Triphenylmethyl methyl ether

Triphenylmethyl methyl ether Trityl methyl ether... 

FIG. 1 H nmr spectrum of triphenylmethyl methyl ether (trityl methyl ether) (250 MHz). 

Benzyl and triphenylmethyl ethers of carbohydrates are preferred over methyl ethers when selective removal of protecting groups is important. The relatively high nucleophilic activity of the 5-hydroxyl group in glycosides and 1,2-O-alkylidene derivatives of 4 permits its benzylation and triphenylmethylation under mild conditions. Thus, treatment of 33 (Ref. 34) and 36 (Ref. 57) with benzyl bromide and... 

Photoheterolytic cleavage of benzyl alcohol in neutral media occurs only when it gives rise to highly stabilized cations, such as triphenylmethyl cations (compare Sec. 15.1 the reaction may be at least in part adiabatic in this case and yield the excited cation) [79-81], xanthyl [82] or fluorenyl cations [83]. However, acid catalysis is effective and methyl ethers are by far the main products from benzyl alcohols in acidified aqueous methanol [84-88]. Electron donating substituents in the ortho and, to a lesser extent, in the meta position enhance the quantum yield (acid catalysis may be... 

The fluoroborate of 11 could be prepared from the perchlorate or directly from the cyclopropene 10. This ion was used to synthesize tri-n-propylcyclopropene (12), either by direct reaction with n-propyllithium or by conversion of the cation to di-n-propylcyclopropenyl methyl ether (13) and reaction of this compound with n-propylmagnesium bromide. The cyclopropene was converted directly to the ion 14 with triphenylmethyl perchlorate (equation 6). 

The facts that triphenylmethyl chloride (pKR = —6.6) forms a covalent solid and that all known carbinols and methyl ethers are covalent indicate that the calculations are at least reasonable. Interestingly, the fluorides of most cations are predicted to form covalent solids. I do not know of data to support or contradict this prediction. Also, possibly an acetate can be found... 

Iron pentacarbonyl and l-methoxy-l,4-cyclohexadiene react as shown by Birch and oo-workera, but in dibutyl ether this solvent has been found superior. The tricarbonyl(methoxy-l,3-cyclohexadiene)iron isomers undergo hydride abstraction with triphenylmethyl tetrafluoro-borate to form the dienyl salt mixture of which the 1-methoxy isomer is hydrolyzed by water to the cyclohexadienone complex. The 2-methoxy isomer can be recovered by precipitation as the hexafluoro-phosphate salt. By this method the 3-methyl-substituted dienone complex has also been prepared from l-methoxy-3-methylbenzene. The use of the conjugated 1-methoxy-1,3-cyclohexadiene in Part B led to no increase in yield or rate and resulted chiefly in another product of higher molecular weight. An alternative procedure for the dienone is to react tricarbonyl(l,4-dimethoxycyclohexadiene)iron with sulfuric acid. ... 

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

In carbohydrate chemistry, the preparation of ethers that are stable in the presence of acids, bases, and aqueous alkali is an important analytical and synthetic tool. The methods used for the etherification of hydroxyl groups51 generally employ reactions of unprotected sugars and glycosides with methyl, allyl, benzyl, triphenylmethyl, and alkylsilyl halides in the presence of a variety of aqueous and nonaqueous bases. 

To a stirred solution of the (lS,2S,3S)-2-(2,2-dibromovinyl)-3-methyl-l-triphenylmethoxymethyl-cyclopropane (128.6 mg, 0.251 mmol) in THF (5 ml) was added dropwise a 1.42 M solution of nBuLi (0.35 ml, 0.50 mmol) in hexane at -78°C. After stirring at -78°C for 10 min, the solution was poured into H20 (30 ml) and extracted with Et20 (3x30 ml). The organic extracts were combined, washed with brine, dried over sodium sulfate and filtered. The solvent was removed in vacuum to give a colorless residue, which was purified by column chromatography over silica gel (hexane-Et20, 20 1) to afford 81.4 mg (92%) of (lS,2S,3S)-3-ethynyl-2-methylcyclopropylmethyl triphenylmethyl ether as a colorless viscous oil. 

