Facile Synthesis of Extended π-Conjugated Compounds by Rhodium-Catalyzed Stitching Reaction

Abstract

π-Conjugated compounds have been extensively investigated as potentially useful organic materials, but accessible structures are currently still limited mainly due to the lack of efficient synthetic methods. In particular, preparation of extended π-conjugation systems often requires tedious synthetic approaches. In this regard, we recently devised a new synthetic strategy “stitching reaction” that allows for a facile access to new types of bridged π-conjugated compounds in a convergent manner under rhodium catalysis. For example, we achieved the first synthesis of ‘quinoidal’ fused oligosiloles from two different oligo(silylene-ethynylene)s, and found that these new π-conjugated compounds exhibit unique electronic properties. In addition, structurally related π-conjugated compounds with other bridging groups such as CO could also be synthesized in a similar fashion through the use of appropriate precursors. We could further expand the utility of this process by developing a new and efficient synthesis of useful π-conjugated compounds such as dibenzo[a,e]pentalenes and fluorene derivatives. Furthermore, this synthetic strategy was successfully applied to the preparation of π-conjugated polymers which cannot be synthesized by using other existing methods. Herein we describe an overview including physical properties of newly synthesized π-conjugated compounds.