Carbon-nitrogen bonds intermolecular additions

Unlike many other type of radical addition reactions, the product is most often an alkyl-cobalt(III) species capable of further manipulation. These product Co—C bonds have been converted in good yields to carbon-oxygen (alcohol, acetate), carbon-nitrogen (oxime, amine), carbon-halogen, carbon-sulfur (sulfide, sulfinic acid) and carbon-selenium bonds (equations 179 and 180)354. Exceptions to this rule are the intermolecular additions to electron-deficient olefins, in which the putative organocobalt(III) species eliminates to form an a,/ -unsaturated carbonyl compound or styrene353 or is reduced (under electrochemical conditions) to the alkane (equation 181)355. 

In these reactions, the nitrogen nucleophile is typically an amide, carbamate, or sulfonamide. Because of the low nucleophilicity of such nitrogen functions, no intermolecular 1,4-addition involving C—N bond formation is known. In all cases reported, the carbon-nitrogen coupling takes place in an intramolecular aminopalladation. 

This chapter deals with recent advances in efficient radical traps and also includes newly developed radical acceptors for both intramolecular and intermolecular addition. Special attention will be given to the synthetic importance of newly developed heteroatom radical traps, particularly carbon-nitrogen double bonds. 

Aromatic nitrogen heterocycles display considerable medium shifts (Section 3.1.4). Carbon-13 shifts of pyridine decrease in a but increase in [i and y position upon addition of water (Fig. 4.12). The dilution effect is explained in terms of intermolecular hydrogen bonding between pyridine and water [99]. 

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