(11) Sharts, CM; Sheppard, WA Org. React. 1974, 21, 125.(12) Yemul, SS; Kagan, HB Tetrahedron Lett. 1980, 277.(13) Insoluble cross-linked polystyrene4vinylpyridhe complex with boron trifluoride waa prepared by paesing boron trifluoride through a suspension of polystyrene-4-vinylpyridme containing 2% pyridine rings. The polymeric complex contains 1.04% boron.(14) Nafion is a registered trademark of the Du Pont Co., whom we thank for ...