Synthesis of High Carbon Materials from Acetylenic Precursors. Preparation of Aromatic Monomers Bearing Multiple Ethynyl Groups1

The synthesis of polyethynyl aromatics as starting materials for the preparation of highly cross-linked organic solids containing high atom fractions of carbon is described. Treatment of bromoand iodoaromatic compounds with (trimethylsily1)acetylene (TMSA) in the presence of palladium(0) and copper(1) in amine solvents yields (trimethylsily1)ethynyl-substituted aromatics. The TMS protecting groups can be removed by hydrolysis with mild base. Compounds prepared by using this technique include 1,3-diethynylbenzene, 2,5-diethynylthiophene, 1,3-diethynyltetrafluorobenzene, 1,4-diethynyltetrafluorobenzene, 2-ethynylthiazole, 2,4-diethynylthiazole, 2,7diethynylnaphthalene, hexakis((trimethylsilyl)ethynyl)benzene, tetraethynylthiophene, 2,5-bis((trimethy1silyl)ethynyl)-3,4-bis(3-hydroxy-3-methyl-l-butynyl)thiophene, 2,5-diethyny1-3,4-bis(3-hydroxy-3-methyl-l-b~tynyl)thiophene, 2,5-bis(4-(2-thienyl)butadiynyl)-3,4-bis(3-hydroxy-3-methyl-l-butynyl)thiophene, and 2,5-bis(4-(2-thienyl)butadiynyl)-3,4-diethynylthiophene.