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

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...

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Bibliographic Details
Published in:Journal of organic chemistry 2019-04, Vol.84 (7), p.3793-3800
Main Authors: Peixoto, Daniela, Malta, Gabriela, Cruz, Hugo, Barroso, Sónia, Carvalho, Ana Luísa, Ferreira, Luísa M, Branco, Paula S
Format: Article
Language:English
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Summary: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.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.8b02823