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