Synthesis of silafluorenes by iridium-catalyzed [2 + 2 + 2] cycloaddition of silicon-bridged diynes with alkynes.

[reaction: see text] Silicon-bridged 1,6-diynes underwent [2 + 2 + 2] cycloaddition with alkynes in the presence of an iridium(I)-phosphine catalyst to afford densely substituted silafluorene derivatives. Extended silafluorene skeletons were constructed by the [2 + 2 + 2] cycloaddition of tetraynes.