Desilylations silver® fluoride

In the presence of two equivalents of silver fluoride, N-protected bis[(trimethylsi-lyl)methyl]amines lead also to azomethine ylids which can be trapped by dipolarophiles. The mechanism of the cycloaddition reaction involves sequential electron-Me3Si+-electron transfer process from the amine to silver fluoride, which forms silver metal, ruling out a fluoride-induced desilylation process. Although silver is recovered at the end of the reaction, a cheaper oxidizing reagent is still lacking.448,449... 

Conceptually it would be possible to prepare N-silylmethyliminium salts by the addition of an electrophile to the p carbon of N-silylmethylenamines [Eq. (5)]. The reaction of l-(trimethylsilylmethyl)indoles with silver fluoride is reported to be initiated by the addition of silver cation to the 3-position to form N-silylmethyliminium fluoride 44, whose desilylation by fluoride ion leads to azomethine ylides 45 (86JA1104). This is the only example known for the reaction depicted by Eq. (5). The narrow application of this method may arise from the lack of a general preparation for N-silylmethylenamines. 

The non-silylated triple bond in derivatives such as 211 is reduced preferentially , and because of the ease with which the alkynyl-silicon bond is cleaved, a route is made available for the selective reduction of the internal triple bond of polyynes which also contain terminal alkyne linkages. Desilylation can be accomplished with dilute base , silver nitrate or fluoride salts . An example which illustrates the sequence is the conversion of 211 to 212 in 53% yield . 

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