ISSN:
0947-3440
Keywords:
Pyrolysis
;
Carbazole-1,2-dicarboxylic anhydrides
;
Carbazoles, 1,2-didehydro
;
Ring expansion to phenanthridine
;
Aryne-arene cyclisation and cycloaddition
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The flash vacuum pyrolysis (900-940°C) of a series of N-R-substituted carbazole-1,2-dicarboxylic anhydrides (R = methyl, phenyl, o-tolyl, benzyl, and ethyl) leads to 1,2-didehydrocarbazoles which undergo ring expansion, cyclisation, and other reactions but which appear not to undergo ring contraction to exocyclic carbenes. Thus the N-methyl compound 4 gives phenanthridine in 27% yield, the N-phenyl compound 5 undergoes C-2′—C-1 cyclisation to indolo[3,2,1-jk]carbazole 27, and the N-o-tolyl compound 6 gives both C-6′—C-1 cyclisation and 2′-CH3—C-1 cyclisation. The N-benzyl compound 7 mainly suffers loss of the benzyl group, but a minor product, benzo[a]carbazole 33, is probably formed by an intramolecular cycloaddition. The N-ethyl compound 8 forms mainly carbazole and phenanthridine and in addition the minor C-2′—C-1 cyclisation products pyrrolo[3,2,1-jk]carbazole 44 and its 4,5-dihydro derivative 45. The formation of phenanthridine from the N-methyl anhydride 4 has been investigated by labelling of 4 with 13C at C-9a.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970920
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