Nickel-Catalyzed Highly Stereoselective Ring Opening of 7-Oxa- and Azanorbornenes with Organic Halides

Nickel-catalyzed ring-opening reactions of 7-heteroatom norbornadienes and norbornenes with various organic halides to give products with multiple stereocenters are described. Treatment of 7-oxabenzonorbornadiene (1a) and 7-carbomethoxy-7-azabenzonorbornadiene (1b) with aryl iodides (ArI) in the presence of NiCl2(PPh3)2 and Zn powder gave the corresponding ring-opening addition products cis-1,2-dihydro-2-aryl-1-naphthol (2a−m) and methyl N-[cis-1,2-dihydro-2-aryl-1-naphthyl]carbamate (3a−e) completely stereoselectively in 40−99% yields. The nickel system also catalyzes the reaction of highly substituted oxabicyclic [2.2.1] compounds (1c−e) with organic halides (PhI, PhCH2Br, PhCHCHBr, and PhCBrCH2) to give the corresponding ring-opening products (4a−d, 5, 6a,b) that consist of four fixed stereocenters. Studies on the effect of solvent on the reaction of 1a with PhI show that CH3CN gives the highest yield of product 2a; no product 2a is observed when toluene, dichloromethane, methanol, DMF, or DMSO is used...