Cyanoalkylation

In order to enhance the reactivity of the chlorine atom, a second reactive monomer can be adopted giving dual cure sites. According to the Hterature, the second monomer can contain carboxyl (22—24), cyanoalkyl (25), hydroxypropyl (26), or epoxy groups (27,28). 

Radicals with adjacent Jt-bonds [e.g. allyl radicals (7), cyclohexadienyl radicals (8), acyl radicals (9) and cyanoalkyl radicals (10)] have a delocalized structure. They may be depicted as a hybrid of several resonance forms. In a chemical reaction they may, in principle, react through any of the sites on which the spin can be located. The preferred site of reaction is dictated by spin density, steric, polar and perhaps other factors. Maximum orbital overlap requires that the atoms contained in the delocalized system are coplanar. 

Thermal or photochemical decomposition of azonitriles (e.g. AIBN) affords o-cyanoalkyl radicals (Scheme 3.71 ).29... 

Absolute rate constants for addition reactions of cyanoalkyl radicals are significantly lower than for unsubstituted alkyl radicals falling in the range 103-104 M V1.341 The relative reactivity data demonstrate that they possess some electrophilic character. The more electron-rich VAc is very much less reactive than the electron-deficient AN or MA. The relative reactivity of styrene and acrylonitrile towards cyanoisopropyl radicals would seem to show a remarkable temperature dependence that must, from the data shown (Table 3.6), be attributed to a variation in the reactivity of acrylonitrile with temperature and/or other conditions. 

The a-cyanoalkyl radicals can, in principle, react with substrates either at... 

However, there are also examples of addition across a strained carbon-carbon single bond, as occurs with bicyclobutane1 and derivatives (Scheme 4.21, Scheme 4.22).180,181 Interestingly, l-cyano-2,2,4,4-letramethylbieylobulane (31) is reported to provide a polykctcniminc (Scheme 4.22).183 This is the only known examples of a a-cyanoalkyl radical adding monomer via nitrogen. 

A closely related procedure for preparing thietane dioxides is the one-step conversion of cyclic a-amino ketoximes (222) to 2-(co-cyanoalkyl)-3-dialkylaminothietane dioxides (226), with trans-orientation of the substituents249 (equation 86). 

Kwiatek and Seyler were the first to report that many organopenta-cyanides, when treated first with acid and then with alkali, liberate nitriles 110). This reaction occurs with unsubstituted primary and secondary alkyl, benzyl, vinyl, and phenyl complexes, while allyl, 2-oxo-, 2-hydroxy-, and 2-alkoxy complexes simply release the organo-ligand on treatment with acid, and 1-cyanoalkyl and a-pyridyl complexes are stable 105) (see also Table IV). The yield of nitrile is usually far from quantitative and is... 

Cyclization of a-cyanoalkyl cyanamides (74) with hydrogen bromide gave 4-aminoimidazoles (77) as their hydrobromide salts. These compounds (77) were found to be unstable as the free base but gave stable (V-acetyl derivatives (84 R2 = Br, R3 = COCH3) (33-82%) when treated with acetic anhydride in pyridine (64JOC153 66CA12211). 

The products can be trapped as a-(cyanoalkyl)amines in the presence of sodium cyanide... 

---