Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Main Authors: Ruben Pomar Fuentespina, José Angel Garcia de la Cruz, Gabriel Durin, Victor Mamane, Jean-Marc Weibel, Patrick Pale
• Format: Article
• Language: English
• Published: Beilstein-Institut 2019-06-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: boron; enyne; lithium; oxirane; rearrangement
• Online Access: https://doi.org/10.3762/bjoc.15.141

1,3-Enynes are important building blocks in organic synthesis and also constitute the key motif in various bioactive natural products and functional materials. However, synthetic approaches to stereodefined substituted 1,3-enynes remain a challenge, as they are limited to Wittig and cross-coupling reactions. Herein, stereodefined 1,3-enynes, including tetrasubstituted ones, were straightforwardly synthesized from cis or trans-alkynylated oxiranes in good to excellent yields by a one-pot cascade process. The procedure relies on oxirane deprotonation, borylation and a stereospecific rearrangement of the so-formed alkynyloxiranyl borates. This stereospecific process overall transfers the cis or trans-stereochemistry of the starting alkynyloxiranes to the resulting 1,3-enynes.