Annulation with pyrrole synthesis of indoles and carbazoles

1 Annulation with pyrrole (synthesis of indoles and carbazoles) 

Condensation of enaminone 31 (R = Ph) with ethyl bromoacetate gave hexahydroindolone 32 (91 Mil 97), whereas with pyruvic acid gave the indole derivatives 33 (R1 = Me) and 34 (R1 = Me) as the major and minor products, respectively The two diastereoisomers of 33 (R = 2,3-dichlorophenyl) were separated, when 2,3-dichlorophenyl-enamine 31 was used (85JCR(S)244) whose dehydration with acetic anhydride 

4-Benzoyl-l-phenyl-5-methoxycarbonyl-2,3-dihydro-pyrrole-2,3-dione was reacted with 5/5-dimethyl-3-p-methoxyphenylamino-2-cyclohexen-l-one in boiling benzene to afford 6,6-d imethyl-1 -p-methoxyphenyl-2,4-dioxo-2,3,4,5,6,7-hexahydro-lH-indole-3-spiro-2-(3-benzoyl-5-oxo-4-phenyl-amino-2,5-dihydrofuran) in high yield. The reaction proceeded by the enamine addition to the 2-carbonyl group with ring opening, followed by double cyclization (06RJOC772). 

Functionalization of dimedone at C-2 provided derivatives suitable for constructing the pyrrole ring. Thus, tetrahydroindole 56 was obtained 

Fischer-type reaction of enhydrazine 74a with cyclohexanone in the presence of p-toluenesultonic acid afforded octahydrocarbazole 75 (R = Me), which can be oxidized with chloranil to tetrahydrocarbazole 76 (R = Me) (70CB1767). The carbazole 76 (R = H, Et) were obtained from the enamines 77 (R = H, Et) by photolysis in dioxane-acetonitrile containing triethylamine or by treatment with triphenylphosphine-palladium acetate complex (2 1) in DMF in the presence of NaHCCb 

---