Ferf-Butyldimethylsilyl

Reagents Af-methyl-./V-(ferf-butyldimethylsilyl), trifluoroaceta-mide, MTBSTFA Add 0.25 ml of A,A-dimethylformamide (DMF) to the dried hydrolyzate. Add 0.25 ml of MTBSTFA reagent and cap tightly. Heat at 60° for 60 min, or overnight at room temperature (longer reaction times prevent mixtures of derivatives). Sample will need to be concentrated prior to injection. For trace analyses, it is important to use the minimum amount of solvent. 

PyBroP bromo(tripyrrolidino)phosphonium hexafluorophosphate TBS TBDMS, ferf-butyldimethylsilyl... 

The 0-silylation reaction of alcohols is important as a protection method of hydroxyl groups. 0-Silylations of liquid or crystalline alcohols with liquid or crystalline silyl chlorides were found to be possible in the solid state. For example, when a mixture of powdered L-menthol (26), ferf-butyldimethylsilyl chloride (27), and imidazole (28) was kept at 60 °C for 5 h, 0-tert-butyldi-methylsilyl L-menthol (29) was obtained in 97% yield [8] (Scheme 4). Similar treatments of 26 with the liquid silyl chlorides, trimethyl- (30a) and triethylsilyl chloride (30b), gave the corresponding 0-silylation products 31a (89%) and 31b (89%), respectively, in the yields indicated [8] (Scheme 4). However, 0-silylation of triisopropyl- (30c) and triphenylsilyl chloride (30d) proceeded with difficultly even at 120 °C and gave 31c (57%) and 31d (70%), respectively, in relatively low yields. Nevertheless, when the solvent-free silylation reactions at 120 °C were carried out using two equivalents of 30c and 30d, 31c (77%) and 31d (99%) were obtained, respectively, in relatively high yields. 

Figure 9 2, 5 -Bis-0-(ferf-butyldimethylsilyl)-3 -spiro-5"-(4"-amino-1",2"-oxa-thiole-2",2"-dioxide)pyrimidine (TSAO) derivatives TSAO-T, TSAO-m3T, and TSAO-e3T.

Trialkylsilyl-protected oligo(ethylene glycol)methacrylates, 2- 2- (tert-butyldimethylsilyl)oxy]ethoxy ethyl methacrylate (1), and 2- 2-[2-[(ferf-butyldimethylsilyl)oxy] ethoxy] ethoxy ethyl methacrylate (2) (Scheme 7) were used for the synthesis of amphiphilic block copolymers by anionic poly-... 

G. D. Kishore Kumar and S. Baskaran, A facile, catalytic, and environmentally benign method for selective deprotection of ferf-butyldimethylsilyl ether mediated by phosphomolybdic acid supported on silica gel, /. Org. Chem., 70 (2005) 4520-4523. 

Addition of allylic zinc bromides to nitrones, generated in situ from allylbro-mides and zinc powder in THF (670), allyltributylstannane (671) and lithiated allyl ferf-butyldimethylsilyl ether (672), proceeds regioselectively in good yields and is used to synthesize homoallyl hydroxylamines (Scheme 2.189). The latter were subjected to an iodo cyclization reaction (see Scheme 2.186). 

Deprotection of the spiroketal protected porphyrazines to generate the pz-diols proved difficult because the desired product is easily oxidized before isolation or derivitization. It was therefore anticipated that the high electron density of the de-protected pz-diol would be reduced by core-metalation, so attempts were made to deprotect ketal 193 with TFA to give enediol 201. However, 201 rapidly decomposed during purification attempts. To avoid this problem pz (201) was trapped with terl-bu(yIdiinc(liyIsi IyI triflate to give the ferf-butyldimethylsilyl derivative 202 (79%) as a stable compound (Scheme 40) (10). 

Reactions of various l-(l,2-propadienyl)cyclopropanols having a substituent at the 1- or 3-position of the propadienyl moiety 55 proceed smoothly at between 0°C and room temperature with 1.1 mole amounts of Co2(CO)8 in either THF or ethyl acetate, and various 2-monosubstituted or 2,3-disubstituted 1,4-hydro-quinone derivatives 58 are obtained in good yields (Scheme 25). In particular, 1-(1,2-propadienyI)cycIopropanoI having the ferf-butyldimethylsilyl group at the 1-position of the 1,2-prop adienyl moiety gives a high yield of the silylated hydroquinone. 

The unusual system franx-RulOl lTMPl/N OllO atm)/fluorobenzene epoxidised linear alkenes, cholesteryl acetate and the ferf-butyldimethylsilyl ether of citronellol [592] cholest-5-ene-3-one was oxidised to the 6a and 6p alcohols and the enedione by franx-RulOl lTMPl/OXCgH (Table 3.2) [593]. With ter-penes the 6,7-double bonds were selectively epoxidised by fran -Ru(0)2(TMP)/... 

DIAC heptakis(2,3-di-0-acetyl), TBDMS ferf-butyldimethylsilyl, DIME heptakis(2,3-di-0-methyl)... 

Scheme 21). Scheme 22 illustrates an example of kinetic resolution of a racemic allylic alcohol with a 1,3-hydrogen shift. When racemic 4-hydroxy-2-cyclopentenone is exposed to a cationic (/ )-BINAP-Rh complex in THF, the S enantiomer is consumed five times faster than the R isomer (32). The slow-reacting stereoisomer purified as the crystalline ferf-butyldimethylsilyl ether is an intermediate in prostaglandin synthesis (33). These isomerizations may occur via initial Rh-olefinic bond interaction (34). 

In asymmetric syntheses, the bulky (i-Pr)3Si group can direct 1,2-addition of phosphite 92 to (S j-triisopropylsilyloxy lactaldehyde (93) to afford adduct 94 preferentially along with the by-product 95 (equation 42)157. The stereochemical outcome results from the bulk of the (i-Pr)3Si protecting group9. Furthermore, the steric congestion in allylic cyanohydrin trimethylsilyl and ferf-butyldimethylsilyl ethers influences their regioselective 1,2- and 1,4-additions to carbonyl compounds under basic conditions158. 

The same technique was used950 to generate the l -(ferf-butyldimethylsilyl)bicy-clobutonium ion 529, which undergoes fast 1,3-hydride shift upon increasing temperature to yield 3-e static structure, which is due to the efficient stabilization by the y-ewiio-trialkylsilyl substituent. 

Selective deprotection of trialkylsilyl ethers can also be accomplished by Nafion-H. Trimethylsilyl ethers are cleaved to the corresponding alcohols under mild conditions680 [Eq. (5.241)]. Nafion-H with Nal (1 equiv.) in methanol was shown to readily cleave ferf-butyldimethylsilyl ethers (room temperature, 4—25 h,... 

Substituents can be introduced even at the lateral 4-position (1993JCS(P1)625). In the example shown in Scheme 122, the reactive 5-position is first protected by silylation effected by abstraction of the proton at C5 using a strong non-nucleophilic base like LiTMP, followed by treatment with TMS chloride. With the 5-position thus protected subsequent O-silylation of 431 to give 432 activates the lateral proton at the 4-position, which is removed by a second equivalent of base. The lateral anion 433 is then quenched with an electrophile like ferf-butyldimethylsilyl (TBDMS) triflate that produces 434. The entire sequence 430 -> 434 can be preformed in one pot. 

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