scholarly journals Synthesis of Quaternary Carbon Stereogenic Centers by Diastereoselective Conjugate Addition of Boron-Stabilized Allylic Nucleophiles to Enones

2020 ◽  
Vol 142 (22) ◽  
pp. 9925-9931
Author(s):  
Michael Z. Liang ◽  
Simon J. Meek
Keyword(s):  
Conjugate Addition ◽  
Quaternary Carbon ◽  
Stereogenic Centers

scholarly journals N-Substituted tertiary and O-substituted quaternary carbon stereogenic centers by site-, diastereo- and enantioselective vinylogous Mannich reactions

2015 ◽  
Vol 56 (23) ◽  
pp. 3489-3493 ◽  
Author(s):  
Daniel L. Silverio ◽  
Peng Fu ◽  
Emma L. Carswell ◽  
Marc L. Snapper ◽  
Amir H. Hoveyda
Keyword(s):  
Quaternary Carbon ◽  
Mannich Reactions ◽  
Stereogenic Centers

Asymmetric tandem conjugate addition–protonation to forge chiral secondary C–O bonds for quaternary carbon stereocenters at the nonadjacent β-position

2017 ◽  
Vol 53 (54) ◽  
pp. 7493-7496 ◽  
Author(s):  
San-Ni Hong ◽  
Yang Liu ◽  
Richmond Lee ◽  
Zhiyong Jiang
Keyword(s):  
Conjugate Addition ◽  
Quaternary Carbon ◽  
Efficient Approach

The first asymmetric tandem conjugate addition–protonation to methylene 1,3-oxazolidine-2,4-diones has been developed, thus providing a direct and efficient approach to assemble chiral secondary C–O bonds for quaternary carbon stereocenters and thiols at the nonadjacent β-position.

Enantioselective Organocatalytic Construction of Carbocycles: The Nicolaou Synthesis of Biyouyanagin A

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Methyl Ether ◽  
Conjugate Addition ◽  
Unsaturated Aldehyde ◽  
Enantiomerically Pure ◽  
Intramolecular Alkylation ◽  
Stereogenic Centers ◽  
Chinese Academy Of Sciences ◽  
Academy Of Sciences ◽  
Polycyclic System ◽  
Selective Addition

One of the more powerful routes to enantiomerically-pure carbocycles is the desymmetrization of a prochiral ring. Karl Anker Jørgensen of Aarhus University has found (J. Am. Chem. Soc. 2007, 129, 441) that many cyclic β-ketoesters, including the vinylogous carbonate 1, can be homologated with 2 to the corresponding alkyne 3, in high ee. Sanzhong Luo of the Chinese Academy of Sciences, Beijing, and Jin-Pei Cheng, of the Chinese Academy of Sciences and Nankai University, have shown (J. Org. Chem. 2007, 72, 9350) that the catalyst 6 mediated the selective addition of 4-substituted cyclohexanones such as 4 to the nitroalkene 5, establishing three new stereogenic centers. Organocatalysts, alone or complexed with activating metals, have also been used to effect enantioselective ring construction. E. J. Corey of Harvard University has established (J. Am. Chem. Soc. 2007, 129, 12686) that the proline-derived complex 10 will mediate the 2 + 2 addition of a cyclic enol ether with an acrylate to give the cyclobutane 11. Further elaboration led to the cyclohexenone 12. Armando Córdova of Stockholm University has described (Tetrahedron Lett. 2007, 48, 5835) a novel route to cyclopentanones such as 16, via tandem conjugate addition/intramolecular alkylation. Professor Jørgensen has reported (Angew. Chem. Int. Ed . 2007, 46 , 9202) the double addition of 18 to the unsaturated aldehyde 17 to give 20. Earlier last year, Yujiro Hayashi of the Tokyo University of Science had shown (Angew. Chem. Int. Ed. 2007, 46, 4922) that the double addition of the inexpensive 21 to 5 could, depending on conditions, be directed selectively to 22, 23, or 24. As illustrated by the conversion of 8 to 13, organocatalysis can be used to effect the enantioselective construction of polycarbocyclic products. The initial ring prepared in enantiomerically-pure form by organocatalysis can also set the chirality of a polycyclic system. Professor Corey has reported (J. Am. Chem. Soc. 2007, 129, 10346) that Itsuno-Corey reduction of the prochiral diketone 25 led to the ketone 27. Cyclization followed by oxidation and reduction then delivered estrone methyl ether 28.

