Triflate methyl

All lation. In alkylation, the dialkyl sulfates react much faster than do the alkyl haHdes, because the monoalkyl sulfate anion (ROSO ) is more effective as a leaving group than a haHde ion. The high rate is most apparent with small primary alkyl groups, eg, methyl and ethyl. Some leaving groups, such as the fluorinated sulfonate anion, eg, the triflate anion, CF SO, react even faster in ester form (4). Against phenoxide anion, the reaction rate is methyl triflate [333-27-7] dimethyl sulfate methyl toluenesulfonate [23373-38-8] (5). Dialkyl sulfates, as compared to alkyl chlorides, lack chloride ions in their products chloride corrodes and requires the use of a gas instead of a Hquid. The lower sulfates are much less expensive than lower bromides or iodides, and they also alkylate quickly. 

Lithium 4-methylthiazolate and benzothiazolate with [( / -Cp)Fe(CO)2Cl] form the C-coordinated complexes, e.g. 23, which on protonation with triflic acid transform into the carbenes, e.g. 24 (92JCS(D)1009). Isothiazole enters the same chain of reactions but can also be methylated using methyl triflate (94JOM(479)C12). 

The same lithium salts with copper(I) chloride react through the stage of the anionic C-coordinated complexes 100, which on protonation with hydrochloric acid give the corresponding 2,2 -bithiazoles, with triflic acid— the N-coordinated species 101, and on methylation with methyl triflate they give carbenes of structure 102. 

Isothiazole forms the carbenes upon treatment of its lithium salt with [CfiF5Au(THT)] and methyl triflate while the C-coordinated complex formed before methylation was not isolated. When [Ph3PAuCl] is used as the precursor, both C-coordinated complex and then carbene can be prepared (95JCS(D)2067). 

Treatment of 8-azidomethylperhydropyrido[l,2-c]pyrimidin-l-one 157 with methyl triflate and catalytic hydrogenation of the azide group led to the formation of tricyclic guanidine derivative 158 (01JA8851). Hydroxy group of 149 was protected with methoxymethyl chloride, and the p-methoxybenzyl protecting group (PMB) was eliminated by treatment with DDQ. 

From mechanistic view points, as represented in Fig. 3, it is likely that the phosphine oxide is methylated by methyl triflate. The resulting phosphoniiun salt... 

Phosphine-borane 63a (75% ee) was obtained by reduction of compound (Sp)-62a using LDBB at -60°C and nucleophilic substitution with iodomethane in 72 % yield. The observed loss of optical purity may be ascribed to stereomutation of the generated tricoordinated phosphorus species. Recrystallization afforded (S)-63a in > 99% ee. On the other hand, severe racemization was observed using the same method with (Rp)-62b. An alternative strategy consisted of deborana-tion of (Rp)-62b using ZSl-methylpyrrolidine, methylation with methyl triflate. 

Alkyl sulfonates are very effective cationic initiators of e-caprolactone, although only the more reactive methyl triflate and methyl fluorosulfate result in a high conversion. The mechanism of polymerization in the presence of these initiators is believed to involve methylation of the exocyclic carbonyl oxygen, followed by partial ring opening of the activated lactone by the counteranion (Fig. 

Imidazolides can also be activated by N-alkylation with methyl triflate.116 Imidazolides react with alcohols on heating to give esters and react at room temperature with amines to give amides. Imidazolides are particularly appropriate for acylation of acid-sensitive materials. 

Amino-squaraines 39 (Z1 = O, Z2 = R1R2) are synthesized by etherification of the oxo-squaraine oxygen using dimethylsulfate or methyl triflate followed by substitution of the methoxy group with amines [52] (Fig. 10). 

Transformations through 1,2-addition to a formal PN double bond within the delocalized rc-electron system have been reported for the benzo-l,3,2-diazaphospholes 5 which are readily produced by thermally induced depolymerization of tetramers 6 [13] (Scheme 2). The monomers react further with mono- or difunctional acyl chlorides to give 2-chloro-l,3,2-diazaphospholenes with exocyclic amide functionalities at one nitrogen atom [34], Similar reactions of 6 with methyl triflate were found to proceed even at room temperature to give l-methyl-3-alkyl-benzo-l,3,2-diazaphospholenium triflates [35, 36], The reported butyl halide elimination from NHP precursor 13 to generate 1,3,2-diazaphosphole 14 upon heating to 250°C and the subsequent amine addition to furnish 15 (Scheme 5) illustrates another example of the reversibility of addition-elimination reactions [37],... 

The oxetane tertiary amides 15 on treatment with methyl triflate in anhydrous nitrobenzene at 150 °C undergo ring expansion to the cyclic acetals 16 and, if the groups R and R2 are sufficiently bulky, the acetals undergo a ring contraction to form the azetidines 17 . 

The intramolecular [2+3] cycloaddition of in situ generated azides to iV-methylnitrilium ions has also been used for the preparation of tetrazolium salts. With exclusion of moisture, treatment of 4-azidobutanenitrile 64 with methyl triflate in boiling 1,2-dichloroethane affords 1-methyl-6,7-dihydro-57/-pyrrolo[l,2-< ]tetrazolium trifluoromethane sulfonate 65 in 68% yield (Scheme 6) <1997MI671>. 

An intramolecular acetal has also been introduced by the treatment of a mixture of a 1-thio-mannoside, having a methoxybenzyl protecting group at C-2 and an alcohol with DDQ [71] (Scheme 4.4c). Activation of the thioglycoside with methyl triflate gave a P-mannoside as the only anomer. This approach was employed for the synthesis of the core pentasaccharide of N-linked glycoproteins. 

Although the coupling of glycosyl dithiophosphates using an excess methyl triflate as an activator in the presence of 2,6-di-tertbutylpyridine proceeded in a satisfactory yield (70%), the application of dimethylsulfonium triflate resulted in the formation of disaccharides in a considerably more effective way (94% yield). 

Mootoo and co-workers disclosed a procedure for the preparation of C-l substituted galactals based on the intramolecular capture of an oxocarbenium ion by an enol ether residue.79 In their approach, the key intermediate 1 -thio-1,2-O-isopropylidene acetals (TIA) are activated with methyl triflate to generate the crucial annulating synthon (1,2-O-isopropylidenated oxocarbenium ion). 

The polymer bound thioethyl 2-amido glucosyl 51a is a competent 2-amidoglucosyl donor toward glycal acceptors when activated with methyl triflate in the standard manner.21 The formation of P-2-aminoglucosyl C1 —>4 53) and p-2-aminoglucosyl (1—>3 54)-linked disaccharides proceeded in over 70% yield (Scheme 2.16). The P-2-aminoglucosyl (1 —>6)-linked disaccharide 52 was formed in lower yields. 

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