Camphorsulfonic acid: A versatile and useful reagent in organic synthesis

Abstract

(A) CSA is used in the preparation of hypervalent iodine reagents. These reagents have been used frequently in organic chemistry especially in synthesis. Since these are nonmetallic oxidation agents, toxicity of many transition metals commonly involved in such process is avoided.6 (Chemical Equation Presented) (B) Sulfonamides belong to an important class of pharmaceutical compounds exhibiting a broad wide variety of biological activities. Recently, a novel approach for the synthesis of alkyl and aryl sulfonamides was reported with excellent yields and moderate conditions, consisting on the reaction of CSA, isocyanides and water in dichloromethane at room temperature.7 (Chemical Equation Presented) (C) Putrescine, spermidine and spermine are essencial polyamines for the growth and function of normal cells. (S)-CSA was used on the resolution of 2-piperidineethanol, a chiral starting material for the asymmetric synthesis of (-)-isooncinotine, a 22-membered lactam of spermidine alkaloid.8 (Chemical Equation Presented) (D) D-CSA, a chiral Brønsted acid, revealed to be a practical and efficient catalyst for the enantioselective Michael-type Friedel-Crafts reactions of indoles with aromatic enones, affording the corresponding β-indolyl ketones with excellent yields and moderate enantioselectivities. 9 (Chemical Equation Presented) (E) The enantioselective Henry (nitroaldol) reaction between nitromethane and an aromatic aldehyde was successfully catalyzed by copper complexes of chiral iminopyridine, prepared from CSA. High yield and good enantioselectivity were achieved.10 (Chemical Equation Presented) (F) L-Proline-catalyzed aldol reactions were promoted by a catalytic amount of chiral ionic liquid based on CSA with good chemoselectivity in water as well as in organic solvents.11 (Chemical Equation Presented) (G) Recently, considerable attention has been devoted to active polyanilines (PAn's) due to their potential applications in areas like chiral sensors, electrochemical asymmetric synthesis and chiral separations. (S)-CSA has been used as a chiral acid during oxidative polymerization of aniline, in order to induce the optical activity of polyaniline emeraldine salts (PAn·HA).12 (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.