Benzyl trifluoromethanesulfonate

Benzyl trifluoromethanesulfonate has been shown to be a powerful benzylating agent (for review, see Ref. [98]). Benzylations with the in situ prepared reagent in the presence of 2,4,6-trimethylpyridine or similar bases proceed readily at —60 °C, wherein neither an acetyl group migration nor a loss of acetyl groups occurs [99, 100] (see also, Ref. [29]). 

Benzyl trifluoromethanesulfonate. Preparation of tri-O-acetyl-2-O-benzyl-a-D-galactopyranosyl bromide from 1,3,4,6-tetra-O-acetyl-a-D-galactopyranose, R. U. Lemieux and T. Kondo, Carbohydr. Res., 35 (1974) C4-C6. 

Related Reagents. Benzyl Chloride Benzyl Iodide Benzyl p-Toluenesulfonate Benzyl 2,2,2-Triehloroacetimidate Benzyl Trifluoromethanesulfonate 3,4-Dimethoxybenzyl Bromide p-Methoxybenzyl Chloride 4-Methoxybenzyl 2,2,2-Triehloroacetimidate. 

Related Reagents. Benzyl Bromide Benzyl Chloride Benzyl Iodide Benzyl Trifluoromethanesulfonate 3,4-Dimethoxybenzyl... 

Related Reagents. Benzyl Chloride Benzyl 2,2,2-Trichloroacetimidate Benzyl Trifluoromethanesulfonate p-methoxy benzyl bromide p-methoxy 2,2,2-trichloroacetimidate. 

Thus, the best compromises for Boc and Fmoc chemistries seem to be cyclohexyl and 2,4-dimethylpent-3-yl (Dmpn), which is of intermediate stability, and the removal of which by trifluoromethanesulfonic acid with the aid of thioanisole (see Section 6.22) leads to minimal imide formation (see Section 6.13). Points to note are that acidolysis of esters by hydrogen fluoride can lead to fission at the oxy-car-bonyl bond instead of the alkyl-oxy bond, thus generating acylium ions that can react with nucleophiles (see Sections 6.16 and 6.22), and that benzyl esters may undergo transesterification if left in methanol. The side reactions of cyclization (see Section 6.16) and acylation of anisole (see Section 6.22) caused by acylium ion formation do not occur at the side chain of aspartic acid.47-51... 

It may be suspected that the genuinely topotactic (as secured by the molecular precision of the AFM [18]) photodimerization of 2-benzyl-5-benzyli-denecyclopentanone [118] might be a good candidate for a quantitative preparative photo dimerization to give the head-to-tail anti-[2+2] dimer. Early quantitative solid-state [2-1-2] photodimerizations (most of the published mechanistic interpretations of which can no longer be accepted) are listed in [110]. These deal with the anti dimerization of acenaphthylene-1,2-dicarboxylic anhydride, the head-to-head syn dimerization of acenaphthylene-1-carboxylic acid, the syn dimerization of 5,6-dichloroacenaphthylene, and the thermally reversible head-to-tail anti dimerization of seven ( )-2,6-di-f-butyl-4-(2-aryl-ethenyl)pyrylium-trifluoromethanesulfonates. All of these reactions proceed fully specific. On the other hand, quantitative photoconversions of a 1 1 mixed crystal of ethyl and propyl a-cyano-4-[2-(4-pyridyl)ethenyl]cinnamates gives mixtures of diesters with one (A>410 nm) or two cyclobutane rings (no cutoff filter). 

DIKETONES l-Benzyl-4-(2-hydioxy-ethyl)-5-methyl-l, 3-thiazolium chloride. Copper(II) trifluoromethanesulfonate. 

Several new effective Friedel-Crafts catalysts have been developed. These include triflate93 (trifluoromethanesulfonate) derivatives of boron, aluminum, and gallium [M(0S02CF3)3]. Trichlorolanthanides have also been proved to be active reusable catalysts in benzylation.94 Superacids as catalysts are also very efficient in many Friedel-Crafts alkylations.95... 

Ytterbium trifluoromethanesulfonate promoted a radical atom-transfer addition of chiral 3-bromoacetyl-2-oxazolidinones to norbornadiene, which afforded the corresponding 5-ex<9-3-bromo-5-nortricycleneacetic acid derivatives in good yields and with high diastereoselectivity (90-96% de, when using the chiral 4-isopropyl- and 4-benzyl-substituted 2-oxazolidinone auxiliaries).133... 

