N-Heterocyclic Olefin Catalysis for the Ring Opening of Cyclic Amidine Compounds: A Pathway to the Synthesis of ϵ-Caprolactam- and γ-Lactam-Derived Amines

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For the first time, 1,2-dimethyl-3-ethylimidazolium iodide (1a) catalyzes the ring opening of the bicyclic amidine system of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or DBN (1,5-diazabicyclo[4.3.0]non-5-ene) on reaction with aldehydes. The mechanism here proposed involves an N-heterocyclic olefin (NHO) catalytic species that acts as a nucleophile to promote the cyclic amidine ring opening. The resulting ϵ-caprolactam- and γ-lactam-derived imines were obtained in moderate to excellent yields (28-99%) and reduced to the corresponding amines by sodium borohydride. Confirmation of the imine product was achieved via single-crystal X-ray diffraction studies.

Original languageEnglish
Pages (from-to)3793-3800
Number of pages8
JournalJournal of Organic Chemistry
Issue number7
Publication statusPublished - 5 Apr 2019


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