Aniline derivatives reaction with diketones

Tu et al. have reported the synthesis of 4-aza-podoplyllotoxin via a three-component reaction of an aldehyde, aniline and cyclic diones in H2O under MWl. Use of tetronic acid as the cyclic diketone provided the 4-aza-podophyllotoxin derivatives (76) (Scheme 6.30). The reaction proceeded via the attack of Schiff s base, formed through the condensation between aldehyde and aniline, on tetronic acid resulting into an intermediate which underwent intramolecular cyclization and dehydration to yield the product. The scope of the strategy was enhanced by replacing tetronic acid with 1,3-indanedione to generate indenoquinoline derivatives (77) [69]. 

Reddy et al. synthesized 5-hydroxyindole derivatives via the Nenitzescu reaction by coupling of aniline, ethyl acetoacetate, and p-benzoquinone, in 1,2-dichloroethane, using montmorillonite KSF clay as catalyst (Scheme 18) [87]. The reaction was also performed using acyclic and cyclic 1,3-diketones and with aryl and alkyl amines. Among several catalysts tested in this reaction, montmorillonite KSF clay proved to be the best catalyst leading to the highest yields in a shorter reaction time. 

---