A. Avenoza, M. P. Bueno, C. Cativiela and J. A. Mayoral, “Asymmetric Synthesis of Exo-Norbornane-2-carboxylic Acids,” Tetrahedron: Asymmetry, Vol. 3, No. 3, 1992, pp. 343-346. doi:10.1016/S0957-4166(00)80270-0

has been cited by the following article:

• TITLE: Stereo-Selective Synthesis of 5-Norbornene-2-exo-carboxylic Acid—Rapid Isomerization and Kinetically Selective Hydrolysis

  AUTHORS: Miki Kanao, Atsushi Otake, Kousuke Tsuchiya, Kenji Ogino

  KEYWORDS: Stereo-Selective Synthesis; 2-Substituted Norbornene; Isomerization; Kinetically Selective Hydrolysis

  JOURNAL NAME: International Journal of Organic Chemistry, Vol.2 No.1, March 15, 2012

  ABSTRACT: Simple and efficient stereo-selective synthesis of exo-5-norbornene-2-carboxylic acid (NBCA) is reported. Preliminary studies on base promoted isomerization of methyl 5-norbornene-2-carboxylate (MNBC) revealed that rapid isomerization was accomplished with sodium tert-butoxide (tBuONa), and the exo-content at the equilibrium was ca. 60%. The hydrolyses of endo-rich MNBC (endo/exo = 80/20) under various conditions were carried out. The exo selectivity for resulting NBCA was improved when the hydrolysis was conducted with equimolar water at room temperature in the presence of the stronger base (tBuONa) (endo/exo: 18/82). Whereas the use of excess amount of water led to rapid and non-selective hydrolysis affording high endo content of the product. The plausible reaction mechanism involving rapid equilibrium of thermodynamic isomerization and kinetically preferred hydrolysis of exo ester is proposed.