Trityl trifluoroacetate

DEHYDROGENATION t-Butyl hypochlorite. 2,3-Dichloro-5,6-dicyanobenzoquinone. Pyridine. Pyridinium hydrobromide. Sodium bis-(2-methoxyethoxy)aluminum hydride. Sulfur. Trityl tetrafluoroborate. Trityl trifluoroacetate. 

CF3COOH, TFAA, CH2CI2. These conditions afford the trifluoroacetate, thus preventing retritylation, which is sometimes a problem when a trityl group is cleaved with acid. A further advantage of these conditions was that a SEM group was completely stable. When TFAA was not used. 

Acid-catalyzed dealkoxylation is particularly suitable for the preparation of highly reactive, cationic iron(IV) carbene complexes, which can be used for the cyclopropanation of alkenes [438] (Figure 3.11). Several reagents can be used to catalyze alkoxide abstraction these include tetrafluoroboric acid [457-459], trifluoroacetic acid [443,460], gaseous hydrogen chloride [452,461], trityl salts [434], or trimethylsilyl triflate [24,104,434,441,442,460], In the case of oxidizing acids (e.g. trityl salts) hydride abstraction can compete efficiently with alkoxide abstraction and lead to the formation of alkoxycarbene complexes [178,462] (see Section 2.1.7). 

NMO NMP Nu PPA PCC PDC phen Phth PPE PPTS Red-Al SEM Sia2BH TAS TBAF TBDMS TBDMS-C1 TBHP TCE TCNE TES Tf TFA TFAA THF THP TIPBS-C1 TIPS-C1 TMEDA TMS TMS-C1 TMS-CN Tol TosMIC TPP Tr Ts TTFA TTN N-methylmorpholine N-oxide jV-methyl-2-pyrrolidone nucleophile polyphosphoric acid pyridinium chlorochromate pyridinium dichromate 1,10-phenanthroline phthaloyl polyphosphate ester pyridinium p-toluenesulfonate sodium bis(methoxyethoxy)aluminum dihydride (3-trimethylsilylethoxy methyl disiamylborane tris(diethylamino)sulfonium tetra-n-butylammonium fluoride f-butyldimethylsilyl f-butyldimethylsilyl chloride f-butyl hydroperoxide 2,2,2-trichloroethanol tetracyanoethylene triethylsilyl triflyl (trifluoromethanesulfonyl) trifluoroacetic acid trifluoroacetic anhydride tetrahydrofuran tetrahydropyranyl 2,4,6-triisopropylbenzenesulfonyl chloride 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane tetramethylethylenediamine [ 1,2-bis(dimethylamino)ethane] trimethylsilyl trimethylsilyl chloride trimethylsilyl cyanide tolyl tosylmethyl isocyanide meso-tetraphenylporphyrin trityl (triphenylmethyl) tosyl (p-toluenesulfonyl) thallium trifluoroacetate thallium(III) nitrate... 

Abbreviations AllocOSu, allyloxycarbonyl-A-hydroxysuccinimide BCIP, 5-bromoA-chloro-3-indolyl Boc, tert-butyloxycarbonyl tBu, tert-butyl DCM, dichloromethane Dde, l-(4,4-dimethyl-2,6-dioxocyclohex-l-ylidene)ethyl Ddz, a, a-dimethyl-3,5-dimethoxyben-zyloxycarbonyl DIC, A,A -diisopropylcarbodiimide DIEA, A,fV-diisopropylethylamine DMF, iV,./V-dimethylformamide FmocOSu, 9-fluorenylmethyloxycarbonyl-AMiydroxysucci-nimide OBOC, one-bead one-compound PBS, phosphate-buffered saline Pmc, 2,2,5,7,8-pentamethylchroman-6-sulfonyl PTH, phenylthiohydantoin RR, relative reactivities Teoc, 2-(trimethylsilyl)ethoxycarbonyl TFA, trifluoroacetic acid Trt, trityl. 

The treatment of 27/-tellurachromene with an equimolar amount of trityl perchlorate in trifluoroacetic acid leads to tellurachromylium perchlorate 60 obtained in low yield (86KGS1570 88KGS1050) (see Section II,H,1). 

Trityl ethers are easily cleaved by mild pro tic acids such as aqueous acetic or trifluoroacetic acid owing to the stability of the triphenylmethyl carbocation. They are also labile in the presence of Lewis acids such as ZnBr2—MeOH, FeCl3 or BF3 Et20.2 Trityl ethers can be cleaved selectively in the presence of TBDMS ether and isopropylidene acetals by brief exposure to formic acid.22 Catalytic hydrogenation has also been used to effect (9-detritylation. 

The disilyl derivative of all-cix-1,2-epoxycyclopentane-3,5-diol 5 7 was treated with diethyloctynylalane to afford after cleavage of the silylether function the triol 58. This triol was convered via the acetonide to the benzyl ether 59. Hydrolysis with aqueous trifluoroacetic acid yielded the diol benzylether 60 which could be prepared by an alternative route as well. This route proceeds via the monotrityl epoxide 61 and benzylation to the trityl benzylether 62 and then reaction with diethyl octynyl alane to the diolbenzylether 60 and the isomeric 1,3-diol. 

Di-BOC-l,4,7-triazonanes are smoothly deprotected with trifluoroacetic acid (TFA) in dichloromethane <2001JA5030, 2001JA6025>. Triazonines can be selectively cleaved from the trityl-type polymer support with 1% TFA in CH2C12, while BOC-protecting groups are not affected under these conditions <2004SL453>. 

The S-trityl ether of cysteine has been prepared by reaction of the amino add with triphenylmethanol in acetic add in the presence of trifluoroborane etherate43 or with triphenylmethanol in neat trifluoroacetic add.44 Slightly lower mp and spedfic rotation were recorded for the product obtained by the more... 

E22b, Section 6.1.1.2.1)j l Por stepwise regioselective disulfide formation, the iodine-mediated oxidative deprotection of a pair of Cys(Trt) residues is a widely applied procedure (see Vol.E22b, Sections 6.1.2-6.1.4). Finally, 5-trityl groups are efficiently cleaved with metal ions such as mercury(II) and silver(I),t 51 or with thalhum(III) trifluoroacetate.P ... 

Carbonyl compounds are reduced to symmetrical ethers, probably by way of reduction of some of the starting material to a silyl ether (9), reaction to form the mixed ketal (10) and then reductive replacement of the silyloxy group. Some hydrocarbon may be obtained as a by-product by reduction of (9 Scheme 4). Among the acid partners that have been used are trifluoroacetic acid, trityl perchlorate (with aldehydes) and electrogenerated protons. With Nafion resin symmetrical ethers are obtained from aldehydes, but silyl ethers are obtained from ketones. ... 

Also the trityl group was applied for the masking of SH functions. The sulfides were prepared by the reaction of the thiol with trityl chloride (75% yield) or from trityl alcohol and the thiol in the presence of anhydrous TFA (85-90% yield). The cleavage of this group can be carried out under several conditions (Scheme 58). It is sensitive to acids (e.g. trifluoroacetic acid/ethanethiol 1 1) and to heavy metals. Thiocyanogen (SCN)2 oxidizes 5-trityl ethers to the disulfides and iodine converts 5-tritylcy -teine derivatives to cystine structures. 

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