Ether, bis 2 benzyl

Figure 2. Acidolysis of a bis-benzylic ether model compound...

The cleavage of a terminal )3-phenylsulfonyl silyl group to give a methylenecyclopropane is readily accomplished by treatment with tetrabutylammonium fluoride (TBAF) in tetrahydro-furan. Thus, the bis(benzyl) ether of trani-3-methylenecyclopropane-l,2-dimethanol, trans-, 2-bis[(benzyloxy)methyl]-3-methylenecyclopropane (2), was obtained in 91% yield as part of a synthesis of oxetanocin. ... 

The most recent formal synthesis of (—)-swainsonine (378) to invoke the C-l/C-2 bond-forming approach, byjung and coworkers, used D-erythro-nolactone protected as the bis(benzyl) ether 431 as the chiral educt (Scheme 60). " Although reduction with diisobutylaluminum hydride and Wittig reaction of the resulting lactol with benzylidenetriphenylphosphorane gave a mixture of cis- and fra s-alkenes, isomerization with thiophenol and AIBN produced the fraws-alkene (+)-432 exclusively. Swem oxidation... 

Cm.OROCARBONSANDCm.OROHYDROCARBONS - BENZYL Cm ORIDE, BENZAL Cm ORIDE AND BENZOTEICm.ORIDE] (Vol 6) Bis(chloromethyl) ether [542-88-1]... 

An 80% yield of benzyl chloride is obtained with sulfuryl chloride as chlorinating agent. Yields of >70% of benzyl chloride are obtained by the zinc chloride-catalyzed chloromethylation of benzene but formation of bis-chloromethyl ether presents a health hazard for this reaction pathway. 

A powerful solvent effect is observed in the reaction of /j-nitrobenzaldehyde with sulfur telrafluonde The reaction conducted in a benzene solution gives the expected p nitrobenzyhdene fluoride, without a solvent, bis(p-nitro a fluoro-benzyl) ether is formed as the sole product [171 (equation 86)... 

Merck s thienamycin synthesis commences with mono (V-silylation of dibenzyl aspartate (13, Scheme 2), the bis(benzyl) ester of aspartic acid (12). Thus, treatment of a cooled (0°C) solution of 13 in ether with trimethylsilyl chloride and triethylamine, followed by filtration to remove the triethylamine hydrochloride by-product, provides 11. When 11 is exposed to the action of one equivalent of tm-butylmagnesium chloride, the active hydrogen attached to nitrogen is removed, and the resultant anion spontaneously condenses with the electrophilic ester carbonyl four atoms away. After hydrolysis of the reaction mixture with 2 n HC1 saturated with ammonium chloride, enantiomerically pure azetidinone ester 10 is formed in 65-70% yield from 13. Although it is conceivable that... 

With ring G in place, the construction of key intermediate 105 requires only a few functional group manipulations. To this end, benzylation of the free secondary hydroxyl group in 136, followed sequentially by hydroboration/oxidation and benzylation reactions, affords compound 137 in 75% overall yield. Acid-induced solvolysis of the benzylidene acetal in 137 in methanol furnishes a diol (138) the hydroxy groups of which can be easily differentiated. Although the action of 2.5 equivalents of tert-butyldimethylsilyl chloride on compound 138 produces a bis(silyl ether), it was found that the primary TBS ether can be cleaved selectively on treatment with a catalytic amount of CSA in MeOH at 0 °C. Finally, oxidation of the resulting primary alcohol using the Swem procedure furnishes key intermediate 105 (81 % yield from 138). 

Arguably the most challenging aspect for the preparation of 1 was construction of the unsymmetrically substituted sec-sec chiral bis(trifluoromethyl)benzylic ether functionality with careful control of the relative and absolute stereochemistry [21], The original chemistry route to ether intermediate 18 involved an unselective etherification of chiral alcohol 10 with racemic imidate 17 and separation of a nearly 1 1 mixture of diastereomers, as shown in Scheme 7.3. Carbon-oxygen single bond forming reactions leading directly to chiral acyclic sec-sec ethers are particularly rare since known reactions are typically nonstereospecific. While notable exceptions have surfaced [22], each method provides ethers with particular substitution patterns which are not broadly applicable. 

BAm = benzylamine BE = benzyl ether BMI.Tf2N = bis(trifluoromethane)sulfonamide of l-n-butyl-3-methylimidazolium CH = cyclohexane ... 

Bisacid 91 was used toward three different targets. For the first, a palladium-catalyzed decarboxylative Heck reaction followed by perylenequinone formation provided bis-styryl derivative 92 (Scheme 7.22) [52]. For the second, the C5,C5 -benzyl ethers were cleaved, and the more acidic carboxylic acids were then selectively benzylated using BnBr and K2CO3 (Scheme 7.22). This re-esterification... 

