Thienyl groups

Of interest in this connection is a study of the UV spectra of chal-cones of the general type A——CO—where A and B are 2-thienyl, 2-furyl, and phenyl in all combinations. The 2-thienyl group causes a bathochromic shift in both the A- and B-positions,... 

A study of the rearrangement of pinacols of the general type (177) has elegantly demonstrated the capacity of the thienyl group to supply... 

On the other hand, the electron-attracting properties (—I and —M) of the 2-thienyl groups should also facilitate prototropic reactions, where the rate-determining step is the removal of a proton from the a-carbon and which thus is facilitated by electron-attracting sub-... 

It is thus obvious that the 2-thienyl group is both a better electron donator and electron acceptor than the phenyl group, facilitating both nucleophilic and prototropic reactions at the a-methylene carbon. 

The carbonyl group reactivities in thiophenes and benzenes are very similar, as shown by the similar rates of alkaline hydrolysis of esters and by the great similarity of the thiophenealdehydes to benzaldehyde in numerous carbonyl group reactions. This has been ascribed to the counteracting —I- -M effects of the thienyl group in this kind of reactions. ... 

Benzyl and heteroaryl (e.g., furanyl or thienyl) groups can be cleaved from the tin under basic conditions also, and nucleophilic attack on the tin is now assisted by attack of the solvent (e.g., water) on the organic group, through a transition state of the type HO—H—R— SnRgOH (99-101). 

The synthesis of luminescent organoboron quinolate polymers (21) (Fig. 15) via a three-step procedure starting from a silylated polystyrene has been communicated. The synthesis was initiated by the highly selective borylation of poly (4-trimethylsilylstyrene) (PS-Si), followed by the replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl). In the final step, the 8-hydroxyquinolato moiety was introduced. The hexyl-substituted polymers efficiently emitted light at 513-514nm upon excitation at 395 nm.40... 

Figure 33 shows the UPS spectra of 2,5-bis(diphenylmethy-lene)-2,5-dihydrothiophene and di-hydroselenophene, as compared with that of 2,5-bis(dithienyl methy-lene)-2,5-dihydrothiophene, together with the spectra of benezene and thiophene for references, irrespective of the central ring with sulphur or selenium the UPS spectra are found to be almost same. However, the spectra were significantly different with changing the substituent rings at the exocyclic double bonds from the phenyl to the thienyl groups. In both the phenyl and the thienyl substituents, the spectra are very similar to those of benzene and thiophene... 

From thses results, it is considered that the dihydrothiophene substituted with thienyl groups is more favorable for the donor to the acceptor of C18TCNQ rather than the other dihydrothiophene and selenophene. 

Tetrakis(2-thienyl)allene reacted smoothly with TCNE at room temperature to form the [4 + 2]-cycloadduct. One of the thienyl groups was incorporated as the part of the diene [172],... 

These reagents are qualitatively similar to other cuprates in reactivity, but they are more stable than the dialkylcuprates. Because cyanocuprate reagents usually transfer only one of the two organic groups, it is useful to incorporate a group which normally does not transfer. The 2-thienyl group has been used for this purpose.9 In a mixed alkyl-thienyl cyanocuprate, only the alkyl substituent is normally transferred as a nucleophile. 

Synthesis. In attempts to further extend the 7i-system of the metal dithiolene core of 2a, Amb and Rasmussen reported the preparation of a 2,2 -bithiophenedithiolate ligand to synthesize [Bu4N][4a] (Seheme 3) in 2007. The resulting anion 4a represents a funetionalized analogue of 2a, with the %-system extended through the a-thienyl groups coupled to the exterior a-positions of the 2a core. This initial synthetic approach was then optimized and used to produce a series of extended metal thiophenedithiolene eomplexes 4a-e as shown in Scheme 3. ... 

Hessen and co-workers discovered that the reaction of ethylene with [Cp 2La(C4H3S)]2 (prepared from [Cp 2LaH]2 and thiophene) in the presence of thiophene formed thienyl-capped PE, H(CH2CH2)42-C4H3S) (e.g., 80 °C, ethylene 7.5 atm, activity = 27 g-polymer mmol-La h , 4/ =1300, PDI = 1.4). They revealed that C-H activation of thiophene was the only chain-transfer mechanism that is in operation, and that all of the PE chains produced under the conditions they examined were capped on one side by a thienyl group. 

Michael addition of the carbanion flanked on one side by a 3-thienyl group, and on the other by a sulfoxide or a sulfone, to chalcone has been reported (81TL5097). Cyclization of the resultant anion with a suitable ortho-substituent is followed by elimination to give a benzo[6]thiophene derivative (Scheme 105). 

An unusual result was noted with this reagent. If steric demands are pushed to a severe level, then 1,2-addition of the thienyl group is observed.50 The reasons are not clear, but a solution to the problem is the addition of BF3-Et20 to the reagent.56... 

The use of a 2-thienyl group as a nontransferable ligand in lower order cuprates has been described, H. Malmberg, M. Nilsson and C. Ullenius, Tetrahedron Lett., 1982, 23, 3823. 

Figure 4-23. Copper-promoted formation and hydrolysis of closely related imines containing thienyl groups.

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