Cyano-compounds

It has been stated that many halogen-free compounds, e.g., certain derivatives of pyridine and quinoline, purines, acid amides and cyano compounds, when ignited on copper oxide impart a green colour to the dame, presumably owing to the formation of volatile cuprous cyanide. The test is therefore not always trustworthy. The test is not given by duorides. 

Mild acid converts it to the product and ethanol. With the higher temperatures required of the cyano compound [1003-52-7] (15), the intermediate cycloadduct is converted direcdy to the product by elimination of waste hydrogen cyanide. Often the reactions are mn with neat Hquid reagents having an excess of alkene as solvent. Polar solvents such as sulfolane and /V-m ethyl -pyrrol i don e are claimed to be superior for reactions of the ethoxy compound with butenediol (53). Organic acids, phenols, maleic acid derivatives, and inorganic bases are suggested as catalysts (51,52,54,59,61,62) (Fig. 6). 

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

Unsaturated hydrazones, unsaturated diazonium salts or hydrazones of 2,3,5-triketones can be used as suitable precursors for the formation of pyridazines in this type of cyclization reaction. As shown in Scheme 61, pyridazines are obtainable in a single step by thermal cyclization of the tricyanohydrazone (139), prepared from cyanoacetone phenylhydrazone and tetracyanoethylene (76CB1787). Similarly, in an attempted Fischer indole synthesis the hydrazone of the cyano compound (140) was transformed into a pyridazine (Scheme 61)... 

Starting from the assumption that the geometry relaxation after excitation is of primary importance with respect to the luminescence response, we decided to employ a solid polymer matrix to suppress conformational changes of the oligomers. For the measurements, dilute blends with polysulfone as the transparent host matrix were prepared. In Figure 16-13, the PL decay curves for the two cyano compounds in both chloroform and polysulfone are presented, as are the PL spectra of Ooct-OPV5-CN in chloroform and polysulfone [69J. 

The 8-cyano compound 2 is prepared by condensation of the disodium dithiolate 1 with disulfur dichloride.414... 

The tendency to undergo valence isomerization is generally of fundamental importance regarding the stability of the compounds. In the case where an equilibrium exists between the eight-membered ring and the bicyclo[4.2.0]octatriene, decomposition may readily occur by a [2 + 2] cycloreversion process, particularly if molecular nitrogen or a cyano compound can be eliminated. 

Method A TiCl4 CH,Cl,. Method B BF3-0(C,H5),/CH2C1,. b Determined by GC of the protected alcohols for cyano compounds or, for 2-propenyl compounds, by LC of the free alcohols. 

For a review of the acidity of cyano compounds, see Hibbert, F. in Patai Rappoport The Chemistry of Triple-bonded Functional Groups, pt. 1 Wiley NY, 1983, p. 699. 

The mechanism of formation of pyridines from a,P-unsatuiated nitriles and active cyano compounds has been investigated. These processes proceed through a Michael adduct which undergoes a regioselective cyclization to the corresponding pyridine <96H(43)33>. 

Cyanations of quinoline 877 and isoquinoline N-oxide 879 in DMF or N-methyl-pyrrolidone provides the cyano compounds 878 and 880 in 90 and 79% yield, respectively (Scheme 7.4) it was expected, e.g., that pyrimidine N-oxides would react analogously [6]. 

In view of the observations of the ionic dissociation of nitro-cyano compounds, it is hardly surprising that even a hydrocarbon could dissociate ionically into a stable carbocation and carbanion, provided that the medium is polar enough to prevent the recombination reaction and to ensure equilibration. 

As shown in Fig. 3, the observed values of A/fhet(R-R ) in DMSO for the hydrocarbons [3-2] and [25-2] are 15kcalmol less than the values predicted from (28) and (29), respectively, while A/fi,et(R-R ) for the nitro-cyano compound [4-102] in acetonitrile (30) is close to the value predicted from (29). Therefore, this departure of the dissociative hydrocarbons from the predicted behaviour can be ascribed to steric congestion in the hydrocarbon, predominantly caused by the carbanion moiety [2 ]. 

The AGhet(R-R ) values observed in acetonitrile are almost identical with A//het(R-R ) values for the compounds [4-6] and [5-6] (Troughton et al., 1984). Thus, provided that this is the case also for a nitro-cyano compound, (tri-t-butylcyclopropenyl)(phenyl)malononitrile [101-102], its AGhet(R-R ) value should be close to the A//het(R-R ) value predicted from (29). In practice, as indicated in Fig. 3, the AG°het(R-R ) observed in acetonitrile is 6kcalmol less than that predicted (Miyabo et al., 1993). Hence this departure from linearity can be most probably ascribed to steric congestion, which is mainly derived from the cation moiety [lOT ] in [101-102]. 

B. From Cyano-compounds and Phosphorus(v) Halides.—Continued reports of the reactions of alkyl cyanides with phosphorus pentachloride appear. With dicyanides the formation of phosphazenes occurs via a series of intermediates whose stability varies with the nature of X ... 

The spectral data for a further group of donor-acceptor aminoazoben-zenes are given in Table 2.3. The valence-bond approach may be used to provide a good qualitative account of the data in the table. Some relevant resonance structures, which may be used to explain the 2max values of cyano compounds 16a-d, are shown in Figure 2.9. 

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