2,3,9,10‐Tetrakis(trimethylsilyl)[5]phenylene. Synthesis via Regiospecific Cobalt‐Catalyzed Cocyclization of 1,6‐Bis(triisopropylsilyl)‐l,3,5‐hexatriyne

Abstract

The highest homologue of the [n]phenylenes thus far isolated, the title compound 1, is a deep-red, extremely air-sensitive crystalline compound. A newly developed strategy for the synthesis of such hydrocarbons has proven to be extremely efficient: cocyclization of tetraethynylbenzene with the hexa-triyne iPr3SiCCCCCCSiiPr3 leads to a [3]phenylene, which, in turn, is likewise a tetraethynyl compound and can thus be employed in renewed cocyclizations.