Eight-Membered Ring Formation via Olefin Insertion into a Carbon—Carbon Single Bond.

The reaction of α,ω-dihalides with the dianion of methyl acetoacetate gives a mixture of mono- and bisalkylated products. The monoalkylated products can be cyclized via the monoanion to cyclic β-keto esters with a seven- or eight-membered ring. Alternatively these monoalkylated products can be cyclized via the dianion to γ-cyclopentyl- or γ-cyclohexyl-β-keto esters.

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Synthesis, crystal structure and molecular conformation of (±)-1-oxoferruginol and (±)-shonanol

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.219.10.659.50814 ◽

2004 ◽

Vol 219 (10) ◽

Author(s):

Swastik Mondal ◽

Monika Mukherjee ◽

Arnab Roy ◽

Debabrata Mukherjee

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Diffraction Data ◽

Molecular Conformation ◽

Membered Ring ◽

Methyl Groups ◽

Single Bond ◽

X Ray Diffraction ◽

X Ray ◽

Chemical Structures

Abstract(±)-1-oxoferruginol and (±)-shonanol, two potential intermediates in the synthesis of tricyclic diterpenoid ferruginol, have been prepared and crystal structures of the compounds have been investigated using single-crystal X-ray diffraction data. The methyl groups of the isopropyl moiety in (±)-shonanol are disordered over two positions with occupation factors 0.65(1) and 0.35(1), respectively. Although the chemical structures of two compounds are very similar, a C—C single bond in the terminal six-membered ring of (±)-1-oxoferruginol is replaced by a C=C bond in (±)-shonanol, the quantitative isostructurality index calculations indicate that the structures are not isostructural. Intermolecular O—H…O hydrogen bonds between pairs of molecules in the compounds related by center of inversion lead to characteristic dimers forming R

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Seven-Membered Ring Formation through a Robinson Annulation

Category 6, Compounds with All-Carbon Functions ◽

10.1055/sos-sd-045-01169 ◽

2010 ◽

pp. 1

Author(s):

K. Abou-Hadeed ◽

H.-J. Hansen

Keyword(s):

Membered Ring ◽

Ring Formation ◽

Robinson Annulation

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Annulation of Indoles with 1,n-Dibromoalkanes by a Pd(II)-Catalyzed and Norbornene-Mediated Reaction Cascade

Synthesis ◽

10.1055/s-0039-1690693 ◽

2019 ◽

Vol 52 (08) ◽

pp. 1231-1238 ◽

Cited By ~ 2

Author(s):

Michael Henkel ◽

Thorsten Bach

Keyword(s):

Direct Synthesis ◽

Membered Ring ◽

Ring Formation ◽

Cascade Process

Employing 1,3-dibromopropane, 1,4-dibromobutane, and 1,5-dibromopentane as biselectrophiles, the annulation of indoles was probed in the presence of PdCl2(MeCN)2 as a catalyst and norbornene as a transpositional ligand. Ring formation to a five-membered ring was observed at positions C2 and N, while annulation of a six-membered ring occurred at positions C2 and C3. The latter cascade process was successfully applied to the direct synthesis of 1,2,3,4-tetrahydrocarbazoles from indoles (11 examples, 31–68% yield). Seven-membered-ring annulation was feasible by an initial coupling at positon C2 followed by alkylation at C3.

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