Enantioselective Synthesis of Cyclopropanone Equivalents and Application to the Formation of Chiral β-Lactams.

Cyclopropanone derivatives have long been considered unsustainable synthetic intermediates due to their extreme strain and kinetic instability. Herein, we report the enantioselective synthesis of 1-sulfonylcyclopropanols as stable yet powerful equivalents of the corresponding cyclopropanone derivatives, via α-hydroxylation of sulfonylcyclopropanes using a bis(silyl) peroxide as electrophilic oxygen source. This work constitutes the first general approach to enantioenriched cyclopropanone derivatives. Both the electronic and steric nature of the sulfonyl moiety, which serves as a base-labile protecting group and confers crystallinity to these cyclopropanone precursors, were found to have a crucial impact on the rate of equilibration to the corresponding cyclopropanone, highlighting their modular nature and the potential for their widespread adoption as synthetic intermediates. The utility of these cyclopropanone surrogates is demonstrated in a mild and stereospecific formal [3+1] cycloaddition with simple hydroxylamines acting here as nitrene equivalents, leading to the efficient formation of chiral β-lactam derivatives.