Butyldimethylsilyl triflate

N-Oxides 986 are transformed by tert-butyldimethylsilyl triflate 987 into the reactive intermediates 988, which rearrange in the presence of methyllithium in THF, followed by PhMgBr in toluene via 989, to 990 ]77, 77 a]. Subsequent work demonstrated that the intermediates 989 react with Me3SiCN 18 in the presence of TiCl to give the a-cyanoamines 991 ]78]. Likewise, the N-oxide 992 affords, with 18 in the presence of 986, the a-cyanoamine 993 in 63% yield. The N-oxide 994 is, furthermore, converted by MesSiCN 18 in 61% yield into the a-cyanoamine 995, whereas the N-oxide of tribenzylamine 996 is converted by 18, 78% yield, into the a-cyanoamine 997 [78, 79] (Scheme 7.24). 

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... 

Selective cyclization of an alkenyl imine is catalyzed by trimethylsilyl triflate (Scheme 76).329 /-Butyldimethylsilyl triflate ( BuN SiOTf) catalyzes imino Diels-Alder reactions of TV-phenyl-aromatic aldimines to afford exo adducts preferentially.330 When A1C13 is used instead of Bufv SiOTf, endo adducts are obtained predominantly. 

The /3-electrophilic additions of pentaamineosmium(ll) complexes bearing various 4,5-tf -coordinated pyrroles to carbonyl compounds have been reported by Harman and co-workers (Scheme 78). 1 1-Methylpyrrole complex, when reacted with benzaldehyde or its dimethylacetal in the presence of /-butyldimethylsilyl triflate (TBSOTf), afforded the corresponding aldol adduct 177 as a 1 1 ratio of diastereoisomers. Pyrrole, 1-methylpyrrole, or 2,5-dimethylpyr-role osmium complexes reacted with an excess of acetone in the presence of TBSOTf to give the O-silylated 377-pyrrolium aldol adducts 178, which may serve as intermediates for various other reactions. 

The category Id cyclization has also been applied to 4-aminoindoles of the type found in the indolelactam tumour promoters such as lyngbyatoxin A and pendolmycin. In a synthesis of analogues of lyngbyatoxin A the isoxazoline 8.4A was constructed as a key intermediate ]. Reductive cleavage of the isoxazoline ring generated 8.4B which was cyclized by reaction with terf-butyldimethylsilyl triflate (Entry 6, Table 8.1). The cyclization of a thioamide was a key step in the synthesis of pendolmycin[5] (Entry 7, Table 8.1). 

Intramolecular cyclization of a, -enamide esters Reaction of the a,(3-en-amide (1) with either trimethylsilyl triflate (1 equiv.) or t-butyldimethylsilyl triflate (1 equiv.) and N(C2H5)3 at 15° results in the benzo[a]quinolizidine 2 in high yield. 

This sultam can also be used to obtain enantiomerically pure (2R,2S)-anti-aldols 19). Thus reaction of 2 with t-butyldimethylsilyl triflate (TBDMSOTf) and N(C2H5)3 provides the (Z)-O-silyl-N,0-ketene acetal 7, which reacts with aldehydes in the... 

The reaction of methyl nicotinate with / -butyldimethylsilyl triflate gave the A-silylpyridinium salt which on treatment with phenyl Grignard followed by TBAF afforded the N-unsubstituted 4-phenyl-l,4-dihydropyridine <1998TL9275>. An improved preparation of iV-(trimethylsilyl)pyridinium triflate, A-(triphenylsilyl)pyridinium triflate, and A-(triisopropylsilyl)pyridinium triflate involves the reaction of the corresponding allyl silanes with triflic acid followed by pyridine <1997S744>. 

Asymmetric intramolecular double Michael reaction.3 Treatment of the 8-phenylmenthyl ot,(3-unsaturated amide ester (2) with r-butyldimethylsilyl triflate and triethylamine effects this Michael reaction with almost complete diastereose-lectivity to give the indolizidine 3, which was used for synthesis of (- )tylophorine (4). 

Thexyldimethylsilyl chloride (bp 55-56 01.3 kPa) and the corresponding tri-flate have been recommended152 as cheaper substitutes for rm-buty[dimethylsilyl chloride and /er/-butyldimethylsilyl triflate. Thexyldimethylsilyl ethers are formed at comparable rates and they are at least 2-3 times more stable than TBS ethers to acid and base hydrolysis but they introduce unwelcome clutter to NMR spectra, Thexyldimethylsilyl ethers are usually prepared by reaction of the substrate with thexyldimethylsilyl chloride in pyridine151 or in DMF in the presence of imidazole.153... 

The key step in a short synthesis of ( )-tylophorine77 is an intramolecular double conjugate addition reaction. Reaction of the ( , )-unsaturatcd ester 1 (R2 = 8-phcnylmcnthyl) with ferf-butyldimethylsilyl triflate in the presence of excess of triethylamine in dichloromethane produces an 80 20 inseparable mixture of the indolizidines 2A and 2B78. Treatment of a mixture of 2A and 2B (R2 = 8-phenylmethyl) with sodium hydride in refluxing tetrahydro-furan for 2.5 hours gives the single indolizidine 2 A. Dioxanyl ester 1 furnishes, on reaction with... 

Simple organosilicon Lewis acids, for example trimethylsilyl triflate (la) [5], trimethylsilyl nonaflate (2) [6], iodotrimethylsilane [7], fert-butyldimethylsilyl triflate (Ic) [8], triisopropylsilyl triflate (Id) [8], etc., are commercially available, but because of their easy hydrolysis and the appearance of traces of a protic acid during storage. 

Later, this cycloaddition reaction was improved by the pretreatment of the enamide ester with an equimoler amount of trialkylsilyl trifluoromethanesul-fonate and triethylamine at ambient temperature. The synthesis of tyro-phorine (119) was achieved by the above improved method (Scheme 55). The enamide ester 441 was subjected to annulation using t-butyldimethylsilyl triflate and triethylamine at 15°C to produce the bicyclic lactam 442 in 68% yield. Oxidation of 442 with thallium(III) trifluoroacetate and boron triflu-oroetherate in a mixture of dichloromethane and trifluoroacetic acid at 4°C produced (83%) the pentacyclic compound 443. Hydrolysis of 443, followed by decarboxylation of the resultant acid, gave the pentacyclic lactam 444. Reduction of 444 with sodium bis(2-methoxyethoxy)aluminum hydride in refluxing dioxane afforded tyrophorine (119) (85CC1159). 

To a mixture cooled at 0°C containing 2.34 g (8.15 mmol) of 3-methoxy-2-pyridyl p-D-glucopyranoside in 50 mL of dry pyridine was added dropwise 2.1 mL (8.97 mmol) of t-butyldimethylsilyl triflate over 15 min. The resulting mixture was stirred at 0°C for another 15 min at which time TLC indicated the silylation was completed. After 3.1 mL (27... 

The Sn-0 bond in the alkylperoxytin compounds will in all probability show the same substitution and addition reactions as it does in alkoxytin compounds, but few studies of these reactions have been reported. In the air, hydrolysis occurs, and the stannyl peroxides, ROOSnBu3, have been shown to react with electrophiles such as triphenylmethyl chloride, methoxymethyl chloride, t-butyldimethylsilyl triflate, and acyl halides or acid anhydrides to give the peroxides R00CPh3, ROOCH OMe, ROOSiMeaBu1, and ROOCOR, respectively. 137-146... 

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