A Highly Regio- and Stereoselective Nickel-Catalyzed Ring-Opening Reaction of Alkyl- and Allylzirconium Reagents to 7-Oxabenzonorbornadienes

• Published in: Journal of organic chemistry 2005-11, Vol.70 (23), p.9545-9550
• Main Authors: Wu, Ming-Si, Jeganmohan, Masilamani, Cheng, Chien-Hong
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed benzenic and aromatic compounds; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Kinetics and mechanisms; Organic chemistry; Preparations and properties; Reactivity and mechanisms
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo051660v

An efficient method for the synthesis of cis-2-alkyl- or allyl-1,2-dihydronaphthalenes via a nickel-catalyzed highly regio- and stereoselective ring-opening addition of alkyl- or allylzirconium reagents to 7-oxabenzonorbornadienes is described. Treatment of 7-oxabenzonorbornadienes 1a−c with various alkylzirconium reagents 2a−j (Cp2ZrClCH2CH2R:  R = tert-butyl, n-butyl, n-pentyl, −(CH2)3CHC(CH3)2, −SiMe3, −CH2SiMe3, −(CH2)3Br, cyclopentyl, cyclohexyl, and benzyl) in the presence of NiBr2(dppe) and Zn powder in dry THF at 50 °C afforded the corresponding cis-2-alkyl-1,2-dihydronaphthalene derivatives 3a−m in good yields. In addition, allyl zirconium reagents 4a−c also underwent ring-opening reactions with 1a and 1c to give 5a−d in very good yields. The alkylative ring-opening products from 7-oxabenzonorbornadiene can be further converted to naphthalene derivatives 6a−c, via an acid-mediated dehydration, in good to excellent yields. A possible mechanism for the present catalytic reaction was proposed.