Amidines reactions with enaminones

In a recent publication, amidine derivatives of a cyclic enaminone are used as the heterodiene component in a Diels-Alder reaction with diethyl maleate to yield 5-quinolones203 (equation 145). 

In an intramolecular reaction with, , A -diethylformamide or JV,JV-dimethylacetamide diethyl acetal, enaminones are known to react at the nitrogen to form amidines. The corresponding products from acetamide acetals can be converted to 2-aminoquinolines by condensation with DMF acetals or to 1,4-dihydroquinolines by cycloaddition with diethyl maleate (see Section II.A.5) (equation 26). 

Benzopyrano[3,4-with amidines or guanidine under basic conditions. Scheme 177 (86JHC1753). 

Amino-l,2,4-oxadiazolcs (11) arc excellent sources of amidines. When they are treated with 1,3-dicarbonyl derivatives they are converted into enaminones (12), which cyclize to imidtizolcs in the presence of bases (Scheme 2.2.5). This reaction utilizes the well-known general attack of a nucleophilic group in the side chain at N-2 of the oxadiazole ring. Yields of 2-acylamino-4-acylimidazoles usually lie between 60 and 80% [21]. The free amino derivatives are readily isolated after acid hydrolysis. 

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