Carbon-nitrogen multiple bonds

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

Carbon-nitrogen multiple bonds in fluorinated imines and nitriles react with halogen fluoride reagents Imines provide 7V-chloroamine.s on reaction with chlo rme fluoride [62, 121, 122, 123] (equations 23 and 24) or with cesium fluoride and chlorine [124] and A -bromoammes on reaction with cesium fluoride and bromine (equation 24)... 

Carbon and fluorine can be added to carbon-nitrogen multiple bonds, generally in highly fluorinated substrates. Perfluoromethanimine adds fluoride ion to give perfluoromethanamiiie ion, which will react with acid fluorides or with another... 

The stereoselective allylation of carbon-nitrogen multiple bonds have also been studied. The addition of allylzinc bromide to aromatic imines derived from (. S j-valine esters was affected by reversibility, which caused the lowering of the diastereoisomeric ratio with increasing reaction time. The retroallylation reaction could be avoided by performing the reaction in the presence of trace amounts of water or by using CeC - 7H2O as the catalyst with a decreased reaction rate.71... 

The insertion of unsaturated molecules into metal-carbon bonds is a critically important step in many transition-metal catalyzed organic transformations. The difference in insertion propensity of carbon-carbon and carbon-nitrogen multiple bonds can be attributed to the coordination characteristics of the respective molecules. The difficulty in achieving a to it isomerization may be the reason for the paucity of imine insertions. The synthesis of amides by the insertion of imines into palladium(II)-acyl bonds is the first direct observation of the insertion of imines into bonds between transition metals and carbon (see Scheme 7). The alternating copolymerization of imines with carbon monoxide (in which the insertion of the imine into palladium-acyl bonds would be the key step in the chain growth sequence), if successful, should constitute a new procedure for the synthesis of polypeptides (see Scheme 7).348... 

N-Substituted carbene complexes show y(CN) absorption in the 1470-1620 cm 1 range of the IR spectrum. These data are consistent with the crystallographic evidence for substantial carbon-nitrogen multiple bonding in these compounds. 

A similar inference about the importance of the metal can be drawn from the differences in behavior with carbon-nitrogen multiple bond systems m... 

Addition of silyl radicals to carbon-nitrogen multiple bonds has mainly been investigated by EPR spectroscopy [9,66]. 

Radical cyclizations to carbon-nitrogen multiple bonds resemble additions to carbon-carbon multiple bonds in that they usually give products of irreversible exo cyclization. To date, the most useful acceptors have been oximes189 and nitriles,190 and one example of each type of cyclization is given in Scheme 45.191 Nitriles are useful because the intermediate imines are readily hydrolyzed by mild acid to ketones. Although this route to ketones is shorter than the two-step sequence of alkyne cyclization/ozo-nolysis, nitriles are slightly poorer acceptors than terminal alkynes, and much poorer acceptors than activated alkynes. Thus, when slow cyclizations are involved, the two-step protocol is preferable. 

Carbon-nitrogen multiple bonds, Grignard additions, 9, 64 Carbon-nitrogen triple bonds... 

Addition of Nitriles to Carbon-Carbon (Michael Addition) and Carbon-Nitrogen Multiple Bonds... 

Compounds with carbon-nitrogen multiple bonds were also successfully used in the Barbier procedure. Allylic groups add to imines in high yields (> 77% in the examples published), even enolizable substrates, possibly due to the low basicity of the medium.37 Additions to nitriles occur in THF in the presence of the zinc-silver couple.38 Terpenic ketones were prepared by this method. 

The nucleophilic nature of these radicals allows addition to carbon-nitrogen multiple bonds, and in selected cases this has been demonstrated. Suitable substrates for such additions include protonated pyridines, thiazoles and imidazoles (equation 183), and nitroalkyl anions359. Yamamoto and coworkers have also described cobalt-mediated multiple additions of carbon tetrahalides, benzyl bromides or a-bromo ketones to isocyanides, which are postulated to occur through the corresponding alkylcobalt(III) complexes360. 

Addition of Organomagnesium Compounds to Carbon-Nitrogen Multiple Bonds, Pages 87-109... 

Substrates containing carbon nitrogen multiple bonds have received somewhat less attention. Nevertheless, imines can be converted to N-silylamines, again with RhCl3(PPh3)3 being one of the most effective catalysts (equation 10). ... 

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