Jun-Qi Zhang, Zheng-Hang Qi, Shao-Jie Yin, Hai-Yan Li, Yong Wang*（王勇）, and Xing-Wang Wang*（王兴旺）
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science Soochow University ,Suzhou 215123 (P.R. China)
ChemCatChem 2016, 8, 2797 – 2807
One peculiar type of aza-hetero-imidazolidinyl spirooxindole derivatives was efficiently constructed by the three-component [2+2+1] cascade reaction of 1,4-oxazepines with diazo-oxindoles. Iron(II) trifluoromethanesulfonate [Fe(OTf)2] or p-toluenesulfonic acid monohydrate (p-TsOH⋅H2O) proved to be optimal catalysts for this transformation, providing the desired products in high yields (up to 94 %) with excellent diastereoselectivity (up to 99:1 dr). Experimental studies showed that the reaction rate of Brønsted acid catalysis was faster than that of Lewis acids. Furthermore, the mechanism was theoretically investigated for Brønsted acid as the catalyst and a reaction pathway was proposed. DFT calculations suggested that the diazo-oxindole can act as a 1,3-dipole to add to a C=N double bond of 1,4-oxazepine, which forms a 4,5-dihydro-1H-1,2,3-triazole intermediate. Subsequently, the releasing of N2 is the rate-limiting step of the whole catalytic cycle.
链接：http://onlinelibrary.wiley.com/doi/10.1002/cctc.201600560/full
