1,3-Dipolar Cycloaddition of Diazoalkanes to (<i>S</i>)-(+)-3-[(4-Methylphenyl)sulfinyl]-5,6-dihydropyran-2-one. Synthesis of Optically Pure Cyclopropanes by Denitrogenation of Sulfinyl and Sulfonyl Pyrazolines
作者:David Cruz Cruz、Francisco Yuste、M. Rosario Martín、Amelia Tito、José L. García Ruano
DOI:10.1021/jo900525s
日期:2009.5.15
give the pyrazolines 5 and 7-exo. The denitrogenation of optically pure sulfinyl pyrazolines 4−7-exo into the corresponding cyclopropanes with Yb(OTf)3 occurred with complete retention of configuration but moderate chemoselectivity and yields. These results were significantly improved starting from sulfonyl pyrazolines, which afforded optically pure 3-oxabicyclo[4.1.0]heptan-2-ones with yields ranging
将重氮甲烷和重氮乙烷加至对映体(S)-(+)-3-[(4-甲基苯基)亚磺酰基] -5,6-二氢吡喃-2-酮(3)中,得到相应的吡唑啉4和6 - exo良好且具有几乎完全的π面选择性。当在Yb(OTf)3存在下进行反应时,将面部选择性反转以得到吡唑啉5和7 - exo。光学纯的亚磺酰基吡唑啉的脱氮4 - 7 -外切成相应的环丙烷有Yb(OTF)3发生时完全保留构型,但化学选择性和产率中等。从磺酰基吡唑啉开始,这些结果得到了显着改善,磺酰吡唑啉提供了光学纯的3-氧杂双环[4.1.0]庚烷-2-酮,产率在65%(17和ent - 17)和≥95%(16和ent - 16)之间)。