Silyl triflat

THP ethers can be converted directly to TBDMS and TES ethers using the silyl hydride and Sn(OTf)2 or the silyl triflate (70-95% yield). The use of TMSOTf gives the free alcohols upon isolation. ... 

These undergo silylation using the more reactive silyl triflate in the presence of 2,6-lutidine or triethylamine as base in dichloromethane. 

Silyl enol ethers, 23, 77, 99-117,128 Silyl enolates, 77 Silyl peroxides, 57 Silyl triflate, 94 Silyl vinyl lithium, 11 (E)-l -Silylalk-1 -enes, 8 Silylalumimum, 8 Silylation, 94 reductive, 26 a-C-Silylation, 113 O-Silylation.99,100 / -SilyIketone, 54 non-cydic, 55 Silylmagnesium, 8 Silyloxydienes, 112 Sodium hexamethyldisilazide, 89 Sodium thiosulphate pentahydrate, 59 Stannylation, see Hydrostannylation Stannylethene, 11 (Z)-Stilbene, 70 (E)-Stilbene oxide, 70 /3-Styryltrimethylsilane, 141 Swern oxidation. 84,88... 

A novel and versatile method for preparing polymer-supported reactive dienes was recently developed by Smith [26]. PS-DES (polystyrene diethyl-silane) resin 28 treated with trifluoromethanesulfonic acid was converted to a polymer-supported silyl triflate 29 and then functionalized with enolizable a,jS-unsaturated aldehydes and ketones to form silyloxydienes 30 and 31 (Scheme 4.4). These reactive dienes were then trapped with dienophiles and the Diels Alder adducts were electrophilically cleaved with a solution of TFA. 

A polymer-supported silyl triflate and subsequent functionalization synthesis and solid-phase Diels-Alder reactions of silyloxydienes [25]... 

The silyl ketene acetal rearrangement can also be carried out by reaction of the ester with a silyl triflate and tertiary amine, without formation of the ester enolate. Optimum results are obtained with bulky silyl triflates and amines, e.g., f-butyldimethylsilyl triflate and (V-methyl-Af, /V-dicyclohcxylaminc. Under these conditions the reaction is stereoselective for the Z-silyl ketene acetal and the stereochemistry of the allylic double bond determines the syn or anti configuration of the product.243... 

Nucleophilic addition of furan to nitrone occurs upon treatment with trimethyl-silyl triflate (TMSOTf) (586, 587). Catalyzed TMSOTf stereoselective addition of 2-[(trimethylsilyl)oxy]furan to chiral nitrones was carried out in a short synthesis of [IS (la, 2[), 7f>, 8a, 8aa)]-l,2-di(t-butyldiphenylsilyloxy)-indolizidine-7,8-diol (588). Addition to N -gulosyl-C-alkoxymethyl nitrones led to the synthesis of the core intermediate of polyoxin C (218). 

In other cases, the use of silyl triflates leads to double silylation of the starting AN. (This process will be considered separately in Section 3.5.1. Silylation of AN containing functional groups at the 3 -carbon atom will also be considered separately in Section 3.5.5.)... 

The reaction is performed at —94°C in dichloromethane and, generally, in the presence of catalytic amounts of silyl triflate. Although the reaction can be performed with trimethylsilyl derivatives as well, it is advantageous to use hydrolytically more stable SilV Bu derivatives. The reaction of 1,4-dinitrobutane can afford both mono- and bis-C,C-coupling products. 

A priori, derivatives of triflic acid (silyl triflates, salts of triflic acid, etc.) correspond to the above conditions. After a series of experiments, Zn(OTf)2 was chosen as the most efficient LA for the rearrangement BENA—>(504) (Scheme 3.261) (534). (It should be noted that the rearrangement BENA—>(504) under the action of silyl LA has been observed earlier (188, 465, 466), but the yields of derivatives (504) have been disappointing.)... 

Trialkylsilyl cations may play a key role in Lewis acid-catalyzed reactions. Trimethyl-silyl triflate itself is not a good catalyst, but in combination with other Lewis acids it generates excellent catalytic activity. 

Acetalizatioru Aldehydes and ketones are converted into acetals and ketals, respectively, by reaction with alkoxytrimethylsilanes in the presence of trimelhyl-silyl triflate as catalyst. 

The use of a silyl triflate and triethylamine to carry out the Ireland-Claiscn rearrangement was successfully employed by Nakai and co-workers60 in the early 1980s to convert allylic 3,3,3-trifluoropropionates 17 into 2-(trifluoromethyl)alk-4-enoic acids 18 (Table 22). The low dia-stereoselectivily in the rearrangement of 17b was attributed to the mixture of (E)- and (Z)-l-... 

A number of acyl trimethyl silanes chiral at the a- or -carbon atom have been prepared in non-racemic form. Chiral a-alkoxy and a-silyloxy acyl silanes have been generated in very high yields by oxidative rearrangement of enantiomerically pure silyl epoxides, induced by dimethyl sulphoxide and silyl triflates (Scheme 32)112. 

Two recently developed coupling reactions of an alkene (R1CH2CH=CH2), an aldehyde (R2CHO), and a silyl triflate (R33SiOTf) yield an allylic (66) or homoallylic (67) alcohol (in protected form).188 Employing nickel-phosphine catalysts, either product can be selected by small changes in the phosphine component. A mechanism distinct from that of Lewis acid-catalysed carbonyl-ene reactions is proposed and discussed. 

Another type of reactivity is due to the enhanced nucleophilicity of the hydroxyl group of o-iodosobenzoic acid. For example, o-iodosobenzoic acid reacts with silyl triflate or other silyl sulfonates to afford O-substituted sulfonates [56]. 

The resulting propargylic alcohol is protected as TIPS ether by a standard procedure using the corresponding silyl chloride and imidazole in DMF. Optionally the more reactive silyl triflate and 2,6-lutidine may be employed in order to shorten the reaction time. Under acidic conditions TIPS and TPS are nearly stable protecting groups. Therefore the TBS ether is selectively cleaved with acetic acid even in presence of the acetal moiety.13 Subsequent reaction with iodine and triphenylphosphine, known as the Appel reaction14, provides the desired iodide 4. 

Silyl triflates may also be used as the catalyst to the same goal. In both cases, conjugated base induces desilylation to create the ylid (compare with the action of tetrabutylammonium fluoride on the same imine which led to the anion see Section VI.B.6.a).333,391... 

Among these groups (siloxy, amino, benzotriazolyl, thiolate, cyanide) the methoxy group has been the subject of a large number of studies. To generate the azomethine ylid, essentialy three reagents have been utilized silyl triflate (or iodide), trifluoroacetic acid and lithium fluoride (sometime combined with sonication). Thermal rearrangement has also proven to be efficient. 

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