Enantioselective Cyclobutenylation of Olefins Using <i>N</i>-Sulfonyl-1,2,3-Triazoles as Vicinal Dicarbene Equivalents
Sajan C. Patel, Myles W. Smith, Jaron A. M. Mercer, Kensuke Suzuki, Noah Z. Burns
Abstract
Cyclobutenes are highly useful synthetic intermediates as well as important motifs in bioactive small molecules. Herein, we report a regio-, chemo-, and enantioselective synthesis of cyclobutenes from olefins using N-sulfonyl-1,2,3-triazoles as vicinal dicarbene equivalents or alkyne [2 + 2] cycloaddition surrogates. Terminal and cis-olefins can be transformed into enantioenriched cyclopropanes via rhodium catalysis. Then, in one pot, treatment of these intermediates with tosyl hydrazide and base effects diazo formation followed by rhodium-catalyzed ring expansion to yield enantioenriched cyclobutenes. These cyclobutenes can be transformed into highly substituted, enantioenriched cyclobutanes, including structures relevant to natural product scaffolds.