期刊
ADVANCED SYNTHESIS & CATALYSIS
卷 352, 期 2-3, 页码 499-518出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adsc.200900686
关键词
N-acyliminuim ion cyclization; alkaloids; one-pot reaction; organocatalysis; quinolizidines; stereodivergent synthesis
资金
- Swedish Research Council
- Royal Swedish Academy of Science
- Carl Trygger Foundation for Scientific Research
A diverse stereodivergent organocatalytic one-pot addition/cyclization/annulation sequence to optically active quinolizidine derivatives from easily available starting materials is presented. The one-pot sequence relies on a pyrrolidine-catalyzed enantioselective Conjugate addition of electron-deficient amide alpha-carbons to alpha,beta-unsaturated aldehydes, spontaneous hemiaminal formation and acid-catalyzed/mediated N-acyliminium ion cyclization to give the quinolizidine framework. Simple tuning of the reaction conditions in the N-acyliminuim ion cyclization step provides a diastereomeric switch, which gives access to both of the two bridgehead epimers through kinetic, thermodynamic or chelation control. The methodology display a broad substrate scope that is demonstrated by the stereoselective formation of indolo-, thieno-, benzofuro-, furo- and different benzoquinolizidine derivatives with high atom efficiency, up to >99% ee and up to >95:5 dr. Due to its efficiency, synthetic diversity and operational simplicity, this protocol has the potential to find important use as a key step in natural product Synthesis, biochemistry and pharmaceutical science. The stereochemical Outcome of the one-pot sequence was investigated. and the mechanism and origin of stereoselectivity of the different steps is discussed.
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