Studies in the Indole Series. II. A General Synthesis of Cycloalkan[b]indolones

Intramolecular Ritter Reactions of 2‐(2‐Cyanoethyl)tetrahydrocyclopenta[b]indole and ‐carbazole Derivatives

“…The starting five-membered ring ketone 12 [4-methyl-1,4-dihydrocyclopenta [b]indol-3(2H)-one] was prepared by Nmethylation of 3-indolepropionic acid (10), [9,10] followed by acid-catalysed cyclisation of 3-(1-methyl-1H-indol-3-yl)propanoic acid (11). [11] Subsequent methoxycarbonylation of the electron-rich ketone 12 with dimethyl carbonate required use of a stronger base (KH) than that applied for the analogous conversion of 1-indanone (NaH).…”

“…[11] Subsequent methoxycarbonylation of the electron-rich ketone 12 with dimethyl carbonate required use of a stronger base (KH) than that applied for the analogous conversion of 1-indanone (NaH). [1] Final Michael addition of β-keto ester 13 to acrylonitrile in tBuOH as a solvent and with tBuOK as a base catalyst afforded the required keto nitrile precursor 14 (Scheme 2).…”

“…In this case Nmethylation was carried out on the intermediate six-membered ketone 17, [11] which could easily be isolated by column chromatography, in contrast to the more polar N-unmethylated analogue of the five-membered ring ketone 12.…”

Incorporation of an indole-containing diarylbutylamine pharmacophore into furo[2,3-a]carbazole ring systems

“…An acidcatalysed ring closure of 3-indolebutyric acid afforded the six-membered ring ketone 8, 6 which was N-methylated to give compound 9. 7,8 b-Keto ester 10 was prepared by treatment of 9 with potassium hydride and dimethyl carbonate.…”

Synthesis of Cycloalk[b]indole Bearing Spiropiperidine Derivatives

“…The synthesis of spiropiperidinone and spiropiperidinedione structures was performed by a new method [13][14][15]. For this aim, we used easily available compounds 1a-c and 6a-c as starting compounds and synthesized according to the literature [16][17][18][19][20]. The β-ketoesters (2a, 2b, 2c, 7a [20], 7b [21], and 7c) were prepared with the condensation reaction between keto compounds (1a-c and 6a-c) and diethyl carbonate in the presence of potassium hydride [21,22].…”