Protodesilylation desilylation

Initial protonation of iron in protodesilylation of trimethylsilylferrocene was not, however, favoured as a mechanism by Marr and Webster689, who measured rates by the spectroscopic method using hydrochloric acid in 20 vol. % aqueous methanol (Table 235) and found that the rate of desilylation of the ferrocene compound was little more than that for the 4-methoxyphenyl and 2,4-dimethyl compounds. The similarity of the spread of rates in the different media and the similar activation energies and entropies were considered as evidence that the transition states for reaction of all three compounds were similar. The lower activation energy obtained for the 4-methoxyphenyl relative to the ferrocene compound may arise from the different media involved the difference in entropy seems, however, to be rather larger than one might have expected even allowing for the solvent differences. 

Aza-1,3-dienes. A new route to these useful substrates for [4 + 2]- and [2 + 2]cycloadditions involves protodesilylation of N-l-triethylsilylallylimines such as 1, available in several steps from propargylamine in about 30% yield (equation I). Desilylation of 1 with CsF and 18-crown-6 in THF containing a trace of water... 

Protodesilylation, A new preparation of -unsaturated carboxylic acids involves the amide acetal Claisen rearrangement of a 3-(trimethylsilyl)allyl alcohol such as 1 to allylsilanes (2). Desilylation of 2 by usual methods results in formation of stereoisomers. However, use of liquid HF at low temperatures results only in (E)-3 in 88% yield. The HF-pyridine complex is not so stereoselective. Amides such as 3 can be converted into carboxylic acid esters by Meerwein s trialkyloxonium salts (—70% yield). 

At lower temperature, treatment of this silylated sulfone epoxide 6 with 0.8 equivalents of potassium mrr-butoxide for 4 hours gave a new product, (la,7a,8a)-l-trimethylsilyl-2-thiabicyclo[6.1.0]nonan-7-ol 2,2-dioxide (9), together with unrearranged sulfone epoxide 10 arising from protodesilylation, and the desilylated bicyclic hydroxy sulfone 7 in the ratio 78 16 6. 

Hydrosilylation requires a transition-metal catalyst, such as [HiPtCle], and results in very good yields of the product alkenyl silanes, but often as mixtures of regio- and stereoisomers (2.66). More recently, it has been found that hydrosilylation of internal alkynes using the catalyst [Cp Ru(MeCN)3]Pp6 occurs by trans addition, and this can be followed by protodesilylation to provide a route to E-alkenes. " For example, ruthenium-catalysed hydrosilylation of methyl 2-octynoate with triethoxysilane, followed by fluoride-promoted desilylation of the intermediate regioisomeric alkenyl silanes, gave ( )-methyl 2-octenoate (2.67). 

Both (bromo- and (iodoethynyl)trimethylsilane undergo base-induced desilylation, followed by decomposition, when subjected to Cadiot-Chodkiewicz coupling conditions. Switching to the more stable (bromoethynyl)triethylsilane affords good yields of the terminal diynes after protodesilylation (eq 4). ... 

Both ends of the oligomers could be functionalized as shown in Scheme 3.18. However, the a,(0-bis-terminal alkynes 68-70 showed increasingly low yields in the couplings with 59. Therefore, we used a stepwise procedure (Scheme 3.19) of tail functionalization, followed by protodesilylation, to afford 80-82. The use of TBAF alone for the desilylation... 

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