Enantioselective Synthesis of 1,5-anti- and 1,5-syn-Diols Using a Highly Diastereoselective One-Pot Double Allylboration Reaction Sequence

Eric M. Flamme and William R. Roush*
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055
J. Am. Chem. Soc., 2002, 124 (46), pp 13644–13645
DOI: 10.1021/ja028055j
Publication Date (Web): October 26, 2002
Copyright © 2002 American Chemical Society
*

 To whom correspondence should be addressed. E-mail:  roush@umich.edu.

Abstract

Abstract Image

Highly diastereo- and enantioselective syntheses of 1,5-disubstituted (E)-1,5-anti-pent-2-endiols 1 and (Z)-1,5-syn-pent-2-endiols 2 have been achieved via the one-pot coupling of two different aldehydes with either (E)-γ-(1,3,2-dioxaborinanyl)-allyl]diisopinocampheylborane (4) or (E)-γ-(4,4,5,5-tetraphenyl-1,3,2-dioxaborolanyl)allyl]diisopinocampheylborane (11), respectively. The indicated diols 1 and 2 are obtained in 63−95% yield with 89−96% ee and ≥20:1 diastereoselectivity in all cases. The bifunctional γ-boryl-substituted allylborane reagents 4 and 11 were generated in situ by the hydroboration of allenes 3 and 10 with diisopinocampheylborane. The keys to the success of this method are the excellent stereocontrol in the allylboration step leading to 5 and the corresponding substituted methallylboronate derived from 11, the stereospecificity of the subsequent allylboration reaction of the substituted methallylboronate intermediates, and the ability of the diol auxiliary to induce equatorial or axial placement of the substituent α to boron in transition states 7 and 8.

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History

  • Published In Issue November 20, 2002
  • Received August 8, 2002

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