Transforming the Conjugated Backbone: from Oligofurans to Oligonaphthalenes

Oligoarenes are conjugated aromatic backbones which constitute an important class of organic compounds, with promising applications in organic electronics and catalysis. While the synthesis of unsubstituted oligophenylenes was recently demonstrated,^[1] the introduction of monodispersed functionalized oligoarenes in a highly-selective manner remains a significant challenge. Oligofurans, which are oxygen-containing analogs of the intensively studied oligothiophenes, were recently introduced as a new class of organic electronic materials.^[2] Unlike oligothiophenes, oligofurans can undergo Diels-Alder cycloaddition, and we were therefore interested in utilizing their reactivity for the introduction of new π-conjugated backbones.

Herein we report the conversion of long oligofurans to oligonaphthalenes, by multiple Diels-Alder cycloadditions with benzyne precursors.^[3] Consequent deoxygenation of the formed cycloadducts resulted in the formation long oligonaphthalenes, containing up to 6 units. This reaction, with formation of up to 12 new carbon-carbon bonds in a single step, represents a unique example for the conversion of long π-conjugated backbones, while retaining the π-conjugation.

References:

[1] A. Abdulkarim, F. Hinkel, D. Jansch, J. Freudenberg, F. E. Golling, K. Mullen, J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b10254.

[2] O. Gidron, M. Bendikov, Angew. Chem. Int. Ed. 2014, 53, 2546-2555.

[3] S. Phatangare, O. Gidron, in preparation.