Carbon-nitrogen bond formation carbonyl compounds

Carbon-nitrogen bond formation, by reductive amination, 59, 1 Carbon-phosphorus bond formation, 36, 2 Carbonyl compounds, addition of... 

For reviews of reactions of carbonyl compounds leading to the formation of C=N bonds, see Dayagi, S. Degani, Y. in Patai The Chemistry of the Carbon-Nitrogen Double Bond Ref. 40, p. 64 Reeves, R.L. in Patai, Ref. 2, p. 600. 

This methodology is also an important and potentially valuable method for C—N bond formation using the amination of carbon nucleophiles with electrophilic nitrogen transfer reagents (Scheme 1) Amination of ordinary carbanions and a-carbanion derived from carbonyl compounds and nitriles provides an important method for the synthesis of amines and a-amino carbonyl compounds and nitriles", respectively. For this purpose, a number of electrophilic amination reagents, which are synthetic equivalents of the R2N+ synthon, have been developed and the synthetic potential of electrophilic amination of carbon nucleophiles has been studied in detail . ... 

The mechanism for enamine formation is exactly the same as that for imine formation, until the last step of the reaction. When a primary amine reacts with an aldehyde or a ketone, the protonated imine loses a proton from nitrogen in the last step of the reaction, forming a neutral imine. However, when the amine is secondary, the positively charged nitrogen is not bonded to a hydrogen. A stable neutral molecule is obtained by removing a proton from the a-carbon of the compound derived from the carbonyl compound. An enamine is the result. 

The various derivatives of carbonyl compounds that involve formation of carbon-nitrogen double bonds at the carbonyl center (see Section 8.1) are not very generally useful as protecting groups. This includes oximes, semicarbazones, and hydrazones. The compounds are usually formed easily enough, but mild conditions for removal are not available. An exception involves the removal of the oxime group by conversion to the acetate ester, followed by chromous ion reduction ... 

The reaction of phosphazenes with carbonyl compounds is an excellent tool for the formation of carbon-nitrogen double bonds and this reaction seems to be one of the most efficient methods for the creation of the imine group under mild reaction conditions. ... 

Recently, 13 was reported to catalyze the asymmetric annulation reaction between allenoates and a,P-unsaturated carbonyl compounds to form substituted 2H-pyrans (Scheme 6.15) [37]. This formal [4+2] cycloaddition afforded exclusively the product with the (E) configuration of the exocyclic double bond, in line with calculations that indicated the ( )-isomer to be about 14.2 kj mol lower in energy than the (Z) isomer. The mechanism of the reaction was formulated as an initial attack by the nitrogen atom of the quinuclidine ring at the allenoate with formation of an ionic intermediate that preferentially reacts at the terminal carbon atom with the a,p-unsaturated carbonyl compound prior to elimination of the catalyst with formation of the 2H-pyran derivative (Scheme 6.15). 

Free-Radical Copolymerization of Vinyl Compounds with Unsaturated Heterocyclic Monomers. Free-radical ring-opening polymerization of cyclic ketenacetals and their nitrogen analogous occurs via formation of carbonyl bond at the expense of a less stable carbon-carbon double bond as depicted in Scheme 14 [49-56] ... 

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