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Highly Diastereoselective Allylic Azide Formation and Isomerization. Synthesis of 3(2‘-Amino)-β-lactams

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posted on 17.02.2005, 00:00 by Giuliana Cardillo, Serena Fabbroni, Luca Gentilucci, Rossana Perciaccante, Fabio Piccinelli, Alessandra Tolomelli
The stereoselective anti SN2‘ attack of NaN3 to 3-alkenyl-3-bromo-azetidin-2-ones gave a mixture of diastereomeric azides in fast equilibrium. The [3,3]-sigmatropic rearrangement of allylic azides occurred with complete stereocontrol, allowing the equilibrium to be directed preferentially toward the (E)- or (Z)-isomer, useful precursors of 3(2‘-amino)-β-lactams.