- Pd-Catalyzed Formal [3 + 3] Heteroannulation of Allylic gem-Diacetates: Synthesis of Chromene-Based Natural Products and Exploration of Photochromic Properties
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Palladium-catalyzed allylic alkylation reactions of allylic gem-diacetates are rarely explored. This work unveils an unusual chemical reactivity pattern of allylic gem-diacetates and establishes them as new prototypes to synthesize complex benzo[f]chromene systems. Under the reaction conditions, the diacetates behave as 1,3-dicationic equivalents and undergo a [3 + 3] heteroannulation with 2-naphthols (and meta-substituted phenols) to produce novel polycyclic chromenes possessing spiro-, tri-, and tetrasubstituted carbon centers. The versatility of the method is demonstrated in the synthesis of several chromene-based bioactive natural products. Further, interesting photochromic properties of the new classes of benzo[f]chromenes are also discovered.
- Kumar, Prashant,Kumar, Pravesh,Venkataramani, Sugumar,Ramasastry
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p. 963 - 970
(2022/01/19)
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- Preparation method of pyran[3,2-a]carbazole compound
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The invention relates to a preparation method of a pyran[3,2-a]carbazole compound represented by the formula (I). The preparation method comprises following steps: step one, taking 5-nitro-phenol as raw material to synthesize 3-(3'-3'-dimethylbutyne ether)-nitrobenzene; step two, preparing pyran[3,2-a]nitrobenzene from 3-(3'-3'-dimethylbutyne ether)-nitrobenzene through 3,3-sigma migration reactions between terminal alkyne hydrogen and a benzene ring system; step three, reducing pyran[3,2-a]nitrobenzene to obtain pyran[3,2-a]aniline; step four, preparing pyran[3,2-a]diphenylamine from pyran[3,2-a]aniline and aryl halide; and step five, preparing the pyran[3,2-a]carbazole compound from pyran[3,2-a]diphenylamine. The provided preparation method has the advantages that the steps of the synthesis route are few, the reaction conditions are mild, the adverse reactions are effectively reduced, the substrate universality is good, and the yield of target compound is high.
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- Pyrano[3,2-a]carbazole alkaloids as effective agents against ischemic stroke in vitro and in vivo
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A series of pyrano[3,2-a]carbazole alkaloids were designed and synthesized as analogues of Claulansine F (Clau F, 10a) isolated from Clausena lansium. Some of compounds showed strong neuroprotective effects and were promising agents against ischemic stroke. Among these compounds, 7c was the most active in inhibiting the programmed death of PC12 cells and primary cortical neurons. This compound induced neuroprotection following ischemic reperfusion and decreased neurological deficit scores in treated animals. Furthermore, 7c could penetrate the blood-brain barrier (BBB) in rats, and its exposure in the brain was 4.3-fold higher than that in plasma. More importantly, compared to edaravone, 7c exhibited stronger free radical scavenging activity. Our findings suggest that 7c may be promising for further evaluation as an intervention for ischemic stroke.
- Zang, Yingda,Song, Xiuyun,Li, Chuangjun,Ma, Jie,Chu, Shifeng,Liu, Dandan,Ren, Qian,Li, Yan,Chen, Naihong,Zhang, Dongming
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p. 438 - 448
(2017/12/07)
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- "on Water" Promoted Ullmann-Type C-N Bond-Forming Reactions: Application to Carbazole Alkaloids by Selective N-Arylation of Aminophenols
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The Ullmann-type cross coupling of a variety of aromatic, aliphatic amines with aryl halides is reported using a CuI-based catalytic system in combination with an easily accessible prolinamide ligand in aqueous media. The method is mild and tolerant to air, moisture, and a wide range of functional groups, providing a novel way to access a variety of aminated products. Secondary amines like heteroaromatic amines and nucleobases have also been used, affording the corresponding coupling products in good to excellent yields. Moreover, this method has been employed for chemoselective C-N arylation of aminophenols and further utilized for the synthesis of carbazole natural products, avoiding the protection and deprotection steps.
- Chakraborti, Gargi,Paladhi, Sushovan,Mandal, Tirtha,Dash, Jyotirmayee
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p. 7347 - 7359
(2018/07/29)
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- Divergent and Orthogonal Approach to Carbazoles and Pyridoindoles from Oxindoles via Indole Intermediates
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The previously unexplored Grignard addition to oxindoles provides a regiospecific approach to 2- and 2,3-disubstituted indole derivatives in high yields via a one-pot aromatization driven dehydration pathway. This method allows a convenient preparation of diallyl indoles that are used as ring-closing metathesis (RCM) precursors for the orthogonal synthesis of pyrido[1,2-a]indoles and carbazoles. The synthetic utility of this method is illustrated by the synthesis of a microtubulin inhibitor and naturally occurring carbazole alkaloids.