Hydroxythiadiazole and neat trimethyl orthoacetate showed a 20 80 ratio of N- versus O-alkylation products by H NMR <2002EJ01763>. The acidic hydroxyl group of thiadiazole 130 can be selectively protected as the benzyl ether 113 (Equation 22) <2004TL5441>. Nonhydrogenative debenzylation of the bisbenzyl thiadiazole 116 was achieved with boron tribromide to afford the bis-l,2,5-thiadiazole 131 (Equation 23) <2004TL5441>. 

Thermolytic Cleavage of Allvlic and Benzvlic Ethers and Polvethers. The thermal lability of the types of ethers which are of interest in the context of this study was discovered during a thorough study of the application of certain benzylic carbonates as labile protecting groups for alcohols and phenols [IS]. It was observed that, under acid catalysis, the bis-methylcarbonate derivative of l-(4-hydroxyphenyl)ethanol (4, in Equation 1) was transformed into the benzylic ether (5) which then underwent clean acid-catalyzed thermolysis to the corresponding styrene (6) in very high yield [14]. 

AUylic ethers were reduced by treatment with lithium in ethylamine to alkenes [636]. Benzyl ethers are hydrogenolyzed easily, even more readily than benzyl alcohols [637], 3,5-Bis(benzyloxy)benzyl alcohol gave 3,5-dihydroxy-benzyl alcohol on hydrogenation over palladium on carbon at room temperature and atmospheric pressure in quantitative yield [638. Hydrogenolysis of benzylic ethers can also be achieved by refluxing the ether with cyclohexene (as a source of hydrogen) in the presence of 10% palladium on carbon in the presence of aluminum chloride [639]. 

Chiral bis(oxazoline) 27 is an effective chiral coordinating agent for enantiocontrol in the [2,3]-Wittig rearrangement. The rearrangement of (Z)-crotyl benzyl ether 84 with f-BuLi/(5, 5)-27 (1.5 equivalents each) in hexane provided [2,3]-shift product (l/ ,25 )-85 in 40% ee (equation 46The feasibility of the asymmetric catalytic version was also examined. In this case, the rearrangement with 20 mol% of 27 in ether was found to provide the same level of enantioselectivity (34% ee). 

As shown in equation 55, when the benzyl ether of ci.s-2-butcn-1,4-diol is treated with bis(iodozincio)iodomethane, the cyclopropylzinc intermediate is obtained and reacts with various electrophiles. The obtained cyclopropyl derivative has all-d.v configuration. In this reaction, zinc halide, which is present in the solution, plays an important role79. 

Figure 14.6 Resonance stabilization of reactive intermediates from (i) bis(chloromethyl) ether, (ii) aliphatic nitrogen mustard, (iii) allyl chloride, (iv) benzyl chloride, (v) bis(morpholino)methane, (vi) benzoyl chloride, and (vii) dimethylcarbamyl chloride.

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

Cyclization of allylic alcohols to form epoxides has been particularly problematical, and the reactions have been more of mechanistic than of synthetic interest. For reactions conducted under basic conditions, it is possible that epoxide formation involves initial halogen addition followed by nucleophilic displacement to form the epoxide. Early examples of direct formation of epoxides from allylic alcohols with sodium hypobromite," bromine and 1.5 M NaOH,12 and r-butyl hypochlorite13 have been reviewed previously.fr Recently it has been shown that allylic alcohols can be cyclized effectively with bis(jym-collidine)iodine(I) perchlorate (equation 3).14 An unusual example of epoxide formation competing with other cyclization types is shown in equation (4).15 In this case, an allylic benzyl ether competes effectively with a -/-hydroxyl group as the nucleophile. 

Cyclization of the bis-epoxides 123 (mixtures of diastereomers) with benzylamine afforded the azepanes 124 in a preferential 1-endo-tet methodology (Equation 17) <1995JOC5958> however, with the corresponding 3,4-benzyl ethers of the bis-epoxides rather than the // / -acetonide protecting group, no cyclization to six-membered ting species was observed. The azepanes 124 were then converted in two steps to the amino sugar hydrochloride salts 126 via the N-debenzylated intermediates 125 (Scheme 16). 

Deprotection of allyl aryl ethers is accomplished by protonolysis with palladium on activated charcoal in methanol solution in the presence of toluene-p-sulphonic acid,42 or by reduction with sodium bis(2-methoxy-ethoxy)aluminium hydride in toluene solution43 (Aldrich). This latter reagent also cleaves aryl benzyl ethers. 

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