Dicyano-4-

Several complexes of iron with the 1,1-ethenedithiolates have been isolated. These are mainly tris-Fe(III) complexes with the 1,1-dicyano-2,2-ethylenedithiolate ligand (1). Recently, however, Coucouvanis et al. (262) synthesized a new 1,1-dithiolate ligand (XVIII) from the reac-... 

Zinc-mediated reductive dimerization cyclization of 1,1-dicyano-alkenes occurs to give functionalized cyclopentenes in good yields under saturated aqueous NH4CI-THF solution at room temperature. The trans isomers are the major products (Eq. 10.38).89... 

The behavior described above has been verified by experiment and calculation on numerous substituted dienes and dienophiles. For example Fig. 10.13 shows results for 2°-D isotope effects on Diels-Alder reactions of 2-methyl-butadiene with cyano-ethylene and 1,1-dicyano-ethylene. The calculated and experimental isotope effects are in quantitative agreement with each other and with the results on (butadiene + ethylene). In each case the excellent agreement between calculated and observed isotope effects validates the concerted mechanism and establishes the structure of the transition state as that shown at the bottom center of Fig. 10.11 and the left side of Fig. 10.12a. 

In theoretical work, the initial steps in the polymerization of 1,1-dicyano-, 1,1-difluoro-, and 1,1-dimethyl-cyclopropanes by reaction with H, OH, and Me have been modelled by ab initio methods. " Other ab initio MO calculations for the reactions of H, Me, Ft, j-Pr, and r-Bu with a variety of silanes and germanes have been carried out. The results indicate that the attacking and leaving radicals adopt an almost co-linear arrangement. Bond distances and energy barriers were predicted for the reactions studied. 

Analogously, l,2-dicyano-l,2-diphenylethylene, which is free from steric strains, and its strained isomer l,l-dicyano-2,2-diphenylethylene are reduced at practically the same potentials (Ioffe et al. 1971, Todres and Bespalov 1972). In DMF, with the support of Et4NI, the reversible two-step one-electron reductions are characterized by the following potentials (mercury pool as a reference electrode) -0.48 and -0.98 V for 1,2-dicyanoethylene and -0.50 and -1.07 V for 1,1-dicyano isomer. Thus, electrochemical reduction does not fix the difference in isomer structures. 

Dicyano-1,1 -bicyclohexyl has been prepared previously by Hartman 3 in a similar manner. The procedure has been substantiated by Overberger, O Shaughnessy, and Shalit.4... 

Reduction of—CN and —COOR.3 NaBH4 does not ordinarily reduce nitriles, but it reduces selectively one cyano group of 1,1-dicyano epoxides, that which is trans to an aryl or alkyl substituent. 

The reactions between 1,1 -dicyano-2-p-dimethy laminophenyl-2-fluoroethylene (76) and p-toluidine or phenylenediamines in acetonitrile157 form the substitution products (77) as shown in Scheme 35. The reaction is of the second order in amine when ArNH2 is p-toluidine and it is catalysed by substituted pyridines (and quinolines) in accordance with the presence on the reaction pathway of the zwitterionic complex 78, which is in equilibrium (see equation 14) with the anionic form 79. 

Figure 2 shows the structures of the bifunctional model systems l(n), (n=4,6,8,10,12), investigatedThe synthesis of these systems and a discussion of their electrochemical properties as well as of their electronic absorption and emission spectra have been given elsewhere (Oevering et al., 1987). These molecules contain a 1, 4-dimethoxynaphthalene unit as the photoexcitable electron donor (E./2 =+1.1 V vs. see in acetonitrile) and a 1,1-dicyano-vinyl moiety as a moderately powerful electron acceptor (Ev=-. l V) separated by an array of at least n C-C sigma-bonds. The centre-to-centre separation (Rc) and the edge-to-... 

Butyllithium was freshly titrated by the method of Gilman.2 Excess strong base, either butyllithium or lithium diisopropylamide (LDA), (exceeding 1 equiv per diphenylacetonitrile) should be avoided since the resulting Thorpe-Ziegler cyclization product is susceptible to fragmentation under the reaction conditions to afford 1,1-dicyano-4,4-diphenylbutane. 

Monomethyl-, dimethyl-, and trimethylspiropentanes were transformed into rather complex mixtures of products on thermolysis,but spiropentanes containing one or more electron-withdrawing substituents generally gave good yields of a single methylenecyclobutane (Table 15). The remarkable difference in the products formed from the two isomers of 1,1-dicyano-2,3-dimethylspiropentane was indicative of a dramatic change in the mechanism of thermolysis. 

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