Cyclopentanoids by Uncatalyzed Intramolecular Carbonyl Ene (ICE) Reaction of α-Keto Esters

Tymann, David; Klüppel, André; Hiller, Wolf; Hiersemann, Martin

doi:10.1021/ol501204m

Cited by 13 publications

(5 citation statements)

References 32 publications

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“…[21] Furthermore,w ef ound that, in the presence of TiCl 4 ,t he external olefin moiety in indoline 15,o btainedi nt wo-step reactions, reduction of the aldehydet oan alcohol followed by acylation, could undergo isomerizationt og ive aromatic indole 16 in ah igh yield (Scheme6). Finally,a ni ntramolecular carbonylene reaction [22] of 5b through treatment with TiCl 4 gave rise to cyclopent [b]indole 17 in excellent yield. Compound 17 is an important precursor fort he synthesis of natural product bruceollineD (19).…”

Section: Synthetic Applicationsmentioning

confidence: 99%

Facile Installation of 2‐Reverse Prenyl Functionality into Indoles by a Tandem N‐Alkylation–Aza‐Cope Rearrangement Reaction and Its Application in Synthesis

Chen

Fan

Zhang

et al. 2015

Chemistry A European J

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An unprecedented tandem N-alkylation-ionic aza-Cope (or Claisen) rearrangement-hydrolysis reaction of readily available indolyl bromides with enamines is described. Due to the complicated nature of the two processes, an operationally simple N-alkylation and subsequent microwave-irradiated ionic aza-Cope rearrangement-hydrolysis process has been uncovered. The tandem reaction serves as a powerful approach to the preparation of synthetically and biologically important, but challenging, 2-reverse quaternary-centered prenylated indoles with high efficiency. Notably, unusual nonaromatic 3-methylene-2,3-dihydro-1H-indole architectures, instead of aromatic indoles, are produced. Furthermore, the aza-Cope rearrangement reaction proceeds highly regioselectively to give the quaternary-centered reverse prenyl functionality, which often produces a mixture of two regioisomers by reported methods. The synthetic value of the resulting nonaromatic 3-methylene-2,3-dihydro-1H-indole architectures has been demonstrated as versatile building blocks in the efficient synthesis of structurally diverse 2-reverse prenylated indoles, such as indolines, indole-fused sultams and lactams, and the natural product bruceolline D.

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Section: Synthetic Applicationsmentioning

confidence: 99%

Facile Installation of 2‐Reverse Prenyl Functionality into Indoles by a Tandem N‐Alkylation–Aza‐Cope Rearrangement Reaction and Its Application in Synthesis

Chen

Fan

Zhang

et al. 2015

Chemistry A European J

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“…For the synthesis of terpenoid-related building blocks, in particular cyclopentanoids, see: Becker et al (2013); Gille et al (2011); Helmboldt et al (2006); Nelson et al (2011); Tymann et al(2014). For a review on cyclopentanoids by ring contraction see: Silva (2002).…”

Section: Related Literaturementioning

confidence: 99%

Crystal structure of (E)-N′-{[(1R,3R)-3-isopropyl-1-methyl-2-oxocyclopentyl]methylidene}-4-methylbenzenesulfonohydrazide

Tymann¹,

Dragon²,

Golz³

et al. 2015

Acta Cryst E

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The title compound, C17H24N2O3S, was synthesized in order to determine the relative configuration of the corresponding β-keto aldehyde. In the U-shaped molecule, the five-membered ring approximates an envelope with the methylene atom adjacent to the quaternary C atom being the flap. The dihedral angles between the four nearly coplanar atoms of the five-membered ring and the flap and the aromatic ring are 38.8 (4) and 22.9 (2)°, respectively. The bond angles around the S atom are in the range 104.11 (16)–119.95 (16)°. In the crystal, molecules are linked via N—H⋯O by hydrogen bonds, forming a chain along the a-axis direction.

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“…For the synthesis of terpenoid-related buildings blocks, in particular cyclopentanoids, see: Helmboldt et al (2006); Gille et al (2011); Becker et al (2013); Tymann et al (2014). For the crystal structure of the corresponding trans-diastereomer, see: Tymann et al (2015).…”

Section: Related Literaturementioning

confidence: 99%

Crystal structure ofN′-[(E)-(1S,3R)-(3-isopropyl-1-methyl-2-oxocyclopentyl)methylidene]-4-methylbenzenesulfonohydrazide

et al. 2015

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The title compound, C17H24N2O3S, was synthesized in order to determine the relative configuration of the corresponding β-keto aldehyde. In the U-shaped molecule, the five-membered ring approximates an envelope, with the methylene C atom adjacent to the quaternary C atom being the flap, and the methyl and isopropyl substituents lying to the same side of the ring. The dihedral angles between the four nearly coplanar atoms of the five-membered ring and the flap and the aromatic ring are 35.74 (15) and 55.72 (9)°, respectively. The bond angles around the S atom are in the range from 103.26 (12) to 120.65 (14)°. In the crystal, molecules are linked via N—H⋯O hydrogen bonds, forming a chain along the a axis.

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Cyclopentanoids by Uncatalyzed Intramolecular Carbonyl Ene (ICE) Reaction of α-Keto Esters

Cited by 13 publications

References 32 publications

Facile Installation of 2‐Reverse Prenyl Functionality into Indoles by a Tandem N‐Alkylation–Aza‐Cope Rearrangement Reaction and Its Application in Synthesis

Facile Installation of 2‐Reverse Prenyl Functionality into Indoles by a Tandem N‐Alkylation–Aza‐Cope Rearrangement Reaction and Its Application in Synthesis

Crystal structure of (E)-N′-{[(1R,3R)-3-isopropyl-1-methyl-2-oxocyclopentyl]methylidene}-4-methylbenzenesulfonohydrazide

Crystal structure ofN′-[(E)-(1S,3R)-(3-isopropyl-1-methyl-2-oxocyclopentyl)methylidene]-4-methylbenzenesulfonohydrazide

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