The Rationale for Stereoinduction in Conjugate Addition to Alkylidenemalonates Bearing a Menthol-derived Chiral Auxiliary

Tetrahedron ◽  
2021 ◽  
pp. 132220
Author(s):  
Ken-ichi Yamada ◽  
Shinichi Fujiwara ◽  
Tsubasa Inokuma ◽  
Masayuki Sugano ◽  
Yousuke Yamaoka ◽  
...  
Keyword(s):  
Conjugate Addition ◽  
Chiral Auxiliary

scholarly journals Oxazolidinones as Chiral Auxiliaries in the Asymmetric 1,4-Conjugate Addition Reaction Applied to the Total Synthesis of Natural Products: A Supplemental Mini-Review

2018 ◽  
Vol 15 (1) ◽  
pp. 3-20 ◽  
Author(s):  
Vahideh Zadsirjan ◽  
Majid M. Heravi
Keyword(s):  
Total Synthesis ◽  
Biological Activities ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Addition Reactions ◽  
Chiral Auxiliaries ◽  
Complex Molecules ◽  
Total Syntheses ◽  
Naturally Occurring ◽  
Wide Range

Background: The most frequently used chiral auxiliaries, oxazolidinones (Evans' oxazolidinones) have been employed in 1,4-congugate addition reactions to α,β-unsaturated carbonyl compounds. Supplementary to our previous reports in this mini-review, we attempted to underscore the applications of this strategy in a step (steps) in the total synthesis of some naturally occurring compounds exhibiting diverse biological activities. Objective: In this mini-review, we try to underscore the applications of oxazolidinones (Evans’ oxazolidinones) in 1,4-congugate addition reactions to α,β-unsaturated carbonyl in the total synthesis of some naturally occurring compounds exhibiting diverse biological activities. Conclusion: In spite of well-known superiority of asymmetric catalyzed reactions, the use of auxiliarycontrolled reactions are still considered as commanding, vital and sometimes as only tools in the generation of stereogenic centers during the construction of complex molecules and total synthesis of naturally occurring compounds. The commercial availability, or readily accessibility of a wide variety of chiral amino alcohols as starting materials to synthesize a wide range of oxazolidinones is the merits of them. In addition, the ease of removal and subjection to various and diverse stereoselective reactions make oxazolidinones as the ideal and superior chiral auxiliaries. In this regard, they were successfully used in asymmetric 1,4-conjugate addition reactions with high stereoselectivities. The high degree of asymmetric induction can be attributed to the rigid chelation of N-acyloxazolidinones with metal ions, as well as the covering of one face of the system by the bulkiness of 4-substituent. In summary, in this report, the importance of the applications of chiral oxazolidinones as suitable chiral auxiliaries in the stereoselective, 1,4-conjugate addition reactions in asymmetric synthesis and in particular, the total synthesis of naturally occurring compounds and some complex molecules were underscored. Noticeably, in these total syntheses, this chiral auxiliary is controlling the stereochemistry of a newly created stereogenic center as well as preserving the configuration of other chiral centers, which already have been presented in the precursor. General methods have been established for the attachment of the chiral auxiliary as a moiety to the substrate molecule in high to excellent yields. At the end of these reactions, this auxiliary can be easily removed leaving various desired reactive motifs for the next step in multi-step synthesis.

Diasteroselective conjugate addition of diethylaluminum cyanide to a conjugated N-enoyl system: an alternative synthesis of (S)-pregabalin

2014 ◽  
Vol 92 (1) ◽  
pp. 45-48 ◽  
Author(s):  
Erika Tovar-Gudiño ◽  
Rosmarbel Morales-Nava ◽  
Mario Fernández-Zertuche
Keyword(s):  
Amino Acids ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Alternative Synthesis ◽  
Practical Synthesis

We have explored in this work the conjugate addition of diethylaluminum cyanide (Nagata’s reagent) to an N-enoyl system bearing the (R)-4-phenyl-2-oxazolidinone chiral auxiliary. Since this method provided a practical synthesis of γ-amino acids, we report the conjugate addition of diethylaluminum cyanide as the key step in the synthesis of (S)-pregabalin 1 in a five-step sequence of reactions from commercially available starting materials.

