An environmentally friendly and efficient synthesis of a series of 1, 4-dihydropyridines was developed by the practical one-pot reactions of aldehydes with ammonium acetate and 1, 3- dicarbonyl compounds such as alkyl acetoacetate, 5, 5-dimethyl-1, 3-cyclohexanedione, 1, 3- cyclohexanedione, and 2, 4-pentanedione in water without any additives under refluxing conditions.
[Khanmohammadi, Mohammadreza; Dalali, Nasser; Karami, Farshad; Garmarudi, Amir Bagheri; Nemati, Hossein Bulletin of the Chemical Society of Ethiopia, 2012 , vol. 26, # 2 p. 299 - 304]