Asymmetric Synthesis Using the Bis(2,4-dimethyl-3-pentyl)-(L)-tartrate Esters of Substituted Allylboronic Acids. Synthesis of α,β-Disubstituted Tetrahydropyrans and  Tetrahydrofurans.

Herbert C. Brown; Avinash S. Phadke

doi:10.1055/s-1993-22655

Synlett 1993; 1993(12): 927-928
DOI: 10.1055/s-1993-22655

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Asymmetric Synthesis Using the Bis(2,4-dimethyl-3-pentyl)-(L)-tartrate Esters of Substituted Allylboronic Acids. Synthesis of α,β-Disubstituted Tetrahydropyrans and Tetrahydrofurans.

Herbert C. Brown^* , Avinash S. Phadke

^*H. C. Brown and R. B. Wetherill Laboratories of Chemistry, Purdue University, West Lafayette, Indiana 47907 U.S.A.

Abstract

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A highly useful application of allylboration for the synthesis of optically pure α,β-disubstituted tetrahydropyrans and tetrahydrofurans is described. The allylboronate esters 4, easily prepared by esterification of allylboronic acids 3 with bis(2,4-dimethyl-3-pentyl)-(L)-tartrate, readily undergo smooth reaction with representative aldehydes at -100 °C to afford the corresponding halohydrins 5. These are readily cyclized with sodium hydride in the presence of dimethyl sulfoxide to give the cyclic ethers 6 in good yields (70-80%) and in excellent enantiomeric excesses (83-98%).

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