Cyano-group, alkyl stabilization

Nucleophilic radical, R and activated alkyl iodides, R l, which have electron-withdrawing groups, react smoothly through a SOMO-LUMO (a ) interaction to form RI and stable R as shown in Table 1.17. Here, the formed Rf is stabilized through the resonance effect by an ester or a cyano group [74]. 

Our approach was to design molecules with appropriate properties (perpendicular orientation, solubility, and chemical stability). Thus, we synthesised a,(o-dicyano-P,P -dibutylquaterthiophene (DCNDBQT) as the molecular semiconducting layer. While the short alkyl chain should improve the solubility, the a,(o-substituted cyano groups were introduced to enable lamellar stacking (see Scheme 5.1). 

Nucleophilic Substitutions. 7V,7V-Dimethyldithiocarbamoyl-acetonitrile (1) serves as an active methylene compound, because its carbanion is stabilized by sulfur and cyano groups. It can be alkylated stepwise in aqueous sodium hydroxide under phase transfer catalysis (eq 1). The anion undergoes nucleophilic aromatic substitution to give nitroarenes, with elimination of the dithiocarbamate group (eq 2). Nucleophilic addition of (1) to phenyl isothiocyanate also occurs readily. ... 

Olefination of the Aldehyde 178 using a stabilized Wittig reagent followed by protecting group chemistry at the lower branch and reduction of the a,p-unsaturated ester afforded the allylic alcohol 179 (Scheme 29). The allylic alcohol 179 was then converted into an allylic chloride and the hydroxyl function at the lower branch was deprotected and subsequently oxidized to provide the corresponding aldehyde 161 [42]. The aldehyde 161 was treated with trimethylsilyl cyanide to afford the cyanohydrin that was transformed into the cyano acetal 180. The decisive intramolecular alkylation was realized by treatment of the cyano acetal 180 with sodium bis(trimethylsi-lyl)amide. Subsequent treatment of the alkylated cyano acetal 182 with acid (to 183) and base afforded the bicyclo[9.3.0]tetradecane 184. 

The nomenclature of the RP is not consequent. The RP most often used contains octyl (RP C8) or octadecyl (RP C18) groups. There is no differentiation even when two methyl groups are introduced additionally with the silane (as with monofunctional silanes) or only one (difunctional) or none (trifunctional silane). Some manufacturer use silanes with bulky side groups (e.g., isopropyl groups) to improve the hydrolytic stability of the bonded phases, but here also, only the longest alkyl group is used in nomenclature. RP C8 and RP C18 are the work horses in HPLC. Shorter chains (RP4) are used in protein separations, and special selectivity can be obtained with bonded phenyl, cyano, amino or fluoro groups. 

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