Oxidation. This reagent is prepared by reaction of CAN with K2C03 (2 equiv.) to form Ce(C03)2, which is then treated with trifluoromethanesulfonic acid (4 equiv.). This oxidant is effective for oxidation of benzylic alcohols to aldehydes (72-92% yield), and of alkylarenes to aldehydes or ketones (65-70% yield). 

The seven-membered phostone 252 was synthesized by the reaction of methyl 2,3-di-0-benzyl-4,6-0-benzyl-idene-a((3)-D-glucopyranoside 251 with triethyl phosphate and trimethylsilyl trifluoromethanesulfonate. Protecting the acetal group of 251 interacted with triethyl phosphite and opened to give 252, which can be further selectively hydrolyzed or deprotected to give 253 or 254 <2003TL8797>. 

Facile synthesis of simple 3-arylpyrroles from pyrroline by tandem Suzuki dehydrogenation reaction is depicted in Scheme 229. Thus, treatment of l-benzyl-2,5-dihydro-l//-pyrrol-3-yl trifluoromethanesulfonate 1195 (prepared in 55% yield from l-benzyl-3-pyrrolidinone 1194 by trapping the enolate with a triflating reagent), with boronic acid derivatives leads to the formation of 3-arylpyrroles 1196 in good yields (65-74%) <2000TL3423>. 

TFA at higher temperatures,or TFA/thioanisole where the push-pull mechanism remarkably increases the rate of acidolysis,f l liquid HF/pyridine,t °l BBrj/CHaQa, or BBrj/TFA for longer peptide fragments.By these procedures also the benzyl-type side-chain protection is cleaved as well as Arg(Tos). Additionally, numerous sulfonic acids were shown to efficiently remove the Z group, such as methanesulfonic acid, trifluoromethanesulfonic acid, or fluorosulfonic acid mainly in CH2CI2 or Since the acidolytic removal of the... 

Abbreviations Ac acetyl AIBN azobisisobutyronitrile All allyl Bn benzyl Bz benzoyl ClAc chloroacetyl DAST diethylaminosulfur trifluoride DBU l,8-diazabicyclo[5.4.0]-undec-7-ene DDQ 2,3-dichloro-5,6-dicyano-/)-benzoquinone DMDO dimethyldioxirane DMTST dimethyl(methylthio)sulfonium trifluoromethanesulfonate Fmoc 9-fluorenyl-methoxycarbonyl HDTC hydrazine dithiocarboxylate IDCP iodonium di-collidine perchlorate Lev levulinoyl MBz 4-methylbenzoyl Me methyl MEK methyl ethyl ketone MP 4-methoxyphenyl NBS iV-bromosuccinimide NIS A-iodosuccinimide Pent n-pentenyl Pfp pentafluorophenyl Ph phenyl Phth phthaloyl Piv pivaloyl PMB 4-methoxybenzyl TBAF tetrabutylammonium fluoride TBDMS tcrt-butyldimethylsilyl TBDPS tert-butyldiphenylsilyl TCA trichloroacetyl TES triethylsilyl Tf trifluoromethanesulfonyl TMS trimethylsilyl Tol 4-methylphenyl Tr trityl Troc 2,2,2-trichloroethoxycarbonyl Ts tosyl. 

To a solution of silver trifluoromethanesulfonate (7.71 g, 30 mmol) in dry dichloromethane (100 mL) at —40°C in the dark is added dropwise a solution of 9-fluorenylmethoxycarbony 1 serine benzyl ester 11 (8.45 g, 20 nunol), 2,3,4-tri-O-benzoyl-a-D-xylopyranosyl bromide 12 (11.14 g, 21.2 nunol) and tetramethyl urea (3.65 g, 31.4 nunol) in dichloromethane (100 mL). After 18 h of stirring at room temperature, the precipitate is filtered off and washed with dichloromethane (200 mL). The organic solution is washed with water (200 mL), 1% KHCO3 solution (twice 200 mL) and water, dried with Na SO, and concentrated in vacuo. The crude product is recrystallized from ethyl acetate-n-hexane. (If the reaction was not complete, chromatography on silica gel 60 in toluene/ethanol 9 1 is recommended). Yield 15 g (87%) mp 136°C, [a], —27.8° (c 1.3, CHCI3), 0.64 (toluene/ethanol 26 1). 

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