B,B-dihaloterpenylboranes as reagents for the diastereo- and enantioselective synthesis of syn-aldols

Article abstract of DOI:10.1016/S0957-4166(97)00138-9

A series of known and new B,B-dihaloterpenylboranes, readily synthesized from the corresponding terpenes, were examined for the diastereo- and enantioselective synthesis of syn-aldols. Thus, IpcBCl₂, EapBCl₂, LgfBCl₂, cis-MyrBCl₂, 2-IcrBCl₂', 4-IcrBCl₂, and 2-IcrBBr₂ in the presence of i-Pr₂NEt, convert 3-pentanone to ≤99% Zenolates, converted by aldehydes to pure syn-aldols in 7-74% enantiomeric excess (ee). The most efficient of these reagents, B,B-dibromo-2-isocaranylborane, was tested for the enolboration of 3-pentanone, followed by aldolization with a series of aldehydes.