Practical and efficient methods for sulfonylation of alcohols using Ts(Ms)Cl/Et3N and catalytic Me3N•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.