ChemInform Abstract: Six-Membered Ring Opening of Isopropylidene Malonate Derivatives: Synthesis of α,β-Unsaturated Thio- and Selenoaryl Carboxylic Esters.

ChemInform ◽  
2010 ◽  
Vol 26 (25) ◽  
pp. no-no
Author(s):  
W. BAO ◽  
Y. ZHANG
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Isopropylidene Malonate ◽  
Carboxylic Esters

Delineating the possibilities for intramolecular interception of the squarate ester cascade through the use of metalated enecarbamates

2000 ◽  
Vol 78 (6) ◽  
pp. 689-696 ◽  
Author(s):  
Jinsung Tae ◽  
Leo A Paquette
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Sequential Treatment ◽  
Nucleophilic Attack ◽  
Ring Strain ◽  
Multistep Process

Highly functionalized and annulated 2,4-cyclooctadienones are formed in a stereoselective manner by sequential treatment of squarate esters with a lithiated enecarbamate (six-membered ring or larger) and a cycloalkenyl- or 1-alkenyllithium reagent. The mechanistic details of this multistep process are presented. Particular attention is drawn to the step that involves intramolecular nucleophilic attack by a proximal oxido anion at the carbamate carbonyl and results in redirection of the cascade. This step is thwarted when five-membered cyclic enecarbamates are employed because of the excessive buildup of ring strain in the associated transition state.Key words: squarate esters, enecarbamates, conrotatory ring opening, intramolecular acylation, alkenyllithium reagents.

ChemInform Abstract: Five- and Six-Membered Ring Opening of Pyroglutamic Diketopiperazine.

ChemInform ◽  
2010 ◽  
Vol 33 (34) ◽  
pp. no-no
Author(s):  
Dennis A. Parrish ◽  
Lon J. Mathias
Keyword(s):  
Ring Opening ◽  
Membered Ring

Unravelling the Mechanism and Selectivity of the NHC‐catalyzed Three‐Membered Ring‐Opening/Fluorination of Epoxy Enals: A DFT Study

ChemCatChem ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2919-2925 ◽  
Author(s):  
Yang Wang ◽  
Ling‐Bo Qu ◽  
Yu Lan ◽  
Donghui Wei
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Dft Study

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

An Unexpected Synthesis of Novel Oxygen-Bridged 1,5-Benzothiazepine Derivatives and their Reductive Five-Membered-Ring Opening

2000 ◽  
Vol 131 (4) ◽  
pp. 0393-0400 ◽  
Author(s):  
Roshan Ahmad ◽  
Mohammad Zia-ul-Haq ◽  
Shahid Hameed ◽  
Humaira Akhtar ◽  
Helmut Duddeck
Keyword(s):  
Ring Opening ◽  
Membered Ring

Synthesis of Four-Membered Ring Spiro-β-lactams by Epoxide Ring-Opening.

ChemInform ◽  
2007 ◽  
Vol 38 (43) ◽  
Author(s):  
Fides Benfatti ◽  
Giuliana Cardillo ◽  
Luca Gentilucci ◽  
Alessandra Tolomelli
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Epoxide Ring ◽  
Epoxide Ring Opening

Biotransformation of Glabratephrin, a Rare Type of Isoprenylated Flavonoids, by Aspergillus niger

2008 ◽  
Vol 63 (7-8) ◽  
pp. 561-564 ◽  
Author(s):  
Abou-El-Hamd H Mohamed ◽  
Ali K. Khalafallah ◽  
Afifi H. Yousof
Keyword(s):  
Aspergillus Niger ◽  
Ring Opening ◽  
Microbial Transformation ◽  
Membered Ring ◽  
Nmr Studies ◽  
Rare Type ◽  
Tephrosia Purpurea ◽  
Isolated Compound

Microbial transformation of glabratephrin, the major isolated compound from Tephrosia purpurea, afforded pseudosemiglabrin. The formation of the transformed compound seems to be performed via ring opening-closure of a five-membered ring causing transformation from a spiro into a fused system. The structure of the transformed compound was determined by comprehensive NMR studies, including DEPT, COSY, HMQC, NOE and MS.

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