期刊
CHEMCATCHEM
卷 8, 期 17, 页码 2797-2807出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cctc.201600560
关键词
acidity; density functional calculations; diazo compounds; iron; spiro compounds
资金
- National Natural Science Foundation of China [21272166, 21572150]
- Major Basic Research Project of the Natural Science Foundation of the Jiangsu Higher Education Institutions [13KJA150004]
- Program for New Century Excellent Talents in University [NCET-12-0743]
- Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
- National Key Technologies R&D Program of China, CAU [2015BAK45B01]
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 center dot 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 Bronsted acid catalysis was faster than that of Lewis acids. Furthermore, the mechanism was theoretically investigated for Bronsted 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 N-2 is the rate-limiting step of the whole catalytic cycle.
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