Highly enantioselective synthesis of naphthoquinones and pyranonaphthoquinones catalyzed by bifunctional chiral bis-squaramides

2015 ◽  
Vol 13 (18) ◽  
pp. 5243-5254 ◽  
Author(s):  
Nagaraju Molleti ◽  
Vinod K. Singh
Keyword(s):  
Conjugate Addition ◽  
Enantioselective Synthesis ◽  
High Yields

A variety of enantioenriched naphthoquinones has been synthesized in high yields and excellent enantioselectivities (up to >99% ee) using a bifunctional chiral bis-squaramide catalyzed conjugate addition of 2-hydroxy-1,4-naphthoquinone to 2-enoylpyridines.

Lithiated three-membered heterocycles as chiral nucleophiles in the enantioselective synthesis of 1-oxaspiro[2,3]hexanes

2021 ◽  
Author(s):  
Andrea Cocco ◽  
Maria Grazia Rubanu ◽  
Maria Laura Sechi ◽  
Angelo Frongia ◽  
Pietro Mastrorilli ◽  
...  
Keyword(s):  
Styrene Oxide ◽  
Enantioselective Synthesis ◽  
High Yields

Enantiomerically enriched oxaspiro- and azaspirohexanes were synthesized through a two-step addition of configurably stable Li-styrene oxide (or aziridine) to 3-substituted cyclobutanones and base-mediated Payne rearrangement sequence with high yields and selectivity.

Copper-catalyzed 1,6-conjugate addition of para-quinone methides with diborylmethane

2021 ◽  
Author(s):  
Xin Li ◽  
Guoliang Gao ◽  
Songtao He ◽  
Qiuling Song
Keyword(s):  
Catalytic System ◽  
Conjugate Addition ◽  
Quinone Methides ◽  
High Yields

Presented herein is the first 1,6-conjugate addition of diborylmethane, which is promoted by a simple and inexpensive copper catalytic system. This method features high yields, good selectivities and broad functional...

scholarly journals Enantioselective synthesis of seven-membered carbo- and heterocyles by organocatalyzed intramolecular Michael addition

RSC Advances ◽  
2016 ◽  
Vol 6 (36) ◽  
pp. 30166-30169 ◽  
Author(s):  
James O. Guevara-Pulido ◽  
José M. Andrés ◽  
Deisy P. Ávila ◽  
Rafael Pedrosa
Keyword(s):  
Michael Addition ◽  
Enantioselective Synthesis ◽  
High Yields

Enantioenriched seven membered rings have been prepared in high yields and stereoselectivities by intramolecular Michael addition of functionalized enals catalyzed by Jorgensen–Hayashi catalyst.

Catalytic Enantioselective Synthesis of Chiral Spirocyclic 1,3-Diketones via Organo-Cation Catalysis

2021 ◽  
Author(s):  
Xiao-Yan Zhang ◽  
Ya-Ping Shao ◽  
Bao-Kuan Guo ◽  
Kun Zhang ◽  
Fu-Min Zhang ◽  
...  
Keyword(s):  
Enantioselective Synthesis ◽  
High Yields ◽  
Convenient Access

An SPA-triazolium bromide catalyzed transannular C-acylation of enol lactones is presented. This methodology provides convenient access to a range of enantioenriched spirocyclic 1,3-diketones in moderate to high yields and enantioselectivities...

The Toste Synthesis of ( + )-Fawcettimine

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Current Method ◽  
Conjugate Addition ◽  
Enantioselective Synthesis ◽  
University Of California ◽  
Lycopodium Alkaloid ◽  
Silyl Enol Ether ◽  
Terminal Alkene ◽  
Robinson Annulation ◽  
The University ◽  
Stereogenic Center

The tetracyclic Lycopodium alkaloid fawcettimine 3 and its derivatives are of interest as inhibitors of acetylcholine esterase. F. Dean Toste of the University of California, Berkeley recently reported (Angew. Chem. Int. Ed. 2007, 46, 7671) the first enantioselective synthesis of 3. The key to the synthesis was the rapid assembly of the enantiomerically-enriched hydrindane 2. The preparation of 2 began with the enantioselective Robinson annulation of the β-keto ester 4 with crotonaldehyde 5, mediated by the organocatalyst 6. In this protocol, originally developed by Karl Anker Jørgensen, the single stereogenic center was established by conjugate addition, presumably to the chiral iminium salt generated by the condensation of 5 with 6. Subsequent aldol (or more likely Mannich) cyclization followed by elimination gave 7. Hydrolysis and decarboxylation by heating with p-TsOH converted 7 to 1. This procedure was robust enough to allow preparation of a ten gram batch of 1. This Jørgensen annulation is the current method of choice for the enantioselective preparation of 2,5-dialkyl cyclohexenones. Conjugate addition of the propargyl anion equivalent 8 to 1 proceeded with the expected > 95:5 axial diastereoselectivity, to give the silyl enol ether 9. Exposure of the derived iodide 10 to catalytic [Ph3 PAu]Cl and AgBF4 induced smooth cyclization to the cis hydrindane 2. Before constructing the nine-membered ring amine of fawcettimine 3, it was first necessary to protect the ketone as the ketal. Pd-mediated coupling of the alkenyl iodide with the organoborane derived from 11 then proceeded smoothly, as did the subsequent hydroboration of the terminal alkene. Neither the mesylate nor the tosylate derived from 12 could be induced to cyclize. In contrast, intramolecular displacement of the iodide proceeded well, to give 13. Hydroboration followed by oxidation then gave 15, which on deprotection cyclized to (+)-fawcettimine 3. Several aspects of this synthesis are attractive. While the stereochemical outcome of the hydroboration of 14 could not necessarily be predicted with confidence, in fact it did not matter, as the stereogenic center adjacent to the ketone could be epimerized under the trifluoroacetic acid deprotection conditions, and only the desired diastereomer would be able to add in an intramolecular fashion to the cyclohexanone.

scholarly journals Organocatalytic Asymmetric Aldol Reaction of Arylglyoxals and Hydroxyacetone: Enantioselective Synthesis of 2,3-Dihydroxy-1,4-diones

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 648
Author(s):  
Yu-Hao Zhou ◽  
Yu-Zu Zhang ◽  
Zhu-Lian Wu ◽  
Tian Cai ◽  
Wei Wen ◽  
...  
Keyword(s):  
Primary Amine ◽  
Aldol Reaction ◽  
Enantioselective Synthesis ◽  
Asymmetric Aldol ◽  
Highly Efficient ◽  
Asymmetric Aldol Reaction ◽  
Aldol Addition ◽  
High Yields

A highly efficient quinine-derived primary-amine-catalyzed asymmetric aldol addition of hydroxyacetone to arylglyoxals is described. Structurally diverse anti-2,3-dihydroxy-1,4-diones were generated in high yields, with good diastereoselectivities and enantioselectivities.

Non-hydrogen bond catalyst-mediated diastereoselective conjugate additions of 5H-oxazol-4-ones to o-hydroxyphenyl-substituted p-quinone methides

2020 ◽  
Vol 18 (35) ◽  
pp. 6807-6811
Author(s):  
Ziyang Wang ◽  
Anqi Huang ◽  
Fang Fang ◽  
Pengfei Li ◽  
Guokai Liu ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Conjugate Addition ◽  
Quinone Methides ◽  
Conjugate Additions ◽  
High Yields

An efficient DBU-catalyzed conjugate addition of 5H-oxazol-4-ones to o-hydroxyphenyl-substituted p-quinone methides has been developed, affording the valuable diarylmethanes in high yields with excellent diastereoselectivity.

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