J Org Chem. 2019 Apr 5;84(7):3793-3800. doi: 10.1021/acs.joc.8b02823. Epub 2019 Feb 19.
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.
首次发现，1,2-二甲基-3-乙基碘化咪唑（1a）在与醛反应时，可催化 DBU（1,8-二氮杂双环[5.4.0]十一-7-烯）或 DBN（1,5-二氮杂双环[4.3.0]壬-5-烯）中环酰胺系统的开环反应。这里提出的反应机理涉及 N-杂环烯烃（NHO）催化物种，它作为亲核试剂促进环状酰胺环的开环。得到的ε-己内酰胺和γ-内酰胺衍生亚胺以中等至优异的收率（28-99%）获得，并通过硼氢化钠还原为相应的胺。通过单晶 X 射线衍射研究证实了亚胺产物的存在。
