ChemInform Abstract: Diastereoselective Zwitterionic Aza-Claisen Rearrangement: Synthesis of Nine-Membered Ring Lactams and Transannular Ring Contraction.

ChemInform ◽  
2010 ◽  
Vol 27 (44) ◽  
pp. no-no
Author(s):  
M. DIEDERICH ◽  
U. NUBBEMEYER
Keyword(s):  
Claisen Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

ChemInform Abstract: [3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines.

ChemInform ◽  
2016 ◽  
Vol 47 (21) ◽  
Author(s):  
Aurelie Mace ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossio ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

C-O Ring Containing Natural Products: Paeonilactone B (Taylor), Deoxymonate B (de la Pradilla), Sanguiin H-5 (Spring), Solandelactone A (White), Spirastrellolide A (Paterson)

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Oxidative Coupling ◽  
Claisen Rearrangement ◽  
Cyclic Carbonate ◽  
Membered Ring ◽  
State University ◽  
Enantiomerically Pure ◽  
University Of Cambridge ◽  
Spirastrellolide A ◽  
The University ◽  
Oregon State University

Richard J. K. Taylor of the University of York has developed (Angew. Chem. Int. Ed. 2008, 47, 1935) the diasteroselective intramolecular Michael cyclization of phosphonates such as 2. Quenching of the cyclized product with paraformaldehyde delivered ( + )-Paeonilactone B 3. Roberto Fernández de la Pradilla of the CSIC, Madrid established (Tetrahedron Lett. 2008, 49, 4167) the diastereoselective intramolecular hetero Michael addition of alcohols to enantiomerically-pure acyclic sulfoxides such as 4 to give the allylic sulfoxide 5. Mislow-Evans rearrangement converted 5 into 6, the enantiomerically-pure core of Ethyl Deoxymonate B 7. The ellagitannins, represented by 10, are single atropisomers around the biphenyl linkage. David R. Spring of the University of Cambridge found (Organic Lett. 2008, 10, 2593) that the chiral constraint of the carbohydrate backbone of 9 directed the absolute sense of the oxidative coupling of the mixed cuprate derived from 9, leading to Sanguiin H-5 10 with high diastereomeric control. A key challenge in the synthesis of the solandelactones, exemplified by 14, is the stereocontrolled construction of the unsaturated eight-membered ring lactone. James D. White of Oregon State University found (J. Org. Chem. 2008, 73, 4139) an elegant solution to this problem, by exposure of the cyclic carbonate 11 to the Petasis reagent, to give 12. Subsequent Claisen rearrangement delivered the eight-membered ring lactone, at the same time installing the ring alkene of Solandelactone E 14. AD-mix usually proceeds with only modest enantiocontrol with terminal alkenes. None the less, Ian Paterson, also of the University of Cambridge, observed (Angew. Chem. Int. Ed. 2008, 47, 3016, Angew. Chem. Int. Ed. 2008, 47, 3021) that bis-dihydroxylation of the diene 17 proceeded to give, after acid-mediated cyclization, the bis-spiro ketal core 18 of Spirastrellolide A Methyl Ester 19 with high diastereocontrol.

Hypervalent iodine reagent-mediated reactions involving rearrangement processes

2020 ◽  
Vol 56 (91) ◽  
pp. 14119-14136
Author(s):  
Beibei Zhang ◽  
Xiaoxian Li ◽  
Boying Guo ◽  
Yunfei Du
Keyword(s):  
Claisen Rearrangement ◽  
Beckmann Rearrangement ◽  
Hypervalent Iodine ◽  
Ring Contraction ◽  
Hofmann Rearrangement ◽  
Rearrangement Processes

We summarize the developments of hypervalent iodine reagents-mediated reactions involving [1,2]-migration, Hofmann rearrangement, Beckmann rearrangement, ring contraction/expansion, [3,3]-sigmatropic/iodonium-Claisen rearrangement and some miscellaneous rearrangements.

