Cyclopropyl Building Blocks for Organic Synthesis. Part 118. A Two-Step Four-Component Queuing Cascade Involving a Heck Coupling, π-Allylpalladium Trapping and Diels—Alder Reaction.

ChemInform ◽  
2006 ◽  
Vol 37 (12) ◽  
Author(s):  
Baris Yuecel ◽  
Lars Arve ◽  
Armin de Meijere
Keyword(s):  
Organic Synthesis ◽  
Building Blocks ◽  
Alder Reaction ◽  
Diels Alder ◽  
Heck Coupling ◽  
Diels Alder Reaction

Enantioselective Syntheses of Flavonoid Diels-Alder Natural Products: A Review

2018 ◽  
Vol 15 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Shah Bakhtiar Nasir ◽  
Noorsaadah Abd Rahman ◽  
Chin Fei Chee
Keyword(s):  
Natural Products ◽  
Organic Synthesis ◽  
Lewis Acid ◽  
Alder Reaction ◽  
Diels Alder ◽  
Enantioselective Synthesis ◽  
Chiral Ligand ◽  
Asymmetric Syntheses ◽  
Diels Alder Reaction ◽  
Enantioselective Syntheses

Background: The Diels-Alder reaction has been widely utilised in the syntheses of biologically important natural products over the years and continues to greatly impact modern synthetic methodology. Recent discovery of chiral organocatalysts, auxiliaries and ligands in organic synthesis has paved the way for their application in Diels-Alder chemistry with the goal to improve efficiency as well as stereochemistry. Objective: The review focuses on asymmetric syntheses of flavonoid Diels-Alder natural products that utilize chiral ligand-Lewis acid complexes through various illustrative examples. Conclusion: It is clear from the review that a significant amount of research has been done investigating various types of catalysts and chiral ligand-Lewis acid complexes for the enantioselective synthesis of flavonoid Diels-Alder natural products. The results have demonstrated improved yield and enantioselectivity. Much emphasis has been placed on the synthesis but important mechanistic work aimed at understanding the enantioselectivity has also been discussed.

scholarly journals Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

2010 ◽  
Vol 6 ◽  
Author(s):  
Satoru Arimitsu ◽  
Gerald B Hammond
Keyword(s):  
Building Blocks ◽  
Alder Reaction ◽  
Diels Alder ◽  
Tandem Reaction ◽  
Enyne Metathesis ◽  
Metathesis Reaction ◽  
Ring Closing Metathesis ◽  
Diels Alder Reaction

gem-Difluoro-1,7-enyne amides are suitable building blocks for the synthesis of difluorodihydropyridinones via a ring-closing metathesis reaction, and of 4,4-difluoro-3-oxoisoquinolines through a ring-closing metathesis–enyne metathesis tandem reaction. These products, in turn, undergo a Diels–Alder reaction to yield heterotricyclic systems in moderate to good yields.

scholarly journals Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

2020 ◽  
Vol 16 ◽  
pp. 2757-2768
Author(s):  
Viola Kolaříková ◽  
Markéta Rybáčková ◽  
Martin Svoboda ◽  
Jaroslav Kvíčala
Keyword(s):  
Triple Bond ◽  
Building Blocks ◽  
Ester Group ◽  
Alder Reaction ◽  
Diels Alder ◽  
Side Reactions ◽  
Enyne Metathesis ◽  
Ring Closing Metathesis ◽  
2Nd Generation ◽  
Diels Alder Reaction

The prochiral 4-(allyloxy)hepta-1,6-diynes, optionally modified in the positions 1 and 7 with an alkyl or ester group, undergo a chemoselective ring-closing enyne metathesis yielding racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans. Among the catalysts tested, Grubbs 1st generation precatalyst in the presence of ethene (Mori conditions) gave superior results compared to the more stable Grubbs or Hoveyda–Grubbs 2nd generation precatalysts. This is probably caused by a suppression of the subsequent side-reactions of the enyne metathesis product with ethene. On the other hand, the 2nd generation precatalysts gave better yields in the absence of ethene. The metathesis products, containing both a triple bond and a conjugated system, can be successfully orthogonally modified. For example, the metathesis product of 5-(allyloxy)nona-2,7-diyne reacted chemo- and stereoselectively in a Diels–Alder reaction with N-phenylmaleimide affording the tricyclic products as a mixture of two separable diastereoisomers, the configuration of which was estimated by DFT computations. The reported enediyne metathesis paves the way to the enantioselective enyne metathesis yielding chiral building blocks for compounds with potential biological activity, e.g., norsalvinorin or cacospongionolide B.

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