This thesis, Synthesis of heterocycles from α,β-unsaturated carbonyl compounds and bifunctional nucleophiles, comprises three chapters and ends with a list of references. The first chapter covers the literature up to date of the synthesis of 1,3-disubstituted propen-1-one by different techniques and their different mechanisms. Also this chapter includes the preparation of some heterocyclic compounds such as pyrimidine, isoxazole and pyrazole derivatives from chalcones. The second chapter deals with the discussion and interpretation of the results obtained starting chalcones 2.1a-d-2.3, from the above mentioned reactions. It discusses the assignment of the formed products by elemental analysis and spectral measurements such as IR, UV and NMR tools. It provides plausible mechanisms for the formation of the pyrimidine2.4a-d-2.6, isoxazole2.7a-d-2.10 and pyrazole2.11a-d-2.15 derivatives products. The third chapter discusses the methods for preparation of compounds 1-(4- pyridinyl)3-(4-substutitedphenyl) propen-1-one 2.1a-d, 1-(4-pyridinyl)3-(2-pyridinyl) propen- 1-one 2.2, 1-phenyl-3-(2-pyridinyl) propen-1-one 2.3. The chalcones 2.1a-d and 2.2 obtained from the reactions of 4-acetyl pyridine with 4-substituted benzaldehyde and 2-pyridine carboxylaldehyde while the compound 2.3obtained from acetophenone with2-pyridine carboxylaldehyde. Also the chapter includes the reaction of the previous chalcones with thiourea, hydroxylamine, hydrazine and 2-hydrazinopyridine to give pyrimidine2.4a-d-2.6, isoxazole2.7a-d-2.9and pyrazol 2.10a-d-2.15derivatives.These reactions have been accomplished by conventional thermal and ultrasonic methods. All the synthesized compounds were identified and characterized by elemental analysis, UV, IR and NMR spectra.