- A concise Friedl?nder/Buchwald-Hartwig approach to the total synthesis of quindoline, a bioactive natural indoloquinoline alkaloid, and toward the unnatural 10-methylquindoline
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A new approach toward the synthesis of quindoline, a recognized indoloquinoline alkaloid, is reported. The sequence comprises the synthesis of 2-(2-nitrophenyl)quinoline through an optimized Friedl?nder condensation of 2-amino benzaldehyde with 2-nitroacetophenone, followed by the selective C-3 bromination of the quinoline moiety to direct the cyclization, reduction of the nitro group and a final Buchwald-Hartwig cyclization. In addition, quindoline was also converted to the unnatural 10-methylquindoline by reaction with dimethyl carbonate under DBU promotion. It was found that the non-directed reductive cyclization of 2-(2-nitrophenyl)quinoline results in indazolo[2,3-a]quinoline, instead of yielding quindoline. DFT calculations were employed to explain this reaction outcome; this finding suggested that the result of a previously reported total synthesis of quindoline should be revised.
- Méndez, María V.,Simonetti, Sebastian O.,Kaufman, Teodoro S.,Bracca, Andrea B. J.
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p. 10803 - 10813
(2019/07/15)
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- 3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles
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Precursors of 3-pyridylnitrene and 2- and 4-pyrimidinylcarbenes all afford mixtures of 2- and 3-cyanopyrroles on flash vacuum thermolysis, but 3-cyanopyrroles are the first-formed products. 3-Quinolylnitrenes and 4-quinazolinylcarbenes similarly afford 3-cyanoindoles. 2-Pyrimidinylcarbenes rearrange to 3-pyridylnitrenes, but 4-pyrimidinylcarbenes and 4-quinazolinylcarbenes do not necessarily rearrange to the corresponding 3-pyridylnitrenes or 3-quinolylnitrenes. The ring contraction reactions are interpreted in terms of ring opening of either the nitrenes or the diazacycloheptatetraenes to nitrile ylides.
- Wentrup, Curt,Lan, Nguyen Mong,Lukosch, Adelheid,Bednarek, Pawel,Kvaskoff, David
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p. 743 - 753
(2013/06/27)
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- Synthesis of the benzo-β-carboline isoneocryptolepine: The missing indoloquinoline isomer in the alkaloid series cryptolepine, neocryptolepine and isocryptolepine
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7H-Indolo[2,3-c]quinoline has been synthesized in two steps via a new approach starting from commercially available 3-bromoquinoline and 2-bromoaniline. The new methodology consists of two consecutive palladium-catalyzed reactions: a selective Buchwald/Ha
- Hostyn, Steven,Maes, Bert U.W.,Pieters, Luc,Lemière, Guy L.F.,Mátyus, Péter,Hajós, Gy?rgy,Dommisse, Roger A.
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p. 1571 - 1577
(2007/10/03)
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