M-Quinodimethane

Six-membered mesoionic heterocycles of the m-quinodimethane dianion type , Friedrichsen, W., Kappe, T. and Bottcher, A., Heterocycles, 1982, 19, 1083. 

Hehre and co-workers have used this approach for the investigation of biradicals and other reactive neutral molecules. For example, by using the bracketing approach, they were able to determine the proton affinities of o- and p-xylylene (o- and p-quinodimethane (lo and Ip) Figure 5.3), from which they were able to determine the enthalpies of formation of the reactive, Kekule molecules. They found the proton affinity of the meta isomer to be too high to be measured directly by bracketing, but were able to assign a lower limit, and subsequently a lower limit to the enthalpy of formation of the m-xylylene diradicals. 

All discussed Ksem s are related to the separately solvated members of a two step redox system. In solvents of low polarity the charged forms may form ion pairs. Especially prone to this association are anionic redox systems of Type C (RED + OX = 2 SEM ) since the often used gegenions K , Na and Li tend to form ion pairs with the anions. These exhibit special UV/VIS-, NMR- and ESR-spectra as well as g-values Dimeres of the type (SEM M )2 may also be formed, as demonstrated with the anion radicals of pyrazines ° heptafulvalene and tetracyano-quinodimethanes. Corresponding associations are reported for dian-... 

Nakamura Y., O-kawa K., Matsumoto M., Nishimura J. (2000) Separation and characterization of [60]fullerene bisadducts modified by 4,6-dimethoxy-o-quinodimethane, Tetrachedron, 56, 5429-5434. 

Grosch B, Orlebar CN, Herdtweck E, Kaneda M, Wada T, Inoue Y, Bach T (2004) Enantioselective [4+2]-cycloaddition reaction of a photochemically generated o-quinodimethane Mechanistic details, association studies, and pressure effects. Chem Eur J 10 2179-2189... 

Manoharan, M., De Proft, F., Geerlings, P. Aromaticity Interplay between Quinodimethanes and C60 in Diels-Alder Reactions Insights from a Theoretical Study. J. Org. Chem. 2000, 65, 6132-6137. 

Heterocycles have been synthesized using o-quinodimethane chemistry. Thermolysis of l,2-dihydro-jY-(2-propenyl)-1-benzocyclobutadicnecarboxamide gave exclusively the m-fuscd hexahydrobenz[e]isoindol-l -one 31. 

Pappenfus, T.M. et al., A pi-stacking terthiophene-based quinodimethane is an n-channel... 

It is therefore most remarkable that the conversion of the trichloromethyl compound [72] into [73] can be achieved in very good yield with ammonia in aqueous THF at room temperature. As shown below, this reaction presumably starts from the red carbanion formed by proton abstraction, which easily eliminates chloride ion from the a-position forming violet carbanion through quinodimethane. Under the same reaction conditions, perchlorotoluene remains unaltered (M. Ballester and C. Fernandez-Llamazares, unpublished). 

Terzidis M, Tsoleridis CA et al (2005) Chromone-3-carboxaldehydes in Diels-Alder reactions with indole-ortho-quinodimethane. Synthesis of tetrahydrochromeno[2, 3-b]carba-zoles. Tetrahedron Lett 46 7239-7242... 

Inagaki F, Mizutani M et al (2009) Generation of N-(tert-Butoxycarbonyl)indole-2, 3-quinodimethane and Its [4- -2]-Type Cycloaddition. J Org Chem 74 6402-6405... 

Thin layers of PTCBI (50 A thick) and BCP (75 A thick) are used as the EBL in the front and back subcells, respectively, thereby forming a high efficiency double HJ PV structure (Peumans et al., 2000). A CRZ consisting of Ag nanoclusters (-5 A average thickness) buried in a 50 A thick 4,4, 4"-tris(3-methyl-phenyl-phenyl-amino)triphenylamine (m-MTDATA) p-doped with 5 mol% tetrafluoro-tetracyano-quinodimethane (F4-TCNQ) (Maeimig et al., 2004) was employed to connect the two subcells in series, where electrons generated in the front cell and holes generated in the back cell recombine. 

M. Szwarc. The p-quinodimethane molecule. Discuss. Faraday Soc., pages 46-49, 1947. 

Ravi, M. Rao, D.N. Cohen, S. Agranat. L Radhakrishnan. T.P. Strong optieal seeond harmonic generation in a ehiral diaminodicyano-quinodimethane system. J. Mater. Chem. 1996, 6 (7). 11/9. 

---