method which is based on using diketene as original, in situ source of variable b-ketoesters in four-component synthesis of DHPMs and DHPs is described. The neat approach, easiness and variability in derivatives of the present four-component procedure make it an interesting alternative to three-component approaches. www.elsevier.com/locate/cclet Available online at www.sciencedirect.com Chinese Chemical Letters 23 (2012) 930–932 * Corresponding author. E-mail addresses: rostamnia@maragheh.ac.ir, srostamnia@gmail.com (S. Rostamnia). 1001-8417/$ – see front matter # 2012 Sadegh Rostamnia. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. http://dx.doi.org/10.1016/j.cclet.2012.06.008