Stereocontrolled Synthesis of 1,5-Stereogenic Centers through Three-Carbon Homologation of Boronic Esters†
Phillip J. Unsworth
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
Search for more papers by this authorDr. Daniele Leonori
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
Search for more papers by this authorCorresponding Author
Prof. Varinder K. Aggarwal
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)Search for more papers by this authorPhillip J. Unsworth
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
Search for more papers by this authorDr. Daniele Leonori
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
Search for more papers by this authorCorresponding Author
Prof. Varinder K. Aggarwal
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS (UK)Search for more papers by this authorWe thank the EPSRC-funded Bristol Chemical Synthesis Doctoral Training Centre for a Ph.D. studentship (P.J.U.) and Inochem-Frontier Scientific for their generous donation of boronic acids and esters. We thank the EPSRC (EP/I038071/1) and the European Research Council (FP7/2007–2013, ERC grant no. 246785) for financial support.
Graphical Abstract
Three more: The 3C homologation of chiral pinacol boronic esters gives di- or trisubstituted allylic boronic esters with high yield and E selectivities. The combination of this method with lithiation–borylation enables the synthesis of alkyl chains that bear 1,5-stereogenic centers. The utility of the process was demonstrated in a formal synthesis of (+)-jasplakinolide.
Abstract
Allylic pinacol boronic esters are stable toward 1,3-borotropic rearrangement. We developed a PdII-mediated isomerization process that gives di- or trisubstituted allylic boronic esters with high E selectivity. The combination of this method with lithiation–borylation enables the synthesis of carbon chains that bear 1,5-stereogenic centers. The utility of this method has been demonstrated in a formal synthesis of (+)-jasplakinolide.
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