Tetracyclic indeno indoles

An efficient three-component domino strategy for the synthesis of multi-functionahzed tetracyclic indeno[l,2-h]indole derivatives has again been reported by Tu, li, and coworkers [62]. The domino reaction between enaminones 57 and 2,2-dihydroxyindene-l,3-dione 105 in acid anhydride generated the fused pyrazoles 106 (tetracyclic 6-5-S-6 skeleton), which involved a nucleophilic substitu-tion/cychzation/methyl migration/aromatization/esterification. On the other hand,... 

Scheme 12.41 Selective synthesis of tetracyclic indeno[l, 2-b]indoles.

Li and Tu have described an innovative three-component domino reaction for the synthesis of multifunctionalized tetracyclic indeno[l,2-h]indole derivatives (Scheme 6.30) [59]. Ninhydrin 205 was used to test the allyUc esterification, but the desired product 208 was not observed during this process. Indeed, a novel polysubstituted tetracyclic indeno[l,2-fc]indole derivative 207 was obtained. Li and Tu tested then the best conditions and found out that the reaction proceeds nicely in acetic anhydride under microwave conditions in 20-32min with 63-87% yield (Scheme 6.30a). Electron-withdrawing substituents like fluoro, chloro, and bromo in the para-position of the benzene ring as well as electron-donating substituents (Me, OMe) are well tolerated in this reaction. Bulky residues do not cause any problems. 

SCHEME 6.30 Synthesis of multifunctionalized tetracyclic indeno[l,2-fc]indole derivatives 207 and 209. 

---

See also in sourсe #XX -- [ , ]

---