Thiophene-based derivatives

A novel thiophene-based molecular scaffold that could be used for optical in vivo imaging of protein aggregates was recently reported by Aslund et al. [36]. This chemically defined anionic pentameric thiophene derivative, p-FTAA (Fig. 21a), could be utilized for direct in vivo detection of A [S deposit in the brain of a transgenic mouse model with AD pathology. The deposits were easily visualized by two-photon... 

The key step in the preparation of a novel class of condensed thiophene based GABA receptor inverse agonists was the cross-coupling of the bromo derivative of the parent system. The 2-pyrrolyl substituent, for example, was... 

Over the last few decades there has been much interest in the thiophene-based systems and considerable effort has been expended in many laboratories on various aspects of their chemistry, including synthesis, structural studies and theoretical calculations and predictions. X-Ray analysis of the crystal structures of thieno[3,2-6]thiophene (3) (49AX356), selenolo[3,2-6]selenophene (4) (69AX(B)1374) and thieno[3,2-6 jfuran derivative (5) (79CC366) have been reported. 

As in previous years, thiophene based diarylethene derivatives constitute an important class of materials which are considered as promising candidates for various kinds of optoelectronic devices, such as switches and optical memories. 

Density functional theory (DFT) calculations of two types of push-pull chromophores built around thiophene-based 7t-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions (Figure 6) have been carried out to assign the relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores <2003CEJ3670>. 

Dinucleating macrocyclic SBs derived from the condensation of thiophene-2,5-dicarbaldehyde with different diamines have been prepared in their uncomplexed state.186 Considering the [2+2] product (63) of Scheme 17 with (58) as head unit, the different lateral chains of the thiophene-based macrocycles that have been prepared are R = (CH2)3, (CH2)4, (CH2)s, (CH2)6,... 

One-pot syntheses of annulated derivatives of furan, pyrrole, pyridine, pyrane, and thiophene based on reactions of quinones with enamines 04YGK811. 

A facile and efficient synthetic route to densely substituted thiophenes based on base induced cyclization reaction between thioamides derived from morpholine and a-haloketones has been reported. Thus, the thioamides 4 were subjected to treatment with the haloketones 5 (R = H, Ar, Me) under basic conditions to provide the tetrasubstituted thiophenes 6. Likewise, the reaction was also demonstrated to give good yields of thiophenes when the haloketones were replaced with 2-bromo-3-oxobutyric acid derivatives or propargyl bromide <04T6085>. 

Niphatesines A-H (4-11). Niphatesines A-D (4-7) showed antineoplastic activity and they were found in another Niphates species from the sea around Okinawa [123]. The total synthesis of 4-7 has been approached by two different research groups. A first regio/enantioselective synthesis was achieved (see Scheme 1) by making use of the extremely versatile Pd(0) chemistry, which assisted the 3-pyridine alkylation in the key step. At the same time the absolute configuration of niphatesin C (6) and D (7) was established [24]. A different, thiophene-based approach was used to complete the total synthesis of both enantiomers of niphatesin C (see Scheme 2). In this case the absolute configuration was established on the basis of the comparison of the sense of optical rotation with that of the natural product [25]. Niphatesin A (4) was also synthesized in a simple manner via an alkyne derivative (see Scheme 6). 

A series of naphthodithieno[3,2-l)]thiophene-based (NNTT) semiconductors were synthesized (140CF333) and their optical and electrochemical properties characterized. As shown, the first important step involves a palladium-catalyzed Suzuki of the thiopheneboronic acid. Subsequent FeCl3-catalyzed oxidative cyclization affords desired NDTT derivatives. 

All systems can in principle be regarded as annulene derivatives and many of them have been prepared from this viewpoint. With the development of conducting polymers and organic electronics, more recently emphasis has rather been put on the design of thiophene-based macroeycles which are model systems and show interesting electronic properties. 

In addition, lyoda et al. reported the synthesis of variants of tetra(2,3-thienylene) which are planar, in contrast to Marsella et al. s derivatives [369]. With respect to thiophene-based [12]annulene 4.9, which was first synthesized by Kauffmann et al. in low yields, Marsella s group extended this scaffold by preparing... 

J. M. Raimundo, P. Blanchard, N. GaUego-Planas, N. Mercier, 1. Ledoux-Rak, R. Hierle and J. RoncaU, Design and synthesis of push-puU chromophores for second-order nonUnear optics derived from rigiditied thiophene-based jt-conjugating spacers, J. Org. Chem., 67, 205-218 (2002). 

Thiophene-based Materials for Electroluminescent Applications 739 Table 19.5 EL data for devices based on dibenzothiophene-S,S-dioxide derivatives 125 and 126... 

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