Bi(OTf) 3 ‐Catalyzed Diastereoselective S N 1‐Type Reactions of Chiral Propargylic Acetates

Stereoelectronic factors are apparently responsible for the high selectivity observed in the title S N 1‐type reaction of acetates 1 in favor of the anti products 2 . The preferred conformation of the intermediate propargylic cations would lead to the syn product; however, a second conformation exists, in which the tert ‐butyl group adopts an antiperiplanar orientation with respect to the incoming nucleophile. Tf=trifluoromethanesulfonyl, TMS=trimethylsilyl.