Practical and efficient methods for sulfonylation of alcohols using Ts(Ms)Cl/Et3N and catalytic Me3H·HCl as combined base: Promising alternative to traditional pyridine
Several alcohols were smoothly and practically tosylated by two methods A and B. Method A uses the TsCl/Et3N (1.5-2.5 equiv)/cat. Me3N . HCl (0.1-1.0 equiv) reagent. Compared with the traditional qr-solvent method, the method A has merits of its much higher reaction rate, operational simplicity, economy in the use of the amine, and circumvention of the undesirable side reaction from R-OTs to R-CL Method B uses TsCl/KOH [or Ca(OH)(2)]/cat. Et3N (0.1 equiv)/cat. Me3N . HCl (0.1 equiv) as the reagent, which will be suited for practical and large scale production for primary alcohols. On both methods A and B, a clear joint action of Et3N and Me3N . HCl catalysts was observed. H-1 NMR measurements support the proposed mechanism of the catalytic cycle. Related methanesulfonylation using Et3N and cat. Me3N . HCl in toluene solvent also successfully proceeded, wherein he clear joint action was also observed. (C) 1999 Elsevier Science Ltd. All rights reserved.
Facile and Practical Methods for the Sulfonylation of Alcohols Using Ts(Ms)Cl and Me2N(CH2)nNMe2 as a Key Base
作者:Yoshihiro Yoshida
DOI:10.1055/s-1999-3561
日期:1999.9
General, Robust, and Stereocomplementary Preparation of β-Ketoester Enol Tosylates as Cross-Coupling Partners Utilizing TsCl−<i>N</i>-Methylimidazole Agents
(Z)-stereocomplementary enol tosylation of beta-ketoesters using TsCl- N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl-NMI-Et3N. beta-Ketoesters underwent (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH (total