Six- versus Five-Membered Ring Formation in Radical Cyclizations of 7-Bromo-Substituted Hexahydroindolinones

2004 ◽  
Vol 6 (6) ◽  
pp. 917-920 ◽  
Author(s):  
Paitoon Rashatasakhon ◽  
Ayse Daut Ozdemir ◽  
Jerremey Willis ◽  
Albert Padwa
Keyword(s):  
Membered Ring ◽  
Ring Formation ◽  
Radical Cyclizations

scholarly journals Mimicking Noncanonical Oxidations with Redox-Neutral Photocatalysis

2019 ◽  
Author(s):  
Zheng Huang ◽  
Jean-Philip Lumb
Keyword(s):  
Organic Synthesis ◽  
Structural Features ◽  
Membered Ring ◽  
Ring Formation ◽  
Radical Cyclizations ◽  
General Strategy ◽  
Sufficient Time ◽  
Lignan Biosynthesis

Noncanonical oxygenases are a family of Fe-containing enzymes that catalyze oxidative radical cyclizations. Despite creating key structural features that often define a natural product’s complexity, the mechanisms of these oxidations remain poorly understood and difficult to mimic. In this work, we show that noncanonical cyclizations from lignan biosynthesis can be recreated when presumed biosynthetic radicals are generated using photocatalysis. These conditions afford the ensuing electron rich radicals sufficient time to undergo challenging 5- or 11-membered ring formation that create the defining structural features of the highly oxidized lignans taiwankadsurins A, B and kadsuphilin N. By showing that these cyclizations can occur without enzymatic assistance, we provide a more general strategy for mimicking noncanonical transformations that should broaden their use in organic synthesis.

scholarly journals Mimicking Noncanonical Oxidations with Redox-Neutral Photocatalysis

2019 ◽  
Author(s):  
Zheng Huang ◽  
Jean-Philip Lumb
Keyword(s):  
Organic Synthesis ◽  
Structural Features ◽  
Membered Ring ◽  
Ring Formation ◽  
Radical Cyclizations ◽  
General Strategy ◽  
Sufficient Time ◽  
Lignan Biosynthesis

Noncanonical oxygenases are a family of Fe-containing enzymes that catalyze oxidative radical cyclizations. Despite creating key structural features that often define a natural product’s complexity, the mechanisms of these oxidations remain poorly understood and difficult to mimic. In this work, we show that noncanonical cyclizations from lignan biosynthesis can be recreated when presumed biosynthetic radicals are generated using photocatalysis. These conditions afford the ensuing electron rich radicals sufficient time to undergo challenging 5- or 11-membered ring formation that create the defining structural features of the highly oxidized lignans taiwankadsurins A, B and kadsuphilin N. By showing that these cyclizations can occur without enzymatic assistance, we provide a more general strategy for mimicking noncanonical transformations that should broaden their use in organic synthesis.

scholarly journals Six- versus Five-Membered Ring Formation in Radical Cyclizations of 7-Bromo-Substituted Hexahydroindolinones.

ChemInform ◽  
2004 ◽  
Vol 35 (31) ◽  
Author(s):  
Paitoon Rashatasakhon ◽  
Ayse Daut Ozdemir ◽  
Jerremey Willis ◽  
Albert Padwa
Keyword(s):  
Membered Ring ◽  
Ring Formation ◽  
Radical Cyclizations

Ring formation via β-keto ester dianions

1977 ◽  
Vol 55 (6) ◽  
pp. 996-1000 ◽  
Author(s):  
Phaik-Eng Sum ◽  
Larry Weiler
Keyword(s):  
Membered Ring ◽  
Ring Formation ◽  
Methyl Acetoacetate ◽  
Keto Ester ◽  
Keto Esters

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.

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

Synthesis ◽  
2019 ◽  
Vol 52 (08) ◽  
pp. 1231-1238 ◽  
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.

ChemInform Abstract: Six-Membered Ring Formation with o-Phenylene-diphosphine.

ChemInform ◽  
1987 ◽  
Vol 18 (22) ◽  
Author(s):  
K. ISSLEIB ◽  
E. LEISSRING ◽  
H. SCHMIDT
Keyword(s):  
Membered Ring ◽  
Ring Formation

scholarly journals On-Surface Synthesis of Indenofluorene Polymers by Oxidative Five-Membered Ring Formation

2018 ◽  
Vol 140 (10) ◽  
pp. 3532-3536 ◽  
Author(s):  
Marco Di Giovannantonio ◽  
José I. Urgel ◽  
Uliana Beser ◽  
Aliaksandr V. Yakutovich ◽  
Jan Wilhelm ◽  
...  
Keyword(s):  
Membered Ring ◽  
Ring Formation

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

ChemInform ◽  
2004 ◽  
Vol 35 (47) ◽  
Author(s):  
Takanori Matsuda ◽  
Atsushi Fujimoto ◽  
Mitsuru Ishibashi ◽  
Masahiro Murakami
Keyword(s):  
Membered Ring ◽  
Ring Formation ◽  
Single Bond
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