Total Synthesis of the Natural Carbazoles Murrayanine and Murrayafoline A, Based on the Regioselective Diels-Alder Addition of exo -2-Oxazolidinone Dienes (original) (raw)
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Helvetica Chimica Acta, 2007
A new total synthesis of the natural carbazole murrayanine (1) was developed by using the 4,5dimethyleneoxazolidin-2-one 12 as starting material. The latter underwent a highly regioselective Diels -Alder cycloaddition with acrylaldehyde (¼ prop-2-enal; 13) to give adduct 14 (Scheme 3). Conversion of this adduct into diarylamine derivative 9 was carried out via hydrolysis and methylation (Scheme 4). Differing from our previous synthesis, in which such a diarylamine derivative was transformed into 1 by a Pd II -stoichiometric cyclization, this new approach comprised an improved cyclization through a more efficient Pd 0 -catalyzed intramolecular diaryl coupling which was applied to 9, thus obtaining the natural carbazole 1 in a higher overall yield.
A Short Synthesis of Carbazole Alkaloids Murrayanine and Mukonine
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The short, easy and total synthesis of Murrayanine (1), Mukonine (2), carbazole alkaloids were elaborated, based on a regioselective buchwald coupling of methyl 4-bromo-3-methoxybenzoate with aniline and successive transformation into the corrsponding carbazole alkaloids by oxidative coupling followed by cyclization of the phenyl and aryl rings.
DoubleN-Arylation of Primary Amines: Carbazole Synthesis from 2,2‘-Biphenyldiols
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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.
New and efficient routes for the synthesis of murrayaquinone A and murrayanine
Tetrahedron, 2012
Three new routes were established for the synthesis of biologically active murrayaquinone A and a new method was developed for synthesis of murrayanine from the same starting material as 4-hydroxy carbazole. During the synthetic course a few novel observation were recorded, which include two one pot reaction sequences and CeN bond cleavage by sodium cyanoborohydride.
Molecules
The development of a Lewis acid-catalyzed, intramolecular ring-opening benzannulation of 5-(indolyl)2,3-dihydrofuran acetals is described. The resulting 1-hydroxycarbazole-2-carboxylates are formed in up to 90% yield in 1 h. The dihydrofuran acetals are readily accessed from the reactions of enol ethers and α-diazo-β-indolyl-β-ketoesters. To highlight the method’s synthetic utility, a formal total synthesis of murrayafoline A, a bioactive carbazole-containing natural product, was undertaken.
Synthesis of Carbazoles by Intramolecular Arylation of Diarylamide Anions
Journal of Organic Chemistry, 2009
The synthesis of a series of substituted 9H-carbazoles by the photostimulated S RN 1 substitution reaction with diarylamines as starting substrate was performed. The diarylamines were obtained by two approaches, the Pd-catalyzed reactions (Buchwald-Hartwig) or Cu-catalyzed reactions of 2-haloanilines with aryl halides, or 2-bromoiodobenzene with anilines, with moderate to very good isolated yields (45-89%).
Australian Journal of Chemistry, 1986
Reaction of 7,8-dimethoxy-1,4,5,9,13c,13d-hexahydro-2H-indolo [3′,2′:4,5] indolo [1,7,6-aji] isoquinoline (4a) and 8,9-dimethoxy- 1,2,3,5,6,10,14c,14d-octahydro-indolo[3′,2′:3,4] naphtho [2,1,8-ija] quinolizine (4b) with cyanogen bromide in the presence of potassium carbonate afforded the elimination products 7,8-dimethoxy-1,2,3,4,5,9- hexahydro [3] benzazonino [8,7,6-abc]carbazole-3-carbonitrile (5a) and 8,9-dimethoxy-2,3,4,5,6,10-hexahydro-1H-[3] benzazecino [9,8,7-abc]carbazole-4-carbonitrile (5b) in 4% and 88% yield respectively; 7- (2-bromo)ethyl-1,2-dimethoxy-4,5,6,6a,7,12-hexahydroisoquino[8,1-ab ]carbazole-6-carbonitrile (6a) was also isolated in 20% yield from the former reaction. Products of analogous structure were also obtained from (4a,b) when methyl chloroformate was used in place of cyanogen bromide. Reaction of (4b) with cyanogen bromide in the presence of water and magnesium oxide afforded the solvolysis product 14d-hydroxy-8,9-dimethoxy-2,3,4,5,6,10,14d,14d-octahyd...