A mixture of chlorotrimethylsilane (0.205 mmol) was added to a suspension of n. v-3-aminocyclohexanecarboxylic acid (0.205 mmol) suspended in 500 ml CH2Cl2/acetonitrile, 5 1, and refluxed for 2 hours. Once cooled, triethylamine (0.410 mmol) was added dropwise to the mixture followed immediately by the portionwise addition of triphenylmethyl chloride (0.205 mmol). The mixture was stirred 18 hours and sufficient methyl alcohol was added to dissolve the vessel contents. The solution was concentrated and the residue was partitioned between 800 ml diethyl ether/10% citric acid, 1 1. The ether layer was collected and combined with a 150 ml diethyl ether extraction from the citric acid layer. Combined fractions were extracted three times with 250 ml 2 M NaOH and once with 100 ml water. These layers were washed twice with 150 ml diethyl ether, cooled to 0°C, acidified to pH 7 with 12 M HC1, and re-extracted three times with 200 ml EtOAc. The extract was dried over MgS04, then concentrated, and the product isolated in 85% yield as a white foam. 

Triphenylmethyl ethers of sugars are important, as well as the methyl,782 ethyl, and benzyl ethers.783 For a comprehensive collection of references see Stanek et aJ.1SAr... 

R. C. Hockett and D. F. Mowery Jr., Lead tetraacetate oxidations in the sugar group. III. Triphenylmethyl ethers of P-methyl D-arabinopyranoside and a-methyl L-fucopyranoside. The determination of their structures, J. Am. Chem. Soc., 65 (1943) 403-409. 

Methyl 2,3-di-0-methyl-6-0-triphenylmethyl-a-27 and p-o-xy/o-hexopyranosid-4-uloses 22 have been used as model substrates for these smdies (Fig. 1.4). The reaction of glucopyranosid-4-ulose 21 with an ethereal solution of methyllithium (LiBr-firee) at —80 °C afforded methyl 2, 3-di-(9-methyl-6-(9-triphenylmethyl-a-D-glucopyranoside 23 as the only product in which the C4 methyl group is axially oriented. 

Reaction of the same oxo sugar 21 with an ethereal solution of methylmagnesium iodide at —80 °C proceeded again with high stereoselectivity, but the obtained product 24 was now the C4 epimer of the branched-chain sugar 23, namely, methyl 2, 3-di-G-methyl-6-C)-triphenylmethyl-a-D-galactopyranoside 24. 

The high stereoselectivity of the addition of methyllithium to the C4 carbonyl group was lost when an ethereal solution of methyllithium reacted with the p-anomer of 27, at 80 °C, namely, with the methyl 2, 3-di-0-methyl-6-0-triphenylmethyl-P-D-xy/o-hexopyranosid-4-ulose 22, whereby a mixture of C4 epimers 25 and 26 was obtained... 

The adoption of any conformation other than " Ci by 21 prior to the addition of methylhthium to the C4 carbonyl carbon should result in the axial addition of methyllithium, since the severe electrostatic and nonbonding steric interaction between the electronegative anomeric (Cl) methoxy group and the equatorially approaching methyl carbanion of methyllithium will impede the equatorial addition of methyllithium. In the case of an axial attack of methyllithium to the C4 carbonyl carbon, these severe 1,4-diaxial electrostatic and steric interactions are avoided. This rationalization is strongly supported by the finding that methyl 2, 3-di-O-methyl-6-0-triphenylmethyl-p-D-xy/o-hexopyranosid-4-ulose 22, where such 1, 4-diaxial electrostatic and nonbonded steric interactions do not exist, reacts with an ethereal solution of methyllithium at —80 °C to yield both C4 epimers (25 and 24, Fig. 1.4). 

Di-O-methyl-D-glucose and thence the corresponding dimethyl-D-fruc-tose was produced from l,2-0-isopropylidene-6-0-triphenylmethyl-a-D-glucofuranose and purified by way of its a-1,2,6-triacetate, catalytic treatment of which, with sodium methoxide, gave the 6-acetate. Reaction with a stronger solution of this reagent afforded the fructose dimethyl ether. 1,6-Anhydro-... 

Azobisisobutyronitrile Cyclohexyl Methanesulfonyl Methanesulfonyl chloride Methyl fcrf-butyl ether t-Butyldiphenylsilyl t-Butyldiphenylsilyl chloride Trityl (triphenylmethyl) Tosyl... 

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