Construction of Arrays of Stereogenic Centers: The Zhang Synthesis of (+)-Podophyllotoxin

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Organic Chemistry ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Stanford University ◽  
Enol Ethers ◽  
University Of Technology ◽  
Stereogenic Centers ◽  
Diastereoselective Addition ◽  
University Of Bristol ◽  
The University

Varinder K. Aggarwal of the University of Bristol showed (Angew. Chem. Int. Ed. 2009, 48, 1149) that condensation of a boronic ester 2 with a metalated aziridine 1 led, after oxidation, to the defined amino alcohol 3. Hisashi Yamamoto of the University of Chicago developed (Angew. Chem. Int. Ed. 2009, 48, 3333) conditions for the diastereoselective addition of an organometallic to an α-nitrosylated aldehyde, to give, after reduction, the diol 6. Xiaoyu Wu of Shanghai University and Gang Zhao of the Shanghai Institute of Organic Chemistry designed (Adv. Synth. Cat. 2009, 351, 158) an organocatalyst that mediated the enantioselective addition of hydroxyacetone 7 to a range of aldehydes. Andrew G. Myers of Harvard University found (J. Am. Chem. Soc. 2009, 131, 5763) that trialkylaluminum reagents opened epoxides of enol ethers at the more substituted position, delivering protected diols such as 10. Keiji Maruoka of Kyoto University created (Angew. Chem. Int. Ed. 2009, 48, 1838) an organocatalyst for the addition of an aldehyde 11 to an imine 12, to give 13. Markus Kalesse of Leibnitz Universität Hannover showed (Tetrahedron Lett. 2009, 50, 3485) that an organocatalyst could mediate the selective γ-reactivity of 15, leading to 16. Barry M. Trost of Stanford University found (J. Am. Chem. Soc. 2009, 131, 1674) that an organocatalyst directed the addition of diazoacetate 18 to an aldehyde, to give, after further reaction with a trialkylborane, the syn aldol product 19. Professor Trost also demonstrated (J. Am. Chem. Soc. 2009, 131, 4572) that a related complex mediated the conjugate addition of 22 to 21. Enantioselective construction of arrays of alkylated stereogenic centers is a particular challenge. Ji Zhang, then at Pfizer, found (Tetrahedron Lett. 2009, 50, 1167) that the chiral auxiliary of 24 directed both the conjugate addition and the subsequent protonation, and also allowed the product 25 to be brought to > 98% purity by crystallization. Tönis Kanger of Tallinn University of Technology developed (J. Org. Chem. 2009, 74, 3772) an organocatalyst for the conjugate addition of aldehydes to nitrostyrenes such as 26 to give 27.

scholarly journals Bis-Cyclometalated Indazole and Benzimidazole Chiral-at-Iridium Complexes: Synthesis and Asymmetric Catalysis

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1822
Author(s):  
Sebastian Brunen ◽  
Yvonne Grell ◽  
Philipp S. Steinlandt ◽  
Klaus Harms ◽  
Eric Meggers
Keyword(s):  
Asymmetric Catalysis ◽  
Coordination Sphere ◽  
Conjugate Addition ◽  
Chiral Auxiliary ◽  
Iridium Complexes ◽  
Bidentate Ligands ◽  
Nazarov Cyclization ◽  
Tert Butyl ◽  
New Class ◽  
Acyl Imidazole

A new class of bis-cyclometalated iridium(III) catalysts containing two inert cyclometalated 6-tert-butyl-2-phenyl-2H-indazole bidentate ligands or two inert cyclometalated 5-tert-butyl-1-methyl-2-phenylbenzimidazoles is introduced. The coordination sphere is complemented by two labile acetonitriles, and a hexafluorophosphate ion serves as a counterion for the monocationic complexes. Single enantiomers of the chiral-at-iridium complexes (>99% er) are obtained through a chiral-auxiliary-mediated approach using a monofluorinated salicyloxazoline and are investigated as catalysts in the enantioselective conjugate addition of indole to an α,β-unsaturated 2-acyl imidazole and an asymmetric Nazarov cyclization.

Asymmetric conjugate addition reaction by the use of ()-γ-trityloxymethyl-γ-butyrolactam as a chiral auxiliary

1986 ◽  
Vol 27 (3) ◽  
pp. 369-372 ◽  
Author(s):  
Kiyoshi Tomioka ◽  
Toshiro Suenaga ◽  
Kenji Koga
Keyword(s):  
Addition Reaction ◽  
Conjugate Addition ◽  
Chiral Auxiliary

scholarly journals Tandem Asymmetric Conjugate Addition/α-Alkylation Using (S,S)-(+)-Pseudoephedrine as Chiral Auxiliary.

ChemInform ◽  
2006 ◽  
Vol 37 (43) ◽  
Author(s):  
Efraim Reyes ◽  
Jose L. Vicario ◽  
Luisa Carrillo ◽  
Dolores Badia ◽  
Ainara Iza ◽  
...  
Keyword(s):  
Conjugate Addition ◽  
Chiral Auxiliary
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