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Organic metals : studies related to the synthesis of acceptors derived from TCNQ

University of British Columbia

Since a report that the complex of TTF.TCNQ showed novel solid state properties including high room temperature conductivity, there has been considerable interest in the study of these so called "organic metals." This thesis describes the synthesis of new acceptors derived from TCNQ. First the synthesis of 2-methoxycarbonyl-7,7,8,8-tetracyanoquino-dimethane (56) is presented. Bromination of methyl 2,5-dimethylbenzoate followed by treatment with sodium cyanide yielded the dicyano compound 60 which was converted to the dihydro-TCNQ 62 via the corresponding phenylenetetracyanodiacetate intermediate. Oxidation of 62 afforded 2-methoxycarbonyl-7,7,8,8-tetracyanoquinodimethane (56), which was found to be unstable. The synthesis of 2,3-dimethoxycarbonyl-7,7,8,8-tetra-cyanoquinodimethane was attempted in the following manner: the Diels-Alder cyclization of trans,trans-2,4-hexadiene and dimethyl acetylenedi-carboxylate followed by dehydrogenation of the adduct gave dimethyl 3,6-dimethylphthalate. Benzylic bromination of this material followed by displacement of the bromines by cyanide yielded the dicyano compound 73. However, several attempts to convert 73 to the corresponding tetraester 78 were unsuccessful. The synthesis of 2,3-dimethyl-7,7,8,8-tetracyanoquinodimethane is presented. The intermediate 2,3-dimethylcyclohexane-l,4-dione (87) was prepared from 2,3-dimethylphenol by standard means. It was then condensed with malononitrile, and the product was treated with bromine/pyridine to give the dihydro-DMTCNQ 89. When this compound was treated with a mixture of palladium and sulfur at 180°C the desired 2,3-dimethyl-TCNQ 83 was obtained in low yield. The second part of this thesis describes the preparation of 11,11, 12 ,12-tetracyano-4,5,9,10-tetrahydropyreno-2,7-quinodimethane (TCNTP) from mesitylene. This compound was bisbrominated to give 3,5-bis-(bromomethyl)toluene, which was then coupled with 3,5-bis(mercaptomethyl)-toluene to produce the dithia[3.3jmetacyclophane 98. This was converted to the dimethyl[2.2]metacyclophane 96 via Wittig rearrangement followed by reduction with lithium in liquid ammonia. This cyclophane was then brominated and the resulting dibromo compound was converted to the corresponding dicyano-94. The latter compound was treated with bromine in the presence of iron powder to produce 2,7-bis(cyanomethyl)-4,5,9,10-tetrahydropyrene. Introduction of the remaining two nitrile groups was accomplished via use of the tetracyanodiacetate intermediate 92. Hydrolysis and decarboxylation of 92 followed by oxidation with NBS/triethylamine at -78°C furnished the desired TCNTP (90).

Text

2010-03-02

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http://hdl.handle.net/2429/21367

Chemistry

University of British Columbia

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