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)。