Ethyl acetoacetate and a range of aldehydes in the presence of ammonium acetate are converted into 1,4-dihydropyridines under mild and solvent-free conditions with good to excellent yields.Key words: ethyl acetoacetate, 1,4-dihydropyridines, solvent-free conditions 4-Substituted Hantzsch 1,4-dihydropyridines 4 are analogues of NADH coenzymes and an important class of drugs. 1 Current literature reveals that 1,4-dihydropyridines exhibit neuroprotectant and platet anti-aggregratory activity, in addition to acting as cerebral antiischemic agents in the treatment of Alzheimer's disease and as chemosensitizers in tumor therapy. 2-5 Dihydropyridines are usually subsequently oxidized to pyridines. 6 The classical method for the synthesis of 1,4-dihydropyridines is a one-pot condensation of an aldehyde with ethyl acetoacetate, and ammonia either in acetic acid or refluxing in alcohol. 8 However, the yields of 1,4-dihydropyridines obtained by this method are generally low. Therefore, the development of an efficient and versatile method for the preparation of 1,4-dihydropyridines provides scope for further improvement towards milder reaction conditions and improved yields. Herein we wish to report a novel and efficient procedure for the synthesis of 1,4-dihydropyridines under mild and solvent-free condition.A range of 1,4-dihydropyridines 4 was synthesized from a combination of ethyl acetoacetate (1), aldehyde 2 and ammonium acetate 3 under mild and solvent-free conditions (Scheme 1 and Table 1). The reaction was completed 0.25-4.5 hours at 80°C and the crude product was isolated by precipitation upon addition of cooled water to the reaction mixture followed with vigorous shaking and decanting the aqueous layer. The residue was dissolved in a suitable solvent and anhydrous Na 2 SO 4 was added to the resulting mixture. The solvent was removed after filtration and 1,4-dihydropyridines obtained with high yield. 7In conclusion, the cheapness and the availability of the substrates, efficient work-up, and high yield make this method an attractive methodology. We believe that the present methodology addresses the current devise toward green chemistry due to high yields and atomic economy, fewer reagents.

O x i d a t i o n o f U r a z o l e s w i t h 1 , 3 -D i h a l o -5 , 5 -d i m e t h y l h y d a n t o i n

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A novel magnetically recoverable nanocatalyst with an amino vanadium oxo phthalocyanine pending, was synthesized, characterized and applied for the preparation of 3,4-dihydropyrano[c]chromenes derivatives.