AgOTf

AgOTf, Mel, 2,6-di-f-butylpyridine, 39-96% yield. This method can be used to prepare alkyl, benzyl, and allyl ethers. ... 

In the Koenigs-Knorr method and in the Helferich or Zemplen modifications thereof, a glycosyl halide (bromide or chloride iodides can be produced in situ by the addition of tetraalkylammonium iodide) is allowed to react with a hydrox-ylic compound in the presence of a heavy-metal promoter such as silver oxide, carbonate, perchlorate, or mercuric bromide and/or oxide,19-21 or by silver triflu-oromethanesulfonate22 (AgOTf). Related to this is the use of glycosyl fluoride donors,23 which normally are prepared from thioglycosides.24... 

An interesting intramolecular Friedel-Crafts-type cyclization was developed by Pericas et al. Thus, aryl glycidyl ethers reacted to 3-chromanols as the only reaction product when treated with a catalytic amount of FeBr3 in the presence of AgOTf in CH2CI2 at room temperature (Scheme 9) [26]. The addition of a silver salt proved to... 

By following the reported procedure, coupling reaction of 70 and 2,3,4-tri-O-acetyl-a-L-arabinopyranosyl bromide in the presence of AgOTf and tetramethy-lurea (TMU) gave the coupled product (72) in 73% yield. Finally, treatment of 72 with K2CO3 in MeOH provided the synthetic phenethyl 6-O-a-L-arabinopyranosyl-p-D-glucopyranoside (66) in 86% yield. 

The coupling reaction of 78 with 2 equivalents of the reported 2,3,4-tri-O-benzoyl-a-L-rhamnopyranosyl bromide in the presence of AgOTf and TMU in CH2CI2 gave the coupled product (81) in 56% yield. Finally, treatment of 81 with NaOMe in MeOH-THF provided the synthetic (3Z)-hexenyl 6-O-a-L-rhamnopyranosyl-p-D-gluco-pyranoside (76) in 96% yield. 

Finally, intramolecular hydroamination/cyclisation of M-alkenyl ureas was catalysed by the well-defined [AuCl(IPr)] complex (Schane 2.16), in the presence of AgOTf (5 mol%, rt, methanol, 22 h). The cationic Au(lPr)+ is presumably the active species [83]. 

Intermolecular hydroalkoxylation of 1,1- and 1,3-di-substituted, tri-substituted and tetra-substituted allenes with a range of primary and secondary alcohols, methanol, phenol and propionic acid was catalysed by the system [AuCl(IPr)]/ AgOTf (1 1, 5 mol% each component) at room temperature in toluene, giving excellent conversions to the allylic ethers. Hydroalkoxylation of monosubstituted or trisubstituted allenes led to the selective addition of the alcohol to the less hindered allene terminus and the formation of allylic ethers. A plausible mechanism involves the reaction of the in situ formed cationic (IPr)Au" with the substituted allene to form the tt-allenyl complex 105, which after nucleophilic attack of the alcohol gives the o-alkenyl complex 106, which, in turn, is converted to the product by protonolysis and concomitant regeneration of the cationic active species (IPr)-Au" (Scheme 2.18) [86]. 

The intermolecular hydration of allenes catalysed by [AuCl(lPr)]/AgOTf (1 1,5 mol%) in dioxane/waler at room temperature, has also been studied. In most cases, low to modest yields (25-65%) of fi-aUylic alcohols were obtained by selective addition of the water to the terminal C atom of the aUene group [89]. 

Recently, Caddick and Cloke have developed an extension of this procedure that allows the use of alkyl bromides as coupling partners. The basic changes consist of a stoichiometric amount of the bulkier KO Bu instead of KOMe to activate the borane, and the addition of AgOTf to the reaction mixture [119]. These results, although poor in terms of yield, clearly confirm that sp -sp Suzuki-Miyaura cross-couplings are possible and should be further developed (Scheme 6.35). 

PdCOTfj CIPr) generated in situ from [Pd(p,-Cl)(Cl)(IPr)]j and AgOTf was reported to catalyse the copper-free Wacker-type oxidation of styrene derivatives using ferf-butyl hydroperoxide (TBHP) as the oxidant (Table 10.7) [41]. Reaction conditions minimised oxidative cleavage of styrene, which is a common side-reaction in Wacker-type oxidations. However, when franx-stilbene was used as a substrate, a significant amount of oxidative cleavage occurred. 

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