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Brønsted or Lewis Acid Initiated Multicomponent Cascade Reaction: Diastereoselective Synthesis of Imidazolidinyl Spirooxindole Derivatives
Author(s) -
Zhang JunQi,
Qi ZhengHang,
Yin ShaoJie,
Li HaiYan,
Wang Yong,
Wang XingWang
Publication year - 2016
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201600560
Subject(s) - chemistry , trifluoromethanesulfonate , diazo , catalysis , oxindole , lewis acids and bases , brønsted–lowry acid–base theory , medicinal chemistry , cascade reaction , catalytic cycle , combinatorial chemistry , stereochemistry , organic chemistry
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⋅H 2 O) 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‐1 H ‐1,2,3‐triazole intermediate. Subsequently, the releasing of N 2 is the rate‐limiting step of the whole catalytic cycle.