Nucleophilic reactions trimethylsilylacetylene

Additionally, acetylene itself is a useful two-carbon building block but is not very convenient to handle as it is an explosive gas. Trimethylsilylacetylene is a distillable liquid that is a convenient substitute for acetylene in reactions involving the lithium derivative as it has only one acidic proton. The synthesis of this alkynyl ketone is an example. Deprotonation with butyl lithium provides the alkynyl lithium that reacted with the alkyl chloride in the presence of iodide as nucleophilic catalyst (see Chapter 17). Removal of the trimethylsilyl group with potassium carbonate in methanol allowed further reaction on the other end of the alkyne. 

Bromo- and 3-iodo-l,2,4-triazines react with nucleophiles in a similar manner, but more easily than their chloro analogues. For example, 3-iodo-5,6-diphenyl-1,2,4-triazine is converted into 3-(2-trimethylsily-l-ethynyl) -5,6-diphenyl-1,2,4-triazine (61) by action of trimethylsilylacetylene (60) (Scheme 39), whereas no reaction between 3-chloro-5,6,-diphenyl-1,2,4-triazine and acetylene (60) has been observed under identical conditions (84H2245). 

Palladium-Catalyzed Reactions. Numerous nucleophiles react with (l-bromovinyl)trimethylsilane in the presence of palladium complexes. The bromine has been substituted by phenylthio, vinyl, and aryl groups. This approach gives reasonable yields of the desired products. However, the substitution reactions sometimes lack regiospecificity. For example, a mixture of regioisomers was obtained in eq 6. Two mechanisms have been proposed for the formation of the -substituted product. One involves an elimination step to give trimethylsilylacetylene as an intermediate, which then undergoes catalyzed additions with the nucleophile at either the a- or positions. The other mechanism involves the formation of a pentacoordinated palladium intermediate, leading to the formation of isomeric products. ... 

Reaction of Trimethylsilylacetylene/Acetylide with Electrophiles. Deprotonation of TMSA with n-BuLi or Grignard reagents produces nucleophilic acetylides, which can react with various electrophilic carbon centers such as carbonyls, alkyl halides, or epoxides. 

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