✍ Scribed by Richard A. Bunce; Baskar Nammalwar
No coin nor oath required. For personal study only.
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Efficient syntheses of the title ring systems have been developed from 1__H__‐indole‐2‐butanoic acid, which was easily prepared from 2‐fluoro‐1‐nitrobenzene in four steps. Heating 1__H__‐indole‐2‐butanoic acid in toluene containing p‐toluenesulfonic acid at 110°C furnished 1,2,3,9‐tetrahydro‐4__H__‐carbazol‐4‐one in 88% yield. Heating this same acid in toluene with no added acid gave 8,9‐dihydropyrido[1,2‐a]indol‐6(7__H__)‐one in 90% yield. The tetrahydro‐4__H__‐carbazol‐4‐one was also prepared directly in 92% yield from methyl 6‐(2‐nitrophenyl)‐5‐oxohexanoate by a tandem reduction—cycloaromatization—acylation reaction with iron in concentrated hydrochloric acid at 110°C. Application of this approach to the closure of five‐ and seven‐membered rings was also successful. J. Heterocyclic Chem., (2009).
📜 SIMILAR VOLUMES
Eingegangen am 31. Oktober 1986 Pyrano[ 3,4-blindolones 3a-d are available from a-ethoxyalyllactones la, c and disubstituted hydrazines 2a, b without isolation of intermediates. In a two-phase system, however, the intermediate hydrazones 4a, c can be isolated. Conversion of 3a-d into P-carbolines wa