A [3,3]-sigmatropic shift in Diels–Alder adducts of fulvenes: an example of a reverse–Claisen rearrangement

1968 ◽  
Vol 0 (10) ◽  
pp. 587-588 ◽  
Author(s):  
M. T. Hughes ◽  
R. O. Williams
Keyword(s):  
Claisen Rearrangement ◽  
Diels Alder ◽  
Sigmatropic Shift

Intramolecular Diels-Alder Cycloaddition: 7-Isocyanoamphilecta- 11(20),15-diene (Miyaoka), (–)-Scabronine G (Kanoh), Basiliolide B (Stoltz), Hirsutellone B (Uchiro), Echinopine A (Chen)

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Neurotrophic Factors ◽  
Claisen Rearrangement ◽  
Diels Alder ◽  
Relative Configuration ◽  
Intramolecular Cycloaddition ◽  
Quaternary Centers ◽  
Astrocytoma Cells ◽  
National University ◽  
Seoul National University ◽  
1321N1 Astrocytoma

The amphilectane diterpenes, exemplified by 7-isocyanoamphilecta-11(20),15-diene 3, have been little investigated. In the course of a synthesis of 3, Hiroaki Miyaoka of the Tokyo University of Pharmacy and Life Sciences took advantage (Synlett 2011, 547) of the kinetic enolization and silylation of 1 to convert it into a trienone that spontaneously cyclized to 2. Scabronine G 6, isolated from the mushroom Sarcodon scabrosus, was found to enhance the secretion of neurotrophic factors from 1321N1 astrocytoma cells. To set the absolute configuration of the two quaternary centers that are 1, 4 on the cyclohexane ring of 6, Naoki Kanoh and Yoshiharu Iwabuchi of Tohoku University cyclized (Org. Lett. 2011, 13, 2864) 4 to 5. Although described by the authors as a double Michael addition, this transformation has the same connectivity as an intramolecular Diels-Alder cycloaddition. The diterpenes isolated from the genus Thapsia, represented by basiliolide B 9, induce rapid mobilization of intracellular Ca2+ stores. Brian M. Stoltz of Caltech effected (Angew. Chem. Int. Ed. 2011, 50, 3688) Claisen rearrangement of 7 to give an intermediate that cyclized to 8 as a mixture of diastereomers. A significant challenge in the synthesis was the assembly of the delicate enol ether/lactone of 9. Hirsutellone B 12, isolated from Hirsutella nivea, shows significant antituberculosis activity. Hiromi Uchiro of the Tokyo University of Science found it useful (Org. Lett. 2011, 13, 6268) to protect the intermediate unsaturated keto ester by intermolecular cycloaddition with pentamethylcyclopentadiene before constructing the triene of 10. Simple thermolysis reversed the intermolecular addition, opening the way to intramolecular cycloaddition to give 11. The tetracyclic ring system of the diterpene echinopine A 15 represents a substantial synthetic challenge. David Y.-K. Chen of Seoul National University approached this problem (Org. Lett. 2011, 13, 5724) by Pd-mediated cyclization of 13 to the diene, which then underwent intramolecular Diels-Alder cycloaddition to give 14, with control of the relative configuration of two of the three ternary centers of 15. Double bond migration followed by oxidative cleavage of the resulting cyclohexenone then set the stage for the intramolecular cyclopropanation that completed the synthesis of 15.

Total Synthesis of (±)-Cassumunins A–C and Curcumin Analogues

Synthesis ◽  
2020 ◽  
Vol 52 (10) ◽  
pp. 1561-1575 ◽  
Author(s):  
Faiz Ahmed Khan ◽  
Mulla Althafh Hussain
Keyword(s):  
Total Synthesis ◽  
Claisen Rearrangement ◽  
Aldol Condensation ◽  
Coupling Reaction ◽  
Cross Coupling ◽  
Full Account ◽  
Curcumin Analogues ◽  
Cross Coupling Reaction ◽  
Sigmatropic Shift ◽  
Novel Approaches

A full account of the total synthesis of (±)-cassumunins A–C – superior antioxidants and anti-inflammatory agents – is given. Two novel approaches were developed for synthesizing cassumunins. The total synthesis of cassumunins A and B was accomplished in five linear steps from a known aldehyde in good overall yields of 50 and 43%, respectively, featuring a cascade [3,3]-sigmatropic shift (the Claisen rearrangement) and Heck cross-coupling reaction. Consequently, the total synthesis of cassumunin C was accomplished in three linear steps from a known alcohol with an overall yield of 53%. The key features involved in this synthesis are tandem [3,3]-sigmatropic shift, SN2′ reaction, and aldol condensation. Moreover, a total of eighteen symmetrical and unsymmetrical curcumin analogues were synthesized.

Ring-Closing Metathesis Approach to Cage Propellanes Containing Oxepane and Tetrahydrofuran Hybrid System

Synthesis ◽  
2017 ◽  
Vol 49 (24) ◽  
pp. 5339-5350 ◽  
Author(s):  
Sambasivarao Kotha ◽  
Subba Cheekatla ◽  
Darshan Mhatre
Keyword(s):  
Claisen Rearrangement ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ring Closing Metathesis ◽  
Cage Compounds ◽  
Transannular Cyclization ◽  
Diels Alder Reaction ◽  
Grignard Addition ◽  
Key Steps ◽  
First Time

The preparation of a variety of structurally interesting oxygenated cage compounds involving atom-economic processes such as Claisen rearrangement, Diels–Alder reaction, [2+2] photocycloaddition, and ring-closing metathesis (RCM) as key steps is reported. For the first time, oxepane ring system is introduced in cage framework using olefin metathesis as a key step. These cage systems assembled here are difficult to prepare by traditional methods. The synthetic sequence described here opens up new routes to higher order polycycles containing heteroatoms without the involvement of protecting groups. Transannular cyclization observed during Grignard addition and the RCM protocol used here may be applicable to generate unknown oxygenated cage systems.

Intramolecular Diels–Alder Reactions: Diastereofacial Selectivity and Coupling with an Aliphatic Claisen Rearrangement

1991 ◽  
Vol 30 (4) ◽  
pp. 414-416 ◽  
Author(s):  
Johann Mulzer ◽  
Harald Bock ◽  
Wolfgang Eck ◽  
Jürgen Buschmann ◽  
Peter Luger
Keyword(s):  
Claisen Rearrangement ◽  
Diels Alder
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