107816-41-1Relevant articles and documents
Exploratory Routes to Carbazole Derivatives Prelusive to 6H-Pyridocarbazole synthesis.
Hewlins, Michael J. E.,Jackson, Anthony H.,Long, Anthony,Oliveira-Campos, Ana,Shannon, Patrick V. R.
, p. 2645 - 2696 (2007/10/02)
Synthetic approaches to 3-acyl substituted carbazoles are explored.Diels-Alder additions of 2-methyl-3-trimethylsilyloxybuta-1,3-diene (7) with crotononitrile or methyl vinyl ketone gave stereoisomeric 5-cyano (or acetyl) 1-methyl-2-trimethylsilyloxy-cyclohex-1-enes.The former were readily hydrolysed to the corresponding cyclohexanones which failed to undergo Borsche cyclisation under the conditions used.The latter were reduced and then hydrolysed to a stereoisomeric mixture of 4-(1-hydroxyethyl)-2-methyl- cyclohexanones (14).The Borsche cyclisation of (14) with phenylhydrazine was attempted under a wide variety of conditions followed by attempted dehydrogenation of the intermediate tetrahydrocarbazoles with chloranil, but loss of the hydroxyethyl side chain took place giving 1-methylcarbazole as the sole isolable carbazole.In the second approach a number of N-acyl substituted diphenylamines are synthesised by the Goldberg reaction.Those lacking a 4-substituent undergo a photo-anilide rearrangement which is accompanied by carbazole formation.Diphenylamides with a 4- substituent, after hydrolysis to the diphenylamines, undergo photochemical cyclisation to 3- carbazoles but in low yield.The Goldberg synthesis of 4-formyldiphenylamides affords substantial amounts of the 4-formyldiphenylamines after work-up.These, on reaction with palladium(II) acetate in acetic acid give a mixture of products including the required 3-formyl (or carboxyl) carbazoles.
