Palladium-catalyzed syntheses of tetrahydrocarbazolones as advanced intermediates to carbazole alkaloids

Scott, Tricia L.; Yu, Xue; Gorugantula, Sobha P.; Carrero‐Martinez, Grissell; Söderberg, Björn C.G.

doi:10.1016/j.tet.2006.08.100

Cited by 38 publications

(15 citation statements)

References 28 publications

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“…The palladium‐catalyzed reductive cyclization of nitrostyrenes was also employed to synthesize several tetrahydrocarbazolones, which can be employed as advanced intermediates in the synthesis of carbazole alkaloids such as clausenalene (Scheme ) …”

Section: Synthesis Of N‐heterocycles By Intra‐molecular Cyclization Rmentioning

confidence: 99%

“…The palladium-catalyzed reductive cyclization of nitrostyrenes was also employed to synthesize several tetrahydrocarbazolones, which can be employed as advanced intermediates in the synthesis of carbazole alkaloids such as clausenalene (Scheme 24). [121] The cyclization of an o-nitrostyrene was also employed as a step in the synthesis of salviadione (Scheme 25). [122] Attempted cyclization of the quinole (lower reaction in the scheme) resulted in the complete consumption of the reagent, but only gave small amounts of the desired dione, accompanied by a complex mixture of compounds.…”

Section: Synthesis Of Indolesmentioning

confidence: 99%

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Transition Metal Catalyzed Reductive Cyclization Reactions of Nitroarenes and Nitroalkenes

2019

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Nitroarenes are the entry point for the production of most nitrogen‐containing aromatic compounds. Thus, any transformation that leads directly from them to the final product allows saving one or more synthetic steps. This review deals with homogeneously catalyzed reactions leading to the formation of N‐heterocyclic compounds from nitroarenes or nitroalkenes in one pot. Reactions that lead to the intermediate formation of amines are not considered. Carbon monoxide is the most often employed reductant because it allows selective reactions, is cheap, and only produces CO2 as stoichiometric byproduct. However, the difficulty in handling pressurized CO has stimulated in recent years the development of CO‐surrogates, that is molecules able to liberate CO during the reaction. The use of phosphines and diols has also been developed in conjunction with molybdenum catalysts. The review focusses in more detail on the literature in the period 2006–2018, but reference to earlier work is made when necessary to put recent results in a more general context.

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Section: Synthesis Of N‐heterocycles By Intra‐molecular Cyclization Rmentioning

confidence: 99%

Section: Synthesis Of Indolesmentioning

confidence: 99%

Transition Metal Catalyzed Reductive Cyclization Reactions of Nitroarenes and Nitroalkenes

2019

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“…For naturally occurring carbazole alkaloids see: Scott et al (2006). For the biological activity of carbazole alkaloids see: Ramsewak et al(1999); Tachibana et al (2001); Nakahara et al (2002).…”

Section: Related Literaturementioning

confidence: 99%

2-(2,3,4,9-Tetrahydro-1H-carbazol-1-ylidene)propanedinitrile

Archana¹,

Prabakaran²,

Prasad³

et al. 2010

Acta Cryst E

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In the title molecule, C15H11N3, the dihedral angle between the benzene ring and the fused pyrrole ring is 1.07 (5)°. The cyclohexene ring adopts an envelope conformation: the dicyanomethylene group at position 1 has a coplanar orientation. An intramolecular N—H⋯N hydrogen bond generates an S(7) ring motif. Intermolecular N—H⋯N hydrogen bonds form an R 2 2(14) ring in the crystal. A C—H⋯π interaction involving the benzene ring is also found in the structure.

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“…Söderberg's method has been successfully applied to the synthesis of a number of indole analogs including tryptophan derivatives, 14 bicyclic heteroaromatics, 15 carbazole alkaloids, 16 mushroom metabolites, 17 and various natural products. [18][19][20][21][22][23][24][25] Through a detailed optimization study of the reaction conditions, it was observed that the Pd(dba)2-dppp-1,10-phenanthroline system using DMF as solvent at 120 °C under 6 atm of carbon monoxide (Scheme 3) was highly applicable to late stage indolization during many natural products syntheses. [22][23][24][25] Scheme 3: Söderberg Reductive N-Heterocyclization Optimized for Late Stage Indolization in Natural Products Synthesis…”

Section: Scheme 2: Watanabe and Söderberg Reductive Heterocyclizationmentioning

confidence: 99%

Syntheses of azepinoindole alkaloids cimitrypazepine, fargesine and hyrtioreticulins C & D

Ghimire¹

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Syntheses of azepinoindole alkaloids cimitrypazepine, fargesine and hyrtioreticulins C & D Ganesh Ghimire The Watanabe-Cenini-Söderberg reductive N-heterocyclization has emerged as a powerful tool for the synthesis of a variety of functionalized indoles. Söderberg's elaboration of this methodology has been utilized as a late-stage cyclization protocol for the synthesis of azepinoindole alkaloids, a class of natural products characterized by an azepane skeleton fused with an indole ring. Short syntheses of the naturally occurring azepino[5,4,3-cd]indole alkaloids, cimitrypazepine, fargesine, and the diastereomeric hyrtioreticulins C & D have been completed starting from commercially available tetra-substituted benzene derivatives. The key azepinoindole core in each case was assembled via an intramolecular Mizoroki-Heck reaction followed by a Watanabe-Cenini-Söderberg reductive N-heterocyclization. Synthesis of aurantioclavine using a similar strategy is currently underway.

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Palladium-catalyzed syntheses of tetrahydrocarbazolones as advanced intermediates to carbazole alkaloids

Cited by 38 publications

References 28 publications

Transition Metal Catalyzed Reductive Cyclization Reactions of Nitroarenes and Nitroalkenes

Transition Metal Catalyzed Reductive Cyclization Reactions of Nitroarenes and Nitroalkenes

2-(2,3,4,9-Tetrahydro-1H-carbazol-1-ylidene)propanedinitrile

Syntheses of azepinoindole alkaloids cimitrypazepine, fargesine and hyrtioreticulins C & D

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