Journal of the Korean Chemical Society 2013, Vol. 57, No. 2 Printed in the Republic of Korea http://dx.doi.org/10.5012/jkcs.2013.57.2.252 -252- DABCO-Catalyzed Green Synthesis of 2-Hydroxy-1,4-diones via Direct Aldol Reaction of Arylglyoxals in Water Mahnaz Saraei*, Bagher Eftekhari-Sis †, * , and Sakineh Mozaffarnia † Department of Chemistry, Payame Noor University, P. O. Box. 19395-3697, Tehran, Iran. * E-mail: m_saraii@yahoo.com † Department of Chemistry, University of Maragheh, P. O. Box. 55181-83111, Maragheh, Iran. * E-mail: eftekharisis@maragheh.ac.ir (Received November 27, 2012; Accepted March 13, 2013) ABSTRACT. A green and simple method to synthesize of 1,4-diketones via aldol reaction of arylglyoxals and ketones such as 1-(4-methoxyphenyl)-2-propanone, deoxybenzoin and substituted acetophenones in the presence of a catalytic amount of DABCO in water at room temperature has been reported. Corresponding 2-hydroxy-1,4-diones were obtained in moderate to high yields with simple separation of obtained solid from reaction mixture and recrystallization. Key words: 1,4-Diketones, Aldol reaction, Arylglyoxals, DABCO, Green chemistry INTRODUCTION Because of water is one of the most abundant and cheap solvents, and also makes the reactions environmentally amenable, much safer and easier to handle, 1 the organic reactions in aqueous media have attracted much attention in synthetic organic chemistry. 2 Also, reactions in water exhibit interesting reactivity and selectivity, which are dif- ferent from conventional organic solvents. The routes for formation of C−C bonds are the most important topics in synthetic organic chemistry. The aldol reaction is one of the most powerful C−C bond-forming reactions in organic synthesis, 3 leading to the β-hydrox- ycarbonyl structural units, which are found in several bio- logically active compounds, such as macrolide antibiotics and anti-cancer drugs, 4 and also are important building blocks in the synthesis of polyfunctional compounds and natural products. 3d,5 Additionally, 1,4-dicarbonyl compounds are versatile precursors for the synthesis of substituted cyclopenten- ones, 6 such as jasmones, 6g-i cuparenones, 6c and prostag- landins, 6j-l and also various heterocyclic compounds, for example, furan, thiophene, pyrrole, and pyridazine deriv- atives. 7 Thus the development of the synthetic methods of the 1,4-diketones have a significant impact on organic chemistry. A number of methods have already been reported for the preparation of 1,4-diketone derivatives, 8 and among them, most widely used approach is the Michael addition to α, β-unsaturated ketones of either unmasked acyl anions such as acyllithium, 9 and acyl-transition metal complexes, 10 or masked acyl anions and their equivalents. 11 Also, the preparation of 1,4-dicarbonyl compounds were carried out by the classic utilization of α-halo ketones, 12 by appli- cation of the Stetter reagent, 13 thiazolium salts in the pres- ence of a tertiary amine, 14 or 1,3-dithiane derivatives. 15 Recently, we have reviewed the application of arylgly- oxals (aromatic α-ketoaldehyds) in synthesis of hetero- cyclic compounds, 16 that encouraged us to work on aldol reaction of arylglyoxals to prepare 1,4-dicarbonyl com- pounds. However, aldol reaction with some α-dicarbonyl com- pounds such as benzil, isatin and ethyl phenylglyoxalate 17 to synthesize of 1,4-dicarbonyl compounds were previ- ously reported, 18 as the best of our knowledge, there is one report on aldol reaction of arylglyoxals in the literature using expensive chiral ligand with limited scope of prod- ucts, in which trimethylsilyl enols of ketones were used in CH 2 Cl 2 . 19 Herein, we wish to report the direct aldol reaction of dif- ferent ketones such as 1-(4-methoxyphenyl)-2-propanone, deoxybenzoin and substituted acetophenones with arylg- lyoxals in water to produce 2-hydroxy-1,4-diketones in the presence of a catalytic amount of DABCO. RESULTS AND DISCUSSION We first studied the aldol reaction of 1-(4-methoxyphe- nyl)propan-2-one 1a with phenylglyoxal hydrate 2a, which were prepared by oxidation of acetophenone using SeO 2 , 20 in water in the presence of different tertiary amines such