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Synthesis of Substituted Pyrrolo[3,4‐ a ]carbazoles
Author(s) -
Bleile Michaela,
Wagner Trixie,
Otto HansHartwig
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590231
Subject(s) - chemistry , trimethylsilyl , indole test , succinimide , stereochemistry , carbazole , cycloaddition , moiety , pyrrole , indolizine , medicinal chemistry , isatin , organic chemistry , catalysis
The cycloaddition between N ‐protected 3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1 H ‐indoles and substituted maleimides (= 1 H ‐pyrrole‐2,5‐diones) yielded substituted pyrrolo[3,4‐ a ]carbazole derivatives bearing an additional succinimide (= pyrrolidine‐2,5‐dione) moiety either at C(5a) or C(10b) depending on the type of the protection group at the indole N‐atom. Derivatives substituted at C(10b) were isolated when the protection group, Me 3 Si or Boc ( t BuOCO), was eliminated during the reaction ( Schemes 2 and 3 ), whereas a substitution at C(5a) was observed when an electron‐withdrawing group, Tos (4‐MeC 6 H 4 SO 2 ) or pivaloyl (Me 3 CCO), was not eliminated ( Scheme 1 ). Complex results were found in reactions between 1‐(trimethylsilyl)‐3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1 H ‐indole, in contrast to formerly reported results ( Scheme 3 ). Some derivatives of 1 H ,5 H ‐[1,2,4]triazolo[1′,2 : 1,2]pyridazino[3,4‐ b ]indole‐1,3(2 H )‐dione were obtained from reactions with 4‐phenyl‐3 H ‐1,2,4‐triazole‐3,5(4 H )‐dione ( Scheme 2 ). All structures were established by spectroscopic data, by calculations, and one representative structure was confirmed by an X‐ray crystallographic analysis ( Fig. ). Finally, the formation of the different structure types was discussed, and compared with similar reactions reported in the literature.