Insertion nitrogen-carbon bond

The skeleton of daphnilactone A-type alkaloids seems to be constructed by the insertion of a Cl imit into a nitrogen -carbon bond in the daphniphylline-type skeleton followed by lactonization. 

Peroxyacetic acid Insertion of oxygen into nitrogen-carbon bonds... 

Without additional reagents 2,4-Dienecarboxylic acid amides from cyclopropenones and enamines Insertion of 3-C-atoms into nitrogen-carbon bonds... 

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... 

Figure 5.16 Photoactivation of a phenyl azide group with UV light results in the formation of a short-lived nitrene. Nitrenes may undergo a number of reactions, including insertion into active carbon-hydrogen or nitrogen-hydrogen bonds and addition to points of unsaturation in carbon chains. The most likely route of reaction, however, is to ring-expand to a dehydroazepine intermediate. This group is highly reactive toward nucleophiles, especially amines.

Recently an arsenic amide derivative has reacted with an isocyanate, adding across the carbon—nitrogen double bond. I think this is the first example of a group V element which seems to be undergoing an insertion reaction. 

The methylene fragment also reacts with undecomposed diazomethane to form nitrogenous products. Many other reactions, including insertion in carbon-hydrogen bond (cf. the photochemical reaction of diazomethane with ether and with 2-propanol183 occur. 

Carbon dioxide does not insert into all metal-carbon bonds, as demonstrated by the lack of reaction with [HIr(PMe3)4CH2CN]+ 137). Similarly, benzylchromium complexes failed to insert C02 142), and in the reaction of Me(Me2N)2W=W(NMe2)2Me with C02, the molecule inserts into the metal-nitrogen bonds, but not into the metal-carbon bonds 143). 

Silicon-carbon and silicon-nitrogen multiply bonded compounds 1019 insertion compound 712 (55% yield) (equation 236). 

Attempts to understand the mechanism of C02 fixation and reduction in photosynthesis gave rise to the study of photoinsertions of C02 by simple model compounds such as A1(TPP)(C2H5) [112] and In(Por)(CH3) [113], frhere Por = TPP or OEP. For these complexes it was found that both visible light absorption and coordination of a nitrogen donor base (e.g. 2-methyl imidazole, Melm, or pyridine, py) in an axial position are required for the insertion of C02 into the metal-carbon bond. 

In recent years, amines have also been synthesized by nitrogen insertion into a zirconium-carbon bond followed by hydrogenolysis [75] (Scheme 28). 

A selective sampling of the photochemical cycloaddition and cyclization chemistry of 2H-azirines has been outlined in this chapter. Some photochemical sequences increase molecular complexity more than others, but each seems to provide complex heterocyclic structures in a very efficient manner. Indeed, many of these photoreactions rapidly construct hetero-polycyclic systems that are difficult to produce in other ways. In contrast to their photochemical behavior, the major thermal reaction of 2H-azirines generally involves C(2)-N bond cleavage to form vinyl nitrenes which further react by either insertion into an adjacent C-H bond or else undergo addition across a neighboring rc-bond. The 27i-electrons of the carbon-nitrogen double bond of 2H-azirines can also participate in thermal symmetry-allowed [4- -2]-cycloadditions with a variety of substrates. It is clear from the above discussion that the chemistry of 2H-azirines is both mechanistically complex and... 

In the following section we shall consider the insertion of carbon dioxide into transition nieial carbon, metal hydrogen, metal -oxygen and metal -nitrogen bonds. 

Reactions with other carbon triple bonded functional groups. The substitution of nitrile for alkynes does not lead to pyridines or quinolines in the benzannulation reaction.Instead noncyclic products are obtained that are the result of insertion of the carbon-nitrogen triple bond into the metal-carbene bond. On the other hand, in a very recent report it was found that X -phosphaalkynes will undergo the benzannulation reaction to produce phosphaarene chromium tricafbonyl complexes. 

Carbene reactions provide a versatile approach to the synthesis of five-membered nitrogen-containing rings. Of particular importance here are intramolecular insertion of a carbene into C — H and N — H bonds, addition onto multiple carbon-carbon bonds, intermediate formation of ylides as a result of carbene addition onto the heteroatom followed by rearrangement, cycloaddition, and cyclization. 

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