- Mandal, Tirtha,Chakraborti, Gargi,Karmakar, Shilpi,Dash, Jyotirmayee
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p. 4759 - 4763
(2018/08/24)
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- Total synthesis of the biscarbazole alkaloids murrafolinea a-d by a domino sonogashira coupling/claisen rearrangement/electrocyclization reaction
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Why take things one step at a time? Aryl-pyran-linked biscarbazole alkaloids of the murrafoline group (see crystal structure of murrafolinea A; dark gray: C, red: O, blue: N) were accessed readily by a novel domino reaction sequence involving Sonogashira
- Kumar, V. Pavan,Gruner, Konstanze K.,Kataeva, Olga,Knoelker, Hans-Joachim
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p. 11073 - 11077
(2013/10/22)
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- Efficient construction of pyrano [3, 2-a]carbazoles: Application to a biomimetic total synthesis of cyclized monoterpenoid pyrano [3, 2-a]carbazole Alkaloids
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We have developed a highly efficient route to 2-hydroxy-3-methyl-carbazole (1) via a palladium-catalyzed construction of the carbazole skeleton. Using 1 as relay compound, different methods for annulations of pyran rings by reaction with terpenoid building blocks have been tested. The Lewis acid promoted reaction of 1 with prenal (21) opened up an efficient route to girinimbine (3) and the corresponding reaction with citral (25) afforded mahanimbine (5). Oxidation of compounds 3 and 5 provided murraya-cine (4) and murrayacinine (6). Following the biogenetic proposal, mahanim-bine (5) has been exploited for efficient biomimetic syntheses of the cyclized monoterpenoid pyrano[3, 2-a]carbazole alkaloids cyclomahanimbine (7), maha-nimbidine (8) and bicyclomahanimbine (9). The interconversions of 5, 7, 8 and 9 are described and mechanistic implications are discussed. Structural assignments are unambiguously verified by X-ray crystal structure determinations. Moreover, cyclomahanimbine (7) was transformed into murrayazolinine (10) and exozoline (11).
- Hesse, Ronny,Gruner, Konstanze K.,Kataeva, Olga,Schmidt, Arndt W.,Kn?lker, Hans-Joachim
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p. 14098 - 14111
(2013/11/06)
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- Efficient iron-mediated approach to pyrano[3,2-a]carbazole alkaloids - First total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine, first asymmetric synthesis and assignment of the absolute configuration of (-)-trans-dihydroxygirinimbine
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Iron-mediated oxidative cyclisation provides an efficient approach to pyrano[3,2-a]carbazole alkaloids. Thus, improved routes to girinimbine and murrayacine as well as the first total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine are reporte
- Gruner, Konstanze K.,Hopfmann, Thomas,Matsumoto, Kazuhiro,Jaeger, Anne,Katsuki, Tsutomu,Knoelker, Hans-Joachim
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scheme or table
p. 2057 - 2061
(2011/05/14)
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- Palladium-catalyzed total synthesis of euchrestifoline using a one-pot Wacker oxidation and double aromatic C-H bond activation
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We describe the total synthesis of euchrestifoline featuring an unprecedented one-pot Wacker oxidation and double aromatic C-H bond activation. The 2008 Royal Society of Chemistry.
- Gruner, Konstanze K.,Knoelker, Hans-Joachim
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scheme or table
p. 3902 - 3904
(2009/06/28)
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- Transition metal complexes in organic synthesis. Part 33. Molybdenum-mediated total synthesis of girinimbine, murrayacine, and dihydroxygirinimbine
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A highly convergent total synthesis of the pyrano[3,2-a]carbazole alkaloids girinimbine, murrayacine, and dihydroxygirinimbine has been accomplished using a consecutive molybdenum-mediated C-C- and C-N-bond formation.
- Knoelker, Hans-Joachim,Hofmann, Christoph
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p. 7947 - 7950
(2007/10/03)
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- A New Synthesis of Girinimbine
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The synthesis of girinimbine (I), a pyranocarbazole involves reaction of 2-hydroxy-3-methylcarbazole (II) with 3-chloro-3-methyl-1-butyne in the presence of AlCl3.
- Bhattacharyya, P.,Chakraborty, A.
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