Accession Number : ADA193193

Title :   Enantioselective Ring-Cleavage of meso- Epoxides with beta-Halodiisopinocampheylboranes.

Descriptive Note : Technical rept.,

Corporate Author : PURDUE UNIV LAFAYETTE IN

Personal Author(s) : Joshi, N N r ; Srebnik, M ; Brown, Herbert C

PDF Url : ADA193193

Report Date : 26 Apr 1988

Pagination or Media Count : 11

Abstract : B-Halodiisopinocampheylboranes, IpcBX, in particular the bromide 1b, and the Iodide 1c, differentiate between the enantiotopic carbon-oxygen bonds of meso-epoxides to furnish 1,2-halohydrins of moderate to excellent enantiomeric purity. Thus (-)-(1R, 2R)-2-bromocyclohexanol, (-)-(1R, 2R)-2-iodocyclohexanol, (-)-(1R, 2R)-2-iodocyclohex-4-en-1-o1 and (-)-(1R, 2R)-2-bromocyclohex-4-en-1-o1 are obtained in 84%, 91%, 63% and 95% ee respectively from the corresponding meso-epoxides and haloborane reagents. Simple recrystallization from pentane then gives halohydrins of essentially 100% ee; cis-2-butene oxide and cis-3-hexene oxide furnish the corresponding (1R, 2R)-iodohydrins in 78 and 69% ee respectively. In all cases the S carbon of the meso-epoxide is selectively cleaved. This is the first example of enantioselective ring cleavage of meso-epoxides to obtain optically active 1,2-halohydrins. Keywords: Asymmetric synthesis.

Descriptors :   *EPOXY COMPOUNDS, *HALOHYDRINS, *SYNTHESIS, *BORANES, ASYMMETRY, CARBON, RECRYSTALLIZATION, CHEMICAL BONDS, CLEAVAGE, CYCLIC COMPOUNDS, OXYGEN, STEREOCHEMISTRY

Subject Categories : Organic Chemistry
      Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE