Silanes as Protecting Groups for Terminal Alkyne

Because trialkylsilyl groups are very commonly used to protect the terminal C-H of an alkyne, pro- tiodesilylation back to the parent alkyne is an important transformation. This can be accomplished with a number of mild reaction conditions. Among these is the simple reaction of the alkynyltrimethylsilane with K₂CO₃/MeOH or, for more hindered silanes, TBAF/THF. Examples of these are to be found throughout this short review. The selective protiodesilylation of an alkynylTMS group in the presence of an alkynylTIPS group with K₂CO₃/THF/MeOH illustrates the potential for selective protection/deprotection.⁴

Bis(trimethylsilyl)-1,3-butadiyne was selectively relieved of one of the trimethylsilyl groups by reaction with MeLi/LiBr in diethyl ether.

Bis(trimethylsilyl)-1,3-butadiyne was metalated with one equivalent of MeLi and reacted with acrolein and subsequently protiodesilylated to yield vinyl diynyl carbinol 1. The trans metalation with five equivalents of MeLi and reaction with acrolein gave the diol 2 in excellent yield. These key intermediates were carried forth in syntheses of (+)- and (-)-falcarinol and (+)- and (-)-3-acetoxy falcarinol.⁵