Dialkylamino radicals

The spin adducts of free radicals and MNP or DMPO were observed by means of an ESR spectrometer. The data of hyperfine splitting constants were compiled in Tables 9 and 10 [40-42,44,45]. ESR studies on the initial free radicals revealed that the monoalkylamino radical RHN-, dialkylamino radical R2N-, and aminomethyl radical -CH2N< or aminoethylidene radical >N( CHCH3) were obtained from the corresponding primary, secondary, and cyclic tertiary amine. In case of a tertiary diamine such as TMEDA, formation of... 

Recently dialkylamino radicals have been generated by direct photolysis of the corresponding tetrazenes in liquid cyclopropane solution at low temperatures (255) ... 

This reaction has not been confirmed. For dialkylamino radicals, reactions such as 27 and 28 would be expected. 

It is possible that dialkylamino radicals participate in the oxidation reactions of some tertiary aliphatic amines (8), but such reactions are mainly speculative. 

Intra- and inter-molecular substitution reactions (55) and (56) involving the dialkylamino radical cations formed from protonated N-haloamines are well known and are based upon the initial work of Hofmann (1883) and of... 

Neutral Amino Radicals. It is generally accepted that dialkylamino radicals add to olefins very reluctantly. This is a little surprising because thermodynamic calculations, based on the best thermochemical values (39), indicate that the addition of NH2 to ethylene ought to be exothermic by about 17 kcal/mole. The apparent lack of reactivity suggests therefore that there is a relatively high activation barrier to this reaction. Indeed, this was found to be the case in the ab initio SCF-MO-CI calculation of the potential surface of the NH2 plus ethylene... 

As seen before, the radical cation of dimethyl sulfoxide (CH3)2SO has been detected by ESR spectroscopy among other radicals when DMSO glasses at 77 K are submitted to y-irradiation28. It has also been reported in pulse radiolysis experiments30 (Table 6). Constant current electrochemical oxidation of bis(dialkylamino)sulfoxides (R2N)2SO gives rise to radical cations which have been detected by ESR spectroscopy33. 

An extensive study132 has been presented on the polarizability effects of alkyl groups in RX moieties (R = Me, Et, i-Pr and i-Bu X = CH2, S, SO2, O and N) in families of weak acids and on the stabilities of adjacent anions and radicals in DMSO solution. Some of the results related to the 9-(dialkylamino)fluorenes are given in Table 12. The increases in acidity are believed to be caused by the progressive increases in anion stabilizing... 

Styrene and indene derivatives (Scheme 2, Y = Ph) are dimerized to l,4-dimethoxy-l,4-diphenylbutanes or 1,4-diphenylbutadienes (Table 7, numbers 1 and 2) [52]. The product distribution is in some cases strongly dependent on the anode potential and the supporting electrolyte. Dimerization is promoted by a-substituents that stabilize the intermediate radical cation, for example, phenyl, vinyl, alkoxy, dialkylamino groups. IJ-Alkyl substituents strongly decrease the yield of dimers and favor formation of dimethoxy-lated monomers. 

Synthetic Suitability of (Dialkylamino)benzene Cation-Radicals... 

Attack at the 2-position has been effected with stabilized radicals such as benzyl and triphenylmethyl. Substitution has also been observed with alkylthio, phenylethynyl and thienyl radicals since the latter two are very reactive, substitution occurs at both positions 2 and 3 (73US295). Thiophene can also be homolytically aminated with amino cation-radicals, leading to 2-dialkylamino derivatives (74AHC(16)123>. 

Polyphenylsilane, (PhSiH) , can be derivatized by free-radical hydrosilylation in the presence of a radical initiator. Alkenes, ketones and aldehydes react readily, to replace up to 93% of the Si-H bonds. This route can be employed to make polysilanes with hydrophilic groups, such as hydroxy, amino and carboxylic acid functions.43 Dialkylamino substituted polysilanes, made by the anionic polymerization of masked disilenes (see equation (17)), when treated with acetyl chloride give chloro-substituted poly silanes. The chlorine can then be displaced by other nucleophiles.27... 

A-[(A, A -Dialkylamino)alkenyl]benzotriazoles have been shown to be useful precursors to oc-amino radicals, which can subsequently undergo both 5-exo- and 6-exo ring closure on to a,p-unsaturated esters or nitriles.85 For example, exposure of benzotriazole 79 to Sml2 afforded cis-cyclopentane 80 in 70% yield (Scheme 5.52). The mechanism of the cyclisation is believed to involve dissociation of the benzotriazole, thereby generating an iminium cation, which undergoes rapid reduction to the a-amino radical in the presence of Sml2 (Scheme 5.52).85... 

---