Triflate trapping reagent

Another triflate ester that recently has found growing application in organic synthesis is commercially available trimethylsilylmethyl trifluoromethanesul fonate. This powerful alkylating reagent can be used for the synthesis of various methylides by an alkylation-desilylation sequence A representative example is the generation and subsequent trapping by 1,3-dipolar cycloaddition of indolium methanides from the corresponding indole derivatives and trimethylsilylmethyl trifluoromethanesulfonate [108] (equation 54)... 

Facile synthesis of simple 3-arylpyrroles from pyrroline by tandem Suzuki dehydrogenation reaction is depicted in Scheme 229. Thus, treatment of l-benzyl-2,5-dihydro-l//-pyrrol-3-yl trifluoromethanesulfonate 1195 (prepared in 55% yield from l-benzyl-3-pyrrolidinone 1194 by trapping the enolate with a triflating reagent), with boronic acid derivatives leads to the formation of 3-arylpyrroles 1196 in good yields (65-74%) <2000TL3423>. 

The oxazolium salt (160), formed from the oxazole (159) by reaction with methyl triflate in acetonitrile, may be reductively ring opened by treatment with phenylsilane in the presence of cesium fluoride to give the azomethine ylide (161) (presumably this species is in tautomeric equilibrium with the corresponding oxazoline). The azomethine ylide can be trapped as an adduct with a suitable dipolarophile, such as dimethyl acetylenedicarboxylate (DMAD). In the case of this reagent the adduct (162) can be ox-... 

The efficient acylbenzyne precursors, [5-acyl-2-(trimethylsilyl)phenyl]iodonium triflates 705 have been prepared by reaction of the appropriate l,2-bis(trimethylsilyl)benzenes with PhI(OAc)2 in the presence of trifluoromethanesulfonic acid in dichloromethane at room temperature. Treatment of these reagents with BU4NF in dichloromethane generates acylbenzynes 706, which can be trapped by furan to give adducts 707 in high yield (Scheme 3.283) [927]. 

To functionalize the C5 position, Williams and Fu developed a 2-phenylsulfonyl substituted oxazole. The C5 position of this oxazole can be cleanly deprotonated with LDA and trapped with either NIS or NBS to form the 5-iodo- or 5-bromo-2-phenylsulfonyloxazole in good yield. The same report details that the 2-phenylsulfonyl group can subsequently be displaced with alkyl, alkenyl, or aryl lithium reagents to form 2,5-disubstituted oxazoles efficiently. A triflate at the C5 position can be prepared from the corresponding oxazolone however, the oxazolone decomposes at room temperature, and Kelly reported that attempted Stille coupling with C5 triflates failed due to decomposition of the triflate. ... 

In the late 1970s, Enders pioneered an elegant method for ketone and aldehyde alkylation involving the use of metalated chiral hydrazones [92, 93). Extensive studies with the (S)-l-amino-2-methoxymethylpyrrolidine (SAMP, 150, Scheme 3.24) auxiliary and its enantiomer RAMP established these as superb chiral auxiliaries with numerous applications. In a typical alkylation sequence, a RAMP/SAMP hydrazine is condensed with an aldehyde or a ketone to form the corresponding hydrazone, such as 152. This can subsequently be deprotonated and the resulting enolate trapped with a variety of electrophilic reagents including alkyl halides, aldehydes, Michael acceptors, silyl triflates, and disulfides. The RAMP/SAMP hydrazine auxiliary may be removed by acidic hydrolysis or ozonolysis to reveal the alkylated... 

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