- Protected Acetylenics
- Click Chemistry
Alkynylsilanes as discussed here are those wherein the silyl moiety is directly bonded to the sp-carbon of the triple bond. They are also oftentimes referred to as silylacetylenes. Alkynylsilanes such aspropargylsilanes are, therefore, not included.
Acetylene chemistry has been extensively reviewed over the years. Several of the more recent additions are noted here.1
The vast majority of applications of 1-silylacetylenes occur where the silyl group, typically trimethylsilyl, serves as a group for the protection of the reactive terminal C-H bond. Supporting this silyl protection strategy is the fact that it is quite easy to remove the silyl group in high yield under a variety of mild conditions that are tolerant of other functional groups. A further advantage of the terminal silylacetylenes is that the presence of the silyl group, for both steric and electronic reasons, can often influence the regio- and stereochemistry of reactions at the triple bond. Finally, the trimethyl-silyl group has its own reactivity in the final product of a reaction at the triple bond. These often result in the generation of a vinylsilane unit, which can be further reacted under a number of conditions including protiodesilylation to generate the parent olefin.2
A report of an explosion using ethynyltrimethylsilane in an oxidative coupling under Glaser-Hay conditions was reported.3 The cause of the explosion was attributed to static electricity between the syringe needle used to introduce the copper catalyst and a digital thermometer inside the flask and not the thermal instability of the silane. It is interesting to note that the trimethylsilyl group can impart stability to alkynyl systems. A good example of this is bis(trimethylsilyl)-1,3-butadiyne, which shows excellent thermal stability compared to the parent 1,3-butadiyne. A flash explosion of trimethylsilylpropyne during a bulk transfer from a metal drum has also been reported and was shown to be associated with static discharge.