STEREOSELECTIVE ADDITIONS OF CHIRAL, FUNCTIONALIZED ORGANOZINC REAGENTS TO ACHIRAL AND CHIRAL ALDEHYDES - A MATCHED-MISMATCHED CASE IN ORGANOZINC CHEMISTRY

The additions of the enantiomerically pure organozinc reagents 17 and 33 to the THF-aldehyde 1 in the presence of the monodentate Lewis acid boron trifluoride-ether give the nonchelation-controlled addition pro ducts 7 and 36, respectively (stereoselectivity 95:5, 86:14). These re sults provide a route to oligo(tetrahydrofuran)s with the relative ste reochemistry trans-syn-cis. A stereodirecting effect of the chiral cen ter in the organozinc reagent 17 is found, leading to simple diastereo selectivies in the reaction with achiral aldehydes and to a matched-mi smatched case in the reaction with the chiral aldehyde 1.