Imidoyl anions

Trimethyl((V-phenylbenzimidoyl)stannane reacts with halides such as benzyl or allyl bromide, benzoyl chloride, or methyl iodide in the presence of KF and 18-crown-6 to give the corresponding ketimine presumably attack of the fluoride ion at tin gives an imidoyl anion equivalent73... 

Imidate esters can also be generated by reaction of imidoyl chlorides and allylic alcohols. The lithium anions of these imidates, prepared using lithium diethylamide, rearrange at around 0°C. When a chiral amine is used, this reaction can give rise to enantioselective formation of 7, 8-unsaturated amides. Good results were obtained with a chiral binaphthylamine.265 The methoxy substituent is believed to play a role as a Li+ ligand in the reactive enolate. 

Imidoyl esters (Scheme 3.7) are obtained readily when the appropriate imidoyl chloride is reacted with an alcohol or phenol under basic conditions in the presence of phase-transfer catalysts [71]. The reaction with thiophenol yields the corresponding thioimidoyl ester. Diaroyl amides are produced by the analogous reaction of the imidoyl chloride and carboxylate anions. In this reaction, the initially formed carboxylic ester undergoes a 1,3-migration to produce the amide. 

Included in this section are the conversions of azepin-2-ones to imidoyl chlorides and to thiones, as these processes may be viewed as nucleophilic attack by halide or sulfur anions on the modified 2-hydroxyazepine. 

Imidoyl halides react with NH- and NHa-containing compounds to give amidinium salts, which were sometimes isolated,but the hree amidine bases were usually prepared from them. Since amid-ines are converted by water-free acids to the corresponding amidinium salts, amidinium salts with nearly every desired anion are accessible by this procedure. The alkylation of A/A(, -trisubstituted amidines, as well as those of symmetrically IV.lV -disubstituted, IV-monosubstituted and A(-unsubstituted amidines are unambigous reactions. By this method a lot of amidinium salts, e.g. (145), (146) and (147) (equation 87), have been prepared. The alkylation of A -monosubstituted and N,Ar-unsymmetrrcally substituted amidines can give rise to product mixtures of amidinium salts. 

Though very stable thermally, aziridine 31 slowly decomposes at 220°C, producing imidoyl fluoride 195 and amine 196 in a 1 1 ratio in 95% yield. A likely course of events entails reversible ring opening to azomethine ylide 197, which abstracts a fluoride ion from the starting aziridine to form anion 198 and cation 199 (akin to 179 above). Ring closure of 199 yields 200, and then transfer of a proton from 200 to 198 gives the final products. 

The mechanism of the reductive defluorination of perfluorinated N F amines may involve a relatively low laying LUMO of N—F bond. The injection of an electron on this orbital leads to the formation of radical anion D, which can further lose fluoride anion, forming radical E. The reduction of E to azaanion F followed by second fluoride anion elimination may lead to the corresponding cyclic imidoyl fluoride as a result of reductive defluorination (Scheme 9.1). 

The presence of highly electrophilic C=N bond defines the reactivity of this class of compounds. Similar to other perfluorinated imidoyl fluorides, cyclic analogues are sensitive to the action of nucleophiles. For example, compounds 81 and 124 react with metal fluoride anion in polar solvents with the formation of the salt 125, which can react with a strong electrophiles (Fig. 9.38). 

It is noteworthy, that in contrast to noncyclic perfluorinated imidoyl fluorides RfN = CFR f, cyclic imines 124 and 81 undergo the dimerization upon treatment with fluoride anion (Fig. 9.40). 

Diaryl or arylalkyl imidoyl chlorides react with the acyltetracarbonylferrate anions (67) at room temperature in CH2CI2 to give the mesoionic l,3-oxazol-5-ones (68) in isolated yields of 37—65%. The anion (67) is generated in the normal way by reaction of [Fe(CO)s] with sodium amalgam followed by reaction with the appropriate acid chloride at -30 °C. The mesoionic compounds (68) are useful intermediates since they react with alcohols to give a-amino-acids and undergo a variety of cycloaddition reactions to form new heterocycles. 

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