A New Modular Indole Synthesis. Construction of the Highly Strained CDEF Parent Tetracycle of Nodulisporic Acids A and B

Smith, Amos B.; Kürti, László; Davulcu, Akin H.

doi:10.1021/ol0606536

Cited by 33 publications

(7 citation statements)

References 15 publications

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“…Synthesis of the requisite cyclization precursors 1-3 was accomplished through a Stille coupling reaction between an ortho-substituted arene and vinyl stannane utilizing Pd(PPh 3 ) 4 or Pd 2 dba 3 /tri(2-furyl)phosphine with excess CuI in NMP. [20] Preliminary investigation and optimization of the cyclization centered on three substrates to determine the feasibility of this methodology. In a screen of cyclization conditions, treatment of 1 with 10 mol% of (8S, 9R)-N-benzylcinchonidinium chloride 7 in toluene with either aqueous K 2 CO 3 or solid Cs 2 CO 3 returned only starting material (Table 1).…”

Section: Resultsmentioning

confidence: 99%

Catalytic enantioselective synthesis of indanes by a cation-directed 5-endo-trig cyclization

et al. 2015

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5-Endo-trig cyclizations are generally considered to be kinetically unfavourable, as described by Baldwin's rules. Consequently, observation of this mode of reaction under kinetic control is rare. This is usually ascribed to challenges in achieving appropriate approach trajectories for orbital overlap in the transition state. Here, we describe a highly enantio- and diastereoselective route to complex indanes bearing all-carbon quaternary stereogenic centres via a 5-endo-trig cyclization catalysed by a chiral ammonium salt. Through computation, the preference for the formally disfavoured 5-endo-trig Michael reaction over the formally favoured 5-exo-trig Dieckmann reaction is shown to result from thermodynamic contributions to the innate selectivity of the nucleophilic group, which outweigh the importance of the approach trajectory as embodied by Baldwin's rules. Our experimental and theoretical findings demonstrate that geometric and stereoelectronic constraints may not be decisive in the observed outcome of irreversible ring-closing reactions.

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Section: Resultsmentioning

confidence: 99%

Catalytic enantioselective synthesis of indanes by a cation-directed 5-endo-trig cyclization

et al. 2015

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“…The ester 4 was then transformed into hydrazone 5 by reacting it with N -aminoindoline in methanol. N -Aminoindoline was prepared from commercially available indoline via a nitrosation–reduction sequence . In the next step, the ester group of 5 was converted into the corresponding phosphonate by reacting it with deprotonated methyl dimethylphosphonate in THF at −78 °C .…”

Section: Resultsmentioning

confidence: 99%

3-(Hetero)aryl-4-indolylamino-α-tetralones by Diastereoselective Internal Redox Cyclization: An “Azaenamine” Conjugate Addition

et al. 2011

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(E)-3-(hetero)aryl-1-(2-((E)-(indolin-1-ylimino)methyl)phenyl)prop-2-en-1-ones 1 undergo 6-exo-trig cyclization reactions upon treatment with BF(3)·Me(2)S in dichloromethane at low temperature to give the tetralones 10 in good yield. This cyclization process can be considered to be an intramolecular Michael-type addition which is accompanied by an internal redox reaction as the indoline fragment is oxidized to indole with simultaneous hydrogen shift to nitrogen atom N1 and the α-carbon atom of the Michael system. The reactions at the iminic centers take place via umpolung of the classical carbonyl reactivity. The reaction is diastereoselective and affords exclusively 3,4-disubstituted α-tetralones 10 as trans-diastereomers. According to quantum chemical calculations the reactions take place under kinetic control with the trans-diastereomer being the kinetically favored product as it has the lower activation barrier compared to the cis-diastereomer.

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“…36 A related intramolecular amination reaction between an aniline and an alkenyl triflate was employed by Smith and co-workers in their synthesis of the nodulisporic acids tetracycle. 37 The Willis research group also demonstrated that similar palladium-catalyzed cascade processes can be achieved using pyridine-derived substrates to provide access to the corresponding azaindole products. 35e For example, reaction of dihalopyridine substrate 24 with p-anisidine, using a DPEPhos-derived catalyst, delivered the corresponding 7-azaindole in good yield (Scheme 9).…”

Section: %mentioning

confidence: 99%

Palladium- and Copper-Catalyzed Aryl Halide Amination, Etherification and Thioetherification Reactions in the Synthesis of Aromatic Heterocycles

Sadig¹,

Willis²

2010

Synthesis

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This article reviews the use of palladium-and coppercatalyzed aryl halide amination, etherification and thioetherification processes in the synthesis of heteroaromatic molecules. The review is structured by the nature of the key C-X bond being formed, and then by heterocycle type. Where applicable individual heterocycles are further divided into syntheses based on intermolecular, intramolecular and cascade processes. In order to limit the length of the article, processes that do not deliver an aromatic heterocycle from the key C-X bond-forming event are excluded. Processes for the functionalization of intact heteroaromatics are also not included.

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A New Modular Indole Synthesis. Construction of the Highly Strained CDEF Parent Tetracycle of Nodulisporic Acids A and B

Cited by 33 publications

References 15 publications

Catalytic enantioselective synthesis of indanes by a cation-directed 5-endo-trig cyclization

Catalytic enantioselective synthesis of indanes by a cation-directed 5-endo-trig cyclization

3-(Hetero)aryl-4-indolylamino-α-tetralones by Diastereoselective Internal Redox Cyclization: An “Azaenamine” Conjugate Addition

Palladium- and Copper-Catalyzed Aryl Halide Amination, Etherification and Thioetherification Reactions in the Synthesis of Aromatic Heterocycles

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