2,2 -Bithienyls structure

Acetylation of 2,3 -bithienyl occurs in the 5-position, which is in accordance with considerations on the localization energies, The structure was proved by hypochlorite oxidation followed by Raney nickel desulfurization of the 5-carboxy-2,3 -bithienyl. ... 

From Bidens species 5-metbyl 5 -butadienyl-2 -bithienyl (245) has been isolated, the constitution of which was eonfirmed synthetically. Another 2,2 -bithienyl derivative has been isolated as an additional nematodicidal principal of the roots of Tagetes, for which strueture (246) has been suggested. On the other hand Sorensen et aL have isolated from the thistles, Berkheya macrocepkala and Echinops spareocephalm, a compound with very similar UV and IR spectra as (246) for which they suggested structure (247), based on... 

X-Ray studies on the structure of 3,3 -dimethoxy-2,2 -bithienyl show the molecule to lie on a crystallographic center of symmetry and the two rings to be in the anti-ioim <1988AXB509>. 

Molecular structure of compounds containing 2,2 -bithienyl fragment 00KGS725. 

Lunazzi et al. have determined the conformation of 2,2 -bithienyl by means of a liquid crystal (nematic phase) NMR study (73JCS(P2)751) they found 78% of s-trans and 22% of s-cis rotamers (the estimated interconversion barrier is about 20 kj mol , see Section 2.9). The same compound using the same approach was studied by Khetrapal and Kunwar (74MP (28)441), the 0 angles determined by X-ray (Section 2.1) and electron diffraction (Section 2.2) are 0° and 34°, respectively they concluded that 2,2 -bithienyl is a mixture of cis- and frans-planar structures but they were unable to calculate the proportions (for theoretical calculations, see Section 2.14.3). 

Compounds 124 and 127 were studied at the lowest ab initio level (STO-3C) to conclude that the structures correspond to fully planar s-cis (both heteroatoms on the same side, sZ) and s-trans forms (sE), the former being the most stable (81 JCS(P2)127). STO-3C and 4-31C calculations were carried out on bifurans 115,116, and 117 by Orti and Tomas (84THE(108) 199), the authors conclude that the sE/sZ preferences depend on the position of the oxygen atoms in the case of 115 the preferred conformation is the sE. A similar conclusion (STO-3C calculations) was reached for bithienyls 119 and 120 where for 118 the most stable conformation is the sE (86JCS(P2)907) in this case the rotational barrier was calculated (25.1 kj mol ) and it agrees with that determined by DNMR (21 8 kJ mol, see Section 2.9). Compounds 115, 118, the Se and Te analogues as well as mixed derivatives were studied at the B3LYP/6-311 ++C(d,p) and... 

Fig. 3 Structures of four donor-acceptor-donor (DAD) oligomers consisting of electron-deficient 2,1,3-benzothiadiazole or quinoxaline moieties linked to electron-rich thienyl or bithienyl units studied in ref. 97. Reproduced with permission from The Royal Society of Chemistry.

A useful method for structure determination of symmetrically substituted 3,3 -bithienyls has been found in the chemical shifts of the methoxycarbonyl protons. The OCHs-resonance in 2- and 3-methoxycarbonylthiophens as well as in 5,5 -dimethoxycarbonyl-3,3 -bithienyls occurred within the small... 

This is nicely seen in the molecular structure of the tizulene carboxylate ester derivative shown in Figure 6.13 [71], Similar structures are found in the solid state for R = phenyl, aryl, thienyl, bithienyl,... 

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