Tetrathia helicenes

Both X-ray crystallographic studies and theoretical predictions have been done to show that these sexithiophenes take a helical conformation. Internal torsional forces between rings have been used to drive the molecule to take a solid state helical conformation. Synthesis of tetrathia-[7]-helicene (TH[7]) 85 has been carried out by McMurry coupling of 2-formyl-benzo[l,2-i 4,3-... 

Table 4. 2ft), ft)) of substituted tetrathia-[7]-helicenes as a function of the number and position... 

Licandro, Froni, and coworkers have also employed the oxidative photocyclodehydrogenation approach for the synthesis of new enan-tiopure tetrathia-[7]-helicene diphosphine derivative 14 (05SL1137, 06S3670, 11EJ05649). A notable feature of this method lies in the fact that the key tetrathia-[7]-helicene scaffold can be easily and regioselectively... 

The method consists of the one-step synthesis of (Z)-l,2-(bis-benzo-dithienyl)ethenes 10 using double Suzuki coupling between stereochemi-caUy defined diboronic acid esters 11 and 2-iodo-benzodithiophene 12. The (Z)-alkenes thus obtained can be easily and efficiently photochemicaUy cyclized to the corresponding substituted tetrathia[7]helicenes. This methodology can also be applied to the synthesis of stilbenoid derivatives with two different heterocyclic systems such as the phosphole 13 (Figure 3) (2014CEJ12373). 

Symmetrical and unsymmetrical benzo-fiised tetrathia[7]helicenes substituted with electron-donor (ED) and electron-acceptor (EA) substituents, and containing the maleimide functionality, which imparts the right cis stereochemistry for the efficient photocycUzation and a higher solubiUty, have been prepared, e.g., 14 15 (Scheme 6). 

The SchoU reaction has recently been developed to synthesize a variety of substituted naphthodithiophene building blocks through DDQ/acid-mediated oxidative cyclizations (2013JO11147). The versatility of the Scholl reaction using the DDQ/acid system is demonstrated by the preparation of the novel substituted tetrathia[7]helicene 30 from the precursor 31, where the three new C—C bonds are formed in a one-pot procedure (Scheme 13). 

Films of tetrathia[7]helicene 1 and tetrathia[7]helicene 72 were deposited at 25 °C under vapor-phase conditions on a bare silica surface (Si02), and on a silanized one with hexamethyldisilazane (HMDS) (20090E1511). AFM... 

Few apphcations of thiaheHcenes in biology are so far available, and most of them involve DNA binding with tetrathia[7]helicene derivatives. A first report shows that (/ -2,13-bis(dimethylaminomethyl)-tetrathia[7]heHcene has a propensity for a highly enantioselective binding to Z-DNA, thus effectively converting B-DNA into Z-DNA (2004JA6566). 

Fig. 1 Chemical structure and names of representative compounds presenting large first hyperpolarizabilities, l,3,5-tris(pyridylethynyl)benzme (1), 2- 4-[3,5-dimethyl-l-(2-propylheptyl)-l/f-pyridin-4-ylidene]-3,5-dimethylcyclohexa-2,5-dienylidene malononitrile (TMC-2, 2), l-(2-hydroxyethyl)-2-[2 -(4"-W,iV-dimethylaminophenyl)ethenyl]benzothiazolinium (3), E, ii)-3,3 -(7,8-di-n-propyl-tetrathia[7]helicen-2,13-di-yl)di-acrylonitrile (4), 2-(3-eyano-4-((E)-2-(5-(4-dimethylamino)-styryl)thiophen-2-yl)vinyl)-5-phenyl-5-(trifluoromethyl)furan-2(5H)-ylidene)-malononitrile (YL156, 2-(5-methyl-3-(4-(pyrrolidin-l-yl)styryl)cyclohex-2-enylidene)malono-nitrile (MH2,...

Bossi A, Licandro E, Maiorana S, Rigamonti C, Righetto S, Stephenson GR, Spassova M, Botek E, Champagne B (2008) Theoretical and experimental investigation of electric field induced second harmonic generation in tetrathia[7]helicenes. J Phys Chem C 112 7900... 

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