Of unsaturated nitrogen heterocyclic

The Chemistry of Unsaturated Nitrogen-Heterocyclic Compounds Containing Carbonyl Groups... 

G. A. Lee, Simplified synthesis of unsaturated nitrogen-heterocycles using nitrile betaines, Synthesis (1982) 508-509. 

The generation of the carbcxi-carbon double bond of unsaturated nitrogen heterocycles by the rDA reaction of cycloadducts that act as protected ethylenes has been accomplished. Azetines have been prepared by this method. Another example is the synthesis of l-methyl-3-pyrroline (201). By protecting the ethylene of N-methylmaleimide (199) with furan and then reducing with lithium aluminum hydride, adduct (200) was obtained (equation 86). Pyrolysis of adduct (200) at 250-300 C gave l-methyl-3-pyrroline (201) in 60% isolated yield. The ethylene moiety of N-substituted maleimides can also be generated via rDA reactions. Examples include the generation of N-phenylmaleimide (equation 87) and of N-acetoxymaleimide (equation 88). ... 

Catalytic hydrogenation of unsaturated nitrogen heterocycles plays an important role in the synthesis of nitrogen-containing natural products such as alkaloids and amino acids. 

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