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摘要
A new rational pathway to 2,7-difunctionalised--hexa-substituted triphenylenes is presented, requiring less protection/deprotection and purification steps than more conventional synthetic procedures in the framework of the biphenyl route%26apos;. Main improvements are deprotection via alkaline hydrolysis of an ester in ethanol/water medium instead of using toxic and pyrophoric reagents like lithium diphenylphosphide, and the use of easily prepared brominated precursors instead of iodinated reagents for biphenyl synthesis. 4,4-Diacetoxy-3,3-bis(hexyloxy)biphenyl has been synthesised under this scheme, and characterised by proton nuclear magnetic resonance (H-1 NMR) spectrometry, elemental analysis and single-crystal crystallography. It crystallises in the P-1 space group, and exhibits a layered structure built-up through dipolar, C-H ... and C-H ... O=C non-covalent interactions. This compound has been oxidatively coupled with 1,2-bis(hexyloxy)benzene to yield 2,7-dihydroxy-3,6,10,11-tetrakis(hexyloxy)triphenylene, a non-mesogen key precursor for the synthesis of the corresponding liquid-crystalline 2,7-difunctional triphenylenes. Indeed, a reactive 2,7-difunctional mesogen was prepared and used to produce new triphenylene-siloxane hybrid monomeric, trimeric and polymeric mesogens. All of them exhibited columnar hexagonal (Col(h)) mesophases.
- 出版日期2013-8-1
