Carbon-nitrogen compounds 1,2-addition reactions

It has been tentatively suggested that one mechanism underlies the Willgerodt reaction and the Kindler modification of it. A labile intermediate is first formed which has a carbon—carbon bond in the side chain. The scheme is indicated below it postulates a series of steps involving the addition of ammonia or amine (R = H or alkyl), elimination of water, re addition and eUmination of ammonia or amine until the unsaturation appears at the end of the chain then an irreversible oxidation between sulphur and the nitrogen compound may occur to produce a thioamide. 

Huisgen has reported in 1963 about a systematic treatment of the 1,3-dipolar cycloaddition reaction as a general principle for the construction of five-membered heterocycles. This reaction is the addition of a 1,3-dipolar species 1 to a multiple bond, e. g. a double bond 2 the resulting product is a heterocyclic compound 3. The 1,3-dipolar species can consist of carbon, nitrogen and oxygen atoms (seldom sulfur) in various combinations, and has four non-dienic r-electrons. The 1,3-dipolar cycloaddition is thus An +2n cycloaddition reaction, as is the Diels-Alder reaction. 

In addition to using amine oxidation products as mediators, anodic oxidation reactions can be used to functionalize amine compounds. These reactions include both - examples that generate imines and nitriles, as well as examples that lead to the addition of nucleophiles to the carbon alpha to the nitrogen. 

Metal-Nitrogen Compounds. Very little work has been done on addition reactions of metal-nitrogen compounds. The trimethyltin dimethylamide apparently does undergo reactions analogous to those of the trialkyltin alkoxides just discussed. For example, the following reactions were observed with carbon dioxide, carbon disulfide, and phenylisocyanate (57) ... 

Figure G shows some insertion reactions of carbonyl compounds. In the isocyanate and ketene cases, the addition takes place, not to the carbonyl double bond, but to the carbon—nitrogen or the carbon—carbon double bond.

A common method for the preparation of primary amines involves the hydrolysis of isocyanates or isothiocyanates.4 The latter react more slowly and more vigorous conditions are required. The reaction is catalyzed by acids or bases. In this case simple addition of water to the carbon-nitrogen double bond would give an N-substituted carbamic acid (3). Such compounds are unstable and break down to carbon dioxide (or COS in the case of isothiocyanates) and the amine ... 

The coordinated azide undergoes addition reactions with a variety of unsaturated compounds. Thus with carbon monoxide under very mild conditions the azide is converted to isocyanate with the loss of nitrogen (equation 17).293-295... 

The nitrile group in cyanopyridine can participate in intramolecular reactions. The presence in chalcone 118 of an ortho-hydroxyl substituent can lead to its addition to a carbon-nitrogen triple bond, with the formation of the 2/7-pyran-2-iminic moiety (compound 119) [126, 127] (Scheme 3.36). 

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 this case it is not that the carbon-nitrogen bond is so weak rather, it is the formation of the strong nitrogen—nitrogen triple bond of the N2 product that enables the reaction to occur at relatively low temperatures. Azobis(isobutyronitrile), also known as AIBN, has been widely used as a radical source because it is commercially available. In addition, it undergoes bond homolysis at lower temperatures than other azo compounds (below 100°C) because the product radicals are tertiary and are stabilized by resonance. 

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