This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Hexaarylbenzenes (HABs) are precursors to hexabenzocoronenes, which exhibit liq. cryst. and light-harvesting properties. Several analogs have been prepd. that are highly sym. substituted, either with six identically substituted aryl groups or with two differently substituted aryl groups. Recently, hexaarylbenzenes with four different aryl substituents have been prepd., but in an ABCDDC substitution pattern which allows selective elaboration of the HABs at the ortho positions. Herein we report the synthesis of heterosubstituted hexaarylbenzenes with an AABCCD substitution pattern. The general synthetic strategy involves the condensation of a diarylacetone with a substituted benzil to give a tetraarylcyclopentadienone, which can then undergo a Diels-Alder cycloaddn. with a diarylethyne to give the hexaarylbenzene. However, because both the benzil condensation and Diels-Alder cycloaddns. are not regioselective, we have synthesized asym. diarylacetones that give hexaarylbenzenes which have two different substituents at the para positions. Asym. Collman carbonylative coupling of two benzyl bromides gives the asym. diarylacetones in decent yields, which have then been condensed with benzil and further elaborated to give the heterosubstituted HABs.
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