Fused nitrogen heterocycles

Tdndem reducdon-Michdel ddchdon using sidtdblysubsdnitedi juteto dryl-fused nitrogen heterocycles fEq. 10.79. ... 

The Bunce group disclosed a straightforward domino process for the construction of aryl-fused nitrogen heterocycles by employing a combination of a reduction and a Michael addition [20]. The transformation involves an initial Fe-mediated reduction of nitroarenes 7-38, furnishing an aniline which undergoes a subsequent... 

Scheme 7.13. Synthesis of aryl-fused nitrogen heterocycles.

Acridine and its derivatives are also fused nitrogen heterocycles similar to acridones, which display a high fluorescence quantum yield and possess the ability to intercalate tightly, though reversively, to the DNA helical structure [73], with large binding constants [74]. As a result, acridine dyes are recognized in the field of the development of probes for nucleic acid structure and conformational determination [75-77]. 

Tandem reduction-Michael addition using suitably substituted nitroarenes provides a general route to aryl-fused nitrogen heterocycles (Eq. 10.79).135... 

A variety of cyclic olefins (5-, 6-, and 7-membered) that contain nitrogen have been prepared via ring-closing metathesis, for example as shown in Eq. 33 [209]. Other examples are shown in Eqs. 34 [210] and 35 [211]. A variety of pyrrolizi-dines, indolizidines, quinolizidines, pyrrolidinoazocines, piperidinoazocines, and other fused nitrogen heterocycles have also been prepared via ROM (e.g., Eq.36 [212,213]). 

The preparation of fused nitrogen heterocycles such as pyrrolizidines, indolizidines, quinolizidines, pyrrolidinoazocines and piperidinoazocines by the RCM of appropriate dienes (equation 38), is another case where presence of a ring assists the RCM reaction. However, when n = 7 (with x = 1), the C=C bonds, separated by 11 single bonds, are too far apart for RCM to occur. Applications of this general strategy are in prospect for the formation of fused nitrogen heterocyclic systems in problems of alkaloid synthesis240. 

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