Double N-arylation of primary amines: carbazole synthesis from 2,2'-biphenyldiols.
The double N-arylation of primary amines with 2,2'-biphenylylene ditriflates was investigated for the synthesis of multisubstituted carbazoles. Palladium complexes supported by 2-dicyclohexylphosphino-2'-methylbiphenyl or Xantphos [4,5-bis(diphenylphosphino)-9,9-dimethylxanthene] were found to be efficient catalysts for the reaction. The catalysts allow the use of anilines with an electron-donating or electron-withdrawing substituent and multisubstituted 2,2'-biphenylylene ditriflates as substrates. Ammonia equivalents, such as O-tert-butyl carbamate, are also employable as a nitrogen source to give the N-protected carbazoles which can easily give the corresponding N-unsubstituted carbazoles after deprotection. By using this methodology, a carbazole alkaloid, mukonine, is synthesized in 40% yield for five steps, in comparable efficiency to the recent precedents.
Kuwahara
Atsushi
A
Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Nakano
Koji
K
Nozaki
Kyoko
K
D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D002227:Carbazoles / Q000138:chemical synthesis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D003500:Cyclization; D008024:Ligands; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*
D000470:Alkaloids; D000588:Amines; D002227:Carbazoles; D008024:Ligands; D010636:Phenols; C038764:2,2'-biphenol