Synthetic Utility of Vinyl MIDA Boronate

By: Josephine Nakhla, ChemFiles Volume 9 Article 1

The utility of vinyl MIDA boronate was demonstrated via cyclopropanation and epoxidation to the corresponding MIDA cyclopropane and oxirane, respectively. These procedures (Scheme 13) provided air and chromatography-stable solids in both cases, with the oxirane being the first known synthesis of an unsubstituted oxiranylborane (confirmed by X-ray analysis of the oxiranylborane).

Scheme 13(697311)(703478)

Vinyl MIDA boronate was also successfully subjected to Heck and oxidative Heck reactions as well as to olefin metathesis (Scheme 14) to provide the desired alkenyl MIDA boronates. The cross metathesis of vinyl MIDA boronate with various olefins represents a potent strategy for the highly stereoselective construction of substituted vinyl boranes. This method proved successful in the preparation of a variety of disubstituted olefins (Scheme 15) with excellent yields (81-98%) and E:Z selectivities (>20:1). This procedure represents a significant advance relative to the cross metathesis with alkenyl pinacol, which can be limited by instability of the alkenyl boronic ester substrates, the stereoselectivity of the transformation, and/or the ease of purification of the resulting products.1

Scheme 14(703478)(699292)

Scheme 15

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Materials

     

References

  1. Uno, B. E.; Gillis, E. P.; Burke, M. D. Tetrahedron 2008, In Press.

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