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

Article abstract of DOI:10.1016/S0040-4020(99)00002-2

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 Py-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. ¹H 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 the clear joint action was also observed.