α,β-Unsaturated Aldehydes as C-Building Blocks in the Synthesis of Pyridines, 1,4-Dihydropyridines and 1,2-Dihydropyridines

N-heterocycles are ubiquitous structural units in a variety of biologically active compounds, pharmaceutical preparations, and natural complex molecules. Thousands of original scientific papers are published annually on various aspects of the formation of nitrogenous heterocycles and the study of their chemical and biological properties. Among them, the synthesis of pyridines and their dihydrogenated derivatives attracts the attention of chemists, which develop synthetic techniques, including those ones based on alpha,beta-unsaturated aldehydes. The minireview summarizes and highlights the recent advancements in the construction of pyridines, 1,2-dihydropyridines, and 1,4-dihydropyridines from transformations of 2-alkenals, covering the publications of the last five years.