Highly stereoselective approach to alk-2-yne-1,4-diols by oxazaborolidine-mediated reduction of alk-2-yne-1,4-diones.
We performed the borane-mediated reduction of a series of symmetrical alk-2-yne-1,4-diones (5) in the presence of the oxazaborolidine (R)-6 to afford (R,R)-alk-2-yne-1,4-diols ((R,R)-1) in good yields and high stereoselectivities (up to 99.9% ee). In some cases, the stereochemical purity of 1 was improved by a two-step process: (i) temporary transformation of 1 into its vic-dibromo derivatives 9, which allowed us to remove the minor meso isomer by chromatography, and (ii) regeneration of the enantioenriched diols 1 with SmI2. Reduction of the hexacarbonyldicobalt complexes 8 derived from 5 was also successful.
Departament de Química Orgànica, Universitat de Barcelona, C/Martí i Franquès 1-11, E-08028 Barcelona, Catalonia, Spain.
Xavier
X
Ariza
Jordi
J
Bach
Ramon
R
Berenguer
Jaume
J
Farràs
Montserrat
M
Fontes
Jordi
J
Garcia
Marta
M
López
Jordi
J
Ortiz