NEW LIQUID-CRYSTALLINE COMPOUNDS BASED ON 2-ARYLTHIOPHENES AND 2-(BIPHENYL-4-YL)THIOPHENES

被引:29
作者
BRETTLE, R [1 ]
DUNMUR, DA [1 ]
MARSON, CM [1 ]
PINOL, M [1 ]
TORIYAMA, K [1 ]
机构
[1] UNIV SHEFFIELD,DEPT CHEM,SHEFFIELD S3 7HF,S YORKSHIRE,ENGLAND
关键词
D O I
10.1080/02678299308026324
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A general and versatile route to the 2-alkyl-5-(4'-cyanophenyl)thiophenes was established, involving the condensation of an aryl vinyl ketone with an aldehyde in the presence of a thiazolium catalyst (Stetter procedure) to give a 1,4-diketone which with Lawesson's reagent undergoes ring-closure to give the corresponding arylthiophene. In the final step the exchange of a bromo substituent on the phenyl ring for a cyano group is accomplished by copper(I) cyanide in N,N-dimethylformamide at reflux. The same sequence afforded 2-alkyl-5-(4''-cyanobiphenylyl)thiophenes. Several of the 1,4-diketones were obtained by conjugate addition of nitroalkanes to aryl vinyl ketones, and treatment of the gamma-nitroketones with silica gel-supported potassium permanganate. Three alkyl 5-(4-cyanophenyl)thiophene-2-carboxylates were prepared by condensing beta-chlorovinylaldehydes with thioglycolates. The cyanophenylthiophenes exhibited only monotropic phases, but incorporation of an additional phenyl ring provided cyanobiphenylylthiophenes of wide nematic ranges. Transition temperatures of binary mixtures of the cyanophenylthiophenes with 4-n-pentyl-4'-cyanobiphenyl were measured, and extrapolated virtual nematic-isotropic transition temperatures were determined.
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页码:515 / 529
页数:15
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