Selected Cycloaddition and Heterocyclization Reactions with Unusual Acetylenic and Allenic Starting Compounds

This chapter deals with selected reactions discovered in years, 2000–2012 initiated by the availability of some unusual acetylene derivatives. These reactions have led to the creation of novel carbocyclic and heterocyclic compounds. Historically, most of the studies were performed by, or with the participation of, Russian researchers. The cycloaddition reactions include various pathways to cyclobutene and cyclohexadiene derivatives, the heterocyclization reactions have demonstrated additional pathways to various nitrogen‐ and sulfur‐containing heterocycles. The [2+2] cycloaddition of acetylenes with alkenes remains to be the main pathway to cyclobutene derivatives. Another route to cyclobutenes is [2+2] cyclization of 1,3‐butadienes. Normally the focus of this reaction goes back to the synthesis of 1,3‐dienes, but in the case of bulky substituents, formation of cyclobutenes 4.987 are preferred. Acetylenic compounds are widely used in heterocyclization reactions. However, the reactions of electron‐deficient acetylenes leading to the formation of heterocyclic compounds are considered here.