Alkylation coordinated nitrogen atoms

Alkylation of coordinated nitrogen atoms has also given rise to new chelate rings and coincidentally to macrocyclic structures (equations 43 and 44).167,16S More recently, the alkylation technique has been extended to phosphorus (equation 45).169 A more recent novel free radical cyclization... 

The chelate ring closure described in equation (42) 66 would be represented by a more concerted version of the general type shown by equation (35). The final product (63) has also been treated with a,a -dibromo-o-xylene to produce the related macrocycle, via its complex. Alkylation of coordinated nitrogen atoms has also given rise to new chelate rings and coincidentally to macrocyclic structures (equations 43 and 44). " More recently, the alkylation technique has been extended to phosphorus (equation 45). A more recent novel free radical cyclization... 

In addition to complexes of type 44 with a C2 coordinated NHC ligand, complexes of type 45 with abnormal C4 or C5 bound carbene ligands have recently been described (Fig. 16) [143, 144]. The carbene carbon atom in these complexes is stabilized by only one nitrogen atom. A similar situation has been observed for the cyclic (alkyl)(amino)carbene (type 16, Fig. 6) [38, 39]. 

In these reaetions, the most reliable mechanism is considered to involve the initial metal-coordination at the nitrogen atom of the pyridine ring and the subsequent attack of an alkyl or aryl anion at the most probable cationic sites on the ring, namely, the 2- and/or 4-position of the ring. If a 2-halogen substituted pyridine is used, the nucleophilic anion attacks the 6-position. Thus, the addition is a more prefered reaction than the ipso-substitution as shown in reaction (29). The substitution of amide or phenyl-... 

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