Enantioselective Construction of Alkylated Centers: The Maier Synthesis of Platencin

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Conjugate Addition ◽  
Unsaturated Ketone ◽  
West Virginia University ◽  
Aryl Iodide ◽  
Quaternary Centers ◽  
University Of New Mexico ◽  
Conjugate Reduction ◽  
Complementary Approach ◽  
Stereogenic Centers ◽  
The University

Jaesook Yun of Sungkyunkwan University devised (J. Org. Chem. 2009, 74, 4232) a method, based on conjugate addition to a cyano alkyne, for the preparation of nitriles such as 1 with high geometric control. Enantioselective conjugate reduction then delivered the doubly arylated stereogenic center of 2 in high ee. Pher G. Andersson of Uppsala University described (J. Am. Chem. Soc. 2009, 131, 8855) a similar approach to diarylated ternary stereogenic centers. Motomu Kanai and Masakatsu Shibasaki of the University of Tokyo developed (J. Am. Chem. Soc. 2009, 131, 3858) a complementary approach to dialkylated stereogenic centers based on enantioselective conjugate cyanation of α-methylene N-acylpyrroles such as 3. Cathleen M. Crudden of Queen’s University established (J. Am. Chem. Soc. 2009, 131, 5024) that a benzylic organoborane, prepared by enantioselective hydroboration of styrene, coupled with an aryl iodide such as 6 in good yield and with > 90% retention of ee. Kwunmin Chen of National Taiwan Normal University devised ( Adv. Synth. Cat. 2009, 351, 1273) an organocatalyst for the enantioselective Michael addition of an α,α,-dialkyl aldehyde such as 9 to a nitroalkene. Wenhu Duan of the East China University of Science and Technology and Wei Wang of the University of New Mexico together developed (Organic Lett. 2009, 11, 2864) an organocatalyst for the enantioselective addition of nitromethane 12 to an unsaturated ketone such as 11. Xiaodong Shi of West Virginia University found (Angew. Chem. Int. Ed. 2009, 48, 1279) that commercial diphenyl prolinol effectively promoted enantioselective conjugate addition of 15 to 14. Enantioselective methods for the construction of alkylated quaternary centers have also been put forward. Kin-ichi Tadano of Keio University devised (Tetrahedron Lett. 2009, 50, 1139) a glucose-derived chiral auxiliary that effectively directed the absolute sense of the alkylation of 17. Li Deng of Brandeis University reported (Tetrahedron 2009, 65, 3139) further details of his elegant Cinchona -mediated conjugate addition of 19 to 20. Francesca Marini of the Università degli Studi di Perugia extended (Adv. Synth. Cat. 2009, 351, 103) this approach to selenones, effecting, over two steps, enantioselective vinylation.

Copper-catalyzed asymmetric tandem borylative addition and aldol cyclization

2020 ◽  
Vol 7 (17) ◽  
pp. 2492-2498
Author(s):  
Bing Liu ◽  
Haile Qiu ◽  
Xiaofeng Chen ◽  
Wenbo Li ◽  
Junliang Zhang
Keyword(s):  
Conjugate Addition ◽  
Rapid Access ◽  
Stereogenic Centers ◽  
Aldol Cyclization

A highly enantioselective asymmetric copper-catalyzed tandem conjugate addition/aldol cyclization of electron-deficient olefins with B2pin2 was developed, which provided a rapid access to indanes bearing three consecutive chiral stereogenic centers