Organic Letters 2006-10-12

Stereochemical control in the reduction of 2-chromanols.

Kelin Li, Kumar Vanka, Ward H Thompson, Jon A Tunge

Index: Org. Lett. 8 , 4711, (2006)

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Abstract

[reaction: see text] Reduction of C5-substituted 2-hydroxychromans selectively provides 2,4-cis-chromans using large silane reductants and 2,4-trans-chromans using the smaller silane PhSiH(3). The stereochemical outcome has been rationalized on the basis of a Curtin-Hammett kinetic situation arising from hydride delivery to two different conformations of an intermediate oxocarbenium ion. This method provides a powerful way to control the relative stereochemistry of these substructures which are prevalent in bioactive natural products.