Alkylthiophene preparation

Oligomeric, (IV), and polymeric alkylthiophenes prepared by Ong et al. (4) were effective as thin-film transistors. 

Alkylthiophene preparation acylation, 401-407 bromination, 407,408/ electrophilic substitution of thiophenes,... 

General Preparation of Regioregular HT Poly(3-Alkylthiophenes) from 2,5-Dibromo-3-Alkylthiophenes Preparation of Regioregular HT Poly(3-Hexylthiophene] (4b)... 

Dibromo-3-Alkylthiophenes Preparation of Regiorandom Poly(3-Hexylthiophene) (5b)... 

In order to characterize poly(3-alkylthiophene) prepared from silylated monomers, room-temperature photoluminescence experiments have been performed on polymers in solution (THF) [132]. Four samples have been studied poly(3-alkylthiophene) synthesized from hydrogenated and silylated monomer, respectively (the polymers are called pATh-1, 1 Table 14.14) and poly(3-alkylthiophene) synthesized from die two isomeric mono silylated monomer pATh-3,4 (Table 14.14). 

Polythiophenes with substituents other than alkyl groups at the 3 position have been prepared by the polymerization of substituted monomers. Many of these polymers have been substituted alkylthiophenes (8) where example side chains are (R =) —(86—89), —OCH (68), —NHC(0) (CH2) qCH (6 )) —0502(0112)30112 (90). Ohiral side chains have also been employed (91,92). Poly(3-alkoxythiophenes) (9) (93—95) and... 

Fatty acids are prepared by acylating thiophene with acid chlorides and reducing the ketones (218) to alkylthiophenes according to Wolff-Kishner or Clemmensen. The latter are then acetylated and oxidized by hypochlorite to 5-alkyl-2-thiophenecarboxylic acids, > ... 

Ni-Catalyzed preparation of regioregular HT poly(3-alkylthiophenes) (HT-388) from 2,5-dibromoalkylthiophenes (389) and Rieke zinc (Zn ) (Chart 2.164). 

R.S. Loewe, S.M. Khersonsky, and R.D. McCullough, A simple method to prepare head-to-tail coupled, regioregular poly(3-alkylthiophenes) using Grignard metathesis, Adv. Mater., 11 250-253, 1999. 

The crystalline composites obtained between poly(3-alkylthiophene) and polystyrene showed an enhanced conductivity (07MM6579). The preparation of regioregular poly(3-alkylthiophene) and perylene diimide derivatives composites have been reported (06MI384). The photoluminescence spectra of this type of composites exhibit a significant photoluminescence quenching of the perylene diimide derivative. This result implies that the light absorbed by the perylene diimide units could also contribute to the generation of current at the photovoltaic device. 

These will be exemplified by series of alkyl, branched and isoprenoidal thiophenes. These methodologies have been used for the preparation and subsequent identification of series of alkylthiophenes comprising a linearly extended phytane skeleton. 

Alkylthiophenes have been known for over one hundred years and the traditional method of preparation was the reaction of suitable 1,4-dicarbonyl compounds with phosphorous trisulfide or pentasulfide (Figure 1). 

This and other older methods, which have been reviewed previously (21, 22), have been largely superceded in the laboratory by more controlled, selective reactions, starting from suitable thiophene precursors. We shall discuss two major reactions which can be used for the preparation of alkylthiophenes electrophilic substitution of thiophenes and the formation and reactions of lithiated thiophenes. For further details and other aspects of thiophene chemistry the reader is referred to previous reviews (21, 22) and references cited therein. Accounts of yearly developments in thiophene chemistry can also be found in the relevant Royal Society of Chemistry publications. 

Acylation. One of the most useful and important methods for preparations of alkylthiophenes is acylation. This is the reaction of carboxylic acids and carboxylic acid chlorides with thiophenes in the presence of a suitable catalyst and leads to 2-acylthiophenes in good yields (typically ca. 60-80% e.g. 23). Reduction of the ketone functionality by either a modified Wolff-Kishner procedure (8, 24) or with a mixed hydride, formed from aluminium trichloride and lithium aluminium hydride (25), yields the alkylthiophene (Figure 6). Alternatively, the ketone group can be alkylated, thereby giving access to 2-(r-alkyl)alkylthiophenes. 

Figure 6. Preparation of 2-alkylthiophenes by acylation and reduction of the resulting ketone.

Examples of the use of acylation in the preparation of alkylthiophenes as standards for organic geochemical studies are given below ... 

Other research groups have made use of the acylation method, followed by reduction of the resulting ketone group, to prepare alkylated thiophenes e.g. C20 alkylthiophenes (8). 

The preparation of 3-methvl-2-f3 7Ur-trimethvldodecvrithiophene. This compound, which has a carbon skeleton resembling that of phytane, is often a major component of certain immature sediments Q). Previous syntheses of this compound have used the acylation method whereby 3-methylthiophene is acylated with 3,7,11-trimethyldodecanoic acid (1, 8). Reference to Figure 5 indicates that the required compound will be accompanied by the 2,4-isomer and this is indeed the case. The pure compound can, however, be prepared using a lithiated alkylthiophene and an aldehyde (Figure 23). 

Authentic standards of both series were prepared using combinations of the techniques outlined earlier. Members of series 1 were obtained by acylation of the necessary 2-alkylthiophene with 3,7,11,15-tetramethylhexadecanoic acid and reduction of the resulting ketone (Figure 25). 

The C21 member of Series 2 was prepared by acylation of 2,4-dimethyl-thiophene with 3,7,11-trimethyldodecanoic acid and reduction of the resulting ketone (Figure 27). The synthesized standards were used for comparison of the mass spectra of, and for GC co-injection studies with, the alkylthiophenes occurring in the bitumen of the northern Apeninnes marl. 

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