Addition Stereoselective, nonchelation-controlled
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
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 products 7 and 36, respectively (stereoselectivity 95:5, 86:14). These results provide a route to oligo(tetrahydrofuran)s with the relative stereochemistry trans-syn-cis. A stereodirecting effect of the chiral center in the organozinc reagent 17 is found, leading to simple diastereoselectivies in the reaction with achiral aldehydes and to a matched-mismatched case in the reaction with the chiral aldehyde 1.
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