DBU as a Nucleophilic Agent in the Reactions with Nitrile Imines

Abstract 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) has gained widespread popularity in recent decades and is used as a mild catalyst and reagent in many organic chemistry processes, including elimination, esterification, Mannich-type reactions, cyclizations, condensation reactions, and many others. DBU is also considered as a base in 1,3-dipolar cycloaddition reactions in which reactive dipoles are formed in situ as a result of dehydrohalogenation of the stable precursors. It was found in this work that the generation of nitrile imines from hydrazonoyl halides using DBU demonstrated lower yields of cycloadditions than with triethylamine. A possible explanation for the lower yield may be nucleophilic substitution of a chlorine atom in hydrazonoyl chlorides to DBU fragment. Despite the fact that the properties of nucleophilic catalysts for DBU are known, a similar result for nitrile imines has been described for the first time.