ChemInform Abstract: Highly Enantioselective Synthesis of Chiral Allenes by Sequential Creation of Stereogenic Center and Chirality Transfer in a Single Pot Operation.

ChemInform ◽  
2012 ◽  
Vol 43 (39) ◽  
pp. no-no
Author(s):  
Mariappan Periasamy ◽  
Nalluri Sanjeevakumar ◽  
Manasi Dalai ◽  
Ramani Gurubrahamam ◽  
Polimera Obula Reddy
Keyword(s):  
Enantioselective Synthesis ◽  
Chirality Transfer ◽  
Stereogenic Center

Highly Enantioselective Synthesis of Chiral Allenes by Sequential Creation of Stereogenic Center and Chirality Transfer in a Single Pot Operation

2012 ◽  
Vol 14 (12) ◽  
pp. 2932-2935 ◽  
Author(s):  
Mariappan Periasamy ◽  
Nalluri Sanjeevakumar ◽  
Manasi Dalai ◽  
Ramani Gurubrahamam ◽  
Polimera Obula Reddy
Keyword(s):  
Enantioselective Synthesis ◽  
Chirality Transfer ◽  
Stereogenic Center

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.

Golden opportunities in catalysis

2008 ◽  
Vol 80 (5) ◽  
pp. 1063-1069 ◽  
Author(s):  
Norbert Krause ◽  
Volker Belting ◽  
Carl Deutsch ◽  
Jörg Erdsack ◽  
Hong-Tao Fan ◽  
...  
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
High Reactivity ◽  
Donor Ligands ◽  
Cyclization Product ◽  
Chirality Transfer ◽  
Key Features ◽  
Stereogenic Center

The gold-catalyzed endo-cycloisomerization of allenes bearing nucleophilic substituents in the α- or β-position opens up a versatile access to various five- and six-membered heterocycles. Key features of these transformations are the high reactivity of the allene in the presence of Lewis-acidic, carbophilic gold(I) or gold(III) catalysts, and the chirality transfer from the allenic axis of chirality to the new stereogenic center in the cyclization product. Recent contributions of our group include the optimization of chirality transfer by using σ-donor ligands to gold, and applications in the total synthesis of natural products, e.g., of the β-carboline alkaloids (-)-isocyclocapitelline and (-)-isochrysotricine.

scholarly journals Enantioselective Synthesis of Angularly Substituted 1-Azabicylic Rings: Coupled Dynamic Kinetic Epimerization and Chirality Transfer

2013 ◽  
Vol 78 (19) ◽  
pp. 9929-9948 ◽  
Author(s):  
Zachary D. Aron ◽  
Tatsuya Ito ◽  
Tricia L. May ◽  
Larry E. Overman ◽  
Jocelyn Wang
Keyword(s):  
Enantioselective Synthesis ◽  
Chirality Transfer ◽  
Substituted 1

scholarly journals Trityl-Containing Alcohols—An Efficient Chirality Transmission Process from Inductor to the Stereodynamic Propeller and their Solid-State Structural Diversity

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 707 ◽  
Author(s):  
Sylwia Górczyńska ◽  
Aleksandra Brzdonkiewicz ◽  
Maciej Jelecki ◽  
Agnieszka Czapik ◽  
Bartosz Stasiak ◽  
...  
Keyword(s):  
Crystal Engineering ◽  
Electrostatic Interactions ◽  
Structural Diversity ◽  
Optically Active ◽  
Cascade Process ◽  
Chirality Transfer ◽  
Transmission Process ◽  
Close Proximity ◽  
Cotton Effects ◽  
Stereogenic Center

The cascade process of a dynamic chirality transmission from the permanent chirality center to the stereodynamic triphenylmethyl group has been studied for series of optically active trityl derivatives. The structural analysis, carried out with the use of complementary methods, enabled us to determine the mechanism of chirality transfer. The process of chirality transmission involves a set of weak but complementary electrostatic interactions. The induction of helicity in a trityl propeller is revealed by rising non-zero cotton effects in the area of trityl UV-absorption. The presence of an additional stereogenic center in close proximity to the trityl-containing stereogenic center significantly affects the sign and, to a lesser extent, magnitude of the respective cotton effects. Despite the bulkiness of the trityl, in the crystalline phase, the molecules under study strictly fill the space. In the crystal, molecules form aggregates stabilized by OH•••O hydrogen bonds. However, the presence of two trityl groups precludes formation of OH•••O hydrogen bonding. Additionally, the trityl group seems to be responsible for the formation of the solid solutions by e.g., racemates of trans- and cis-2-tritylcyclohexanol. Therefore, the trityl group acts as a supramolecular protective group, which in turn can be used in the crystal engineering.

α-Alkylation of (S)-Asparagine with Self-Regeneration of the Stereogenic Center:  Enantioselective Synthesis of α-Substituted Aspartic Acids1,2

1998 ◽  
Vol 63 (14) ◽  
pp. 4706-4710 ◽  
Author(s):  
Eusebio Juaristi ◽  
Heraclio López-Ruiz ◽  
Domingo Madrigal ◽  
Yara Ramírez-Quirós ◽  
Jaime Escalante
Keyword(s):  
Enantioselective Synthesis ◽  
Stereogenic Center

Chiral crotyl geminal bis(silane): a useful reagent for asymmetric Sakurai allylation by selective desilylation-enabled chirality transfer

2017 ◽  
Vol 53 (21) ◽  
pp. 3078-3081 ◽  
Author(s):  
Zhiwen Chu ◽  
Kai Wang ◽  
Lu Gao ◽  
Zhenlei Song
Keyword(s):  
Enantioselective Synthesis ◽  
Prins Cyclization ◽  
One Pot ◽  
Chirality Transfer

Enantioselective synthesis of SiMe3/SiPh2Me-substituted crotyl geminal bis(silane) has been developed. This compound is a useful reagent for Ph3C+B(C6F5)4−-catalyzed asymmetric Sakurai allylation and one-pot Sakurai allylation/Prins cyclization processes. Chemoselective desilylation of SiPh2Me leads to efficient chirality transfer.

Highly enantioselective Rh/chiral sulfur-olefin-catalyzed arylation of alkyl-substituted non-benzofused cyclic N-sulfonyl ketimines

2017 ◽  
Vol 4 (11) ◽  
pp. 2159-2162 ◽  
Author(s):  
Ming-Qing Liu ◽  
Tao Jiang ◽  
Wen-Wen Chen ◽  
Ming-Hua Xu
Keyword(s):  
Catalyst System ◽  
Enantioselective Synthesis ◽  
Effective Catalyst ◽  
Stereogenic Center

An effective catalyst system for the highly enantioselective synthesis of α-arylalkyl-substituted sulfamidates with a quaternary stereogenic center has been developed.

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