Cyclization of 1,5-dicarbonyl compound

Cyclization of 1,5-dicarbonyl compounds with nitrogen nucleophiles leads to the six-membered aromatic heterocycle pyridine. 

Thiopyrans are prepared similarly by the intramolecular cyclization of 1,5-dicarbonyl compounds in the presence of a thionating reagent (e.g., Scheme 117) . 

There are few reports in which the 5-lactone ring is constmcted through a samarium iodide-mediated reductive cyclization of 1,5-dicarbonyl compounds. In the first example. Fang, Tsai et al. have reported the synthesis of 5-lactones using samarium... 

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See also in sourсe #XX -- [ ]

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