Untersuchungen zur Ringkontraktion am 1,4-Dithia-2,6-diaza-3,5-diborinan-System/ Studies on Ring Contraction of the l,4-Dithia-2,6-diaza-3,5-diborinane System

1988 ◽  
Vol 43 (8) ◽  
pp. 959-962 ◽  
Author(s):  
Carl Habben ◽  
Anton Meiler ◽  
Stefan Pusch
Keyword(s):  
Mass Spectra ◽  
Ring System ◽  
Membered Ring ◽  
Ring Contraction ◽  
C Nmr

AbstractThe 1,4-dithia-2,6-diaza-3,5-diborinanes 1a-d react with elemental sodium with formation of the 1,3-diaza-2,4-diboretidines 2a-d. By use of more sodium in case of 1 d or 3,5-bis(diethylamino)- 2-cyclohexyl-6-trimethylsilyldiborinane, the 1,3-thiaza-2,4-diboretidines 3 were formed. 3.5-Dimethyl-2,6-bis(trimethylsilyl)-1,4-dithia-2,6-diaza-3,5-diborinane gives the borazine 4, The reaction of di-t-butyl-sulfurdiimide with 2,6-di-t-butyl-3,5-dimethyl-1,4-dithia-2,6-diaza-3,5-diborinane leads by ring contraction to the four-membered ring system 5. 1H, 11B, 13C NMR and mass spectra are reported and discussed.

[3,3]-Sigmatropic Rearrangement/Allylboration/Cyclization Sequence: Enantioenriched Seven-Membered-Ring Carbamates and Ring Contraction to Pyrrolidines

2015 ◽  
Vol 55 (3) ◽  
pp. 1025-1029 ◽  
Author(s):  
Aurélie Macé ◽  
Sabrina Touchet ◽  
Patricia Andres ◽  
Fernando Cossío ◽  
Vincent Dorcet ◽  
...  
Keyword(s):  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Contraction

Organocatalysis of Carbocyclic Construction: The MacMillan Synthesis of (+)-Frondosin B

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Claisen Rearrangement ◽  
Kinetic Resolution ◽  
Membered Ring ◽  
Max Planck ◽  
Princeton University ◽  
Michael Condensation ◽  
Carbocyclic Rings ◽  
Robinson Annulation ◽  
Technological University

One of the more powerful applications of organocatalysis has been the enantioselective transformation of preformed prochiral rings. In the five-membered ring series, Nobuyuki Mase of Shizuoka University effected (Synlett 2010, 2340) enantioselective addition of malonate to cyclopentenone 1, and Eric N. Jacobsen of Harvard University devised (Angew. Chem. Int. Ed. 2010, 49, 9753) a guanidinium catalyst for the Claisen rearrangement of 4 to 5. Jacek Mlynarski of Jagiellonian University accomplished (Tetrahedron Lett. 2010, 51, 4088) the enantioselective hydroxymethylation of 6. This worked equally well for cyclopentanone and cycloheptanone. The dynamic kinetic resolution/reductive amination of 8 described (Angew. Chem. Int. Ed. 2010, 49, 4612) by Benjamin List of the Max-Planck-Institut Mülheim worked best with cyclohexanones such as 8. Organocatalysts can also be effective for the construction of carbocyclic rings. Teck-Peng Loh of Nanyang Technological University found (Chem. Sci. 2010, 1, 739) a commercial phosphine catalyst that efficiently mediated the condensation of 10 with 11. David W. C. MacMillan of Princeton University used (J. Am. Chem. Soc. 2010, 132, 10015) a SOMO catalyst to combine 13 with 14 to make 15. Dawei Ma of the Shanghai Institute of Organic Chemistry employed (Org. Lett. 2010, 12, 3634) the Hayashi catalyst in the double Michael condensation of 16 with 17. Daniel Romo of Texas A&M University showed (Org. Lett. 2010, 12, 3764) that the appropriate organocatalyst could direct 19 to either diastereomer of the β-lactone 20. Professor Romo also reported (Angew. Chem. Int. Ed. 2010, 49, 9479) the desymmetrization of 2-alkyl cyclohexane-1,3-diones using a similar approach. In the six-membered ring series, José Alemán and José Luis García Ruano of the Universidad Autónoma de Madrid carried out (Eur. J. Org. Chem. 2010, 4482) Robinson annulation of 17 with 21. Ying-Chun Chen of Sichuan University, again using the Hayashi catalyst, reported (Angew. Chem. Int. Ed. 2010, 49, 6418) the addition of 17 to 23 to give 24. In another elegant application of visible light–mediated organocatalysis, Professor MacMillan described (Chem. Sci. 2010, 1, 37) the addition of the commercial boronic acid 25 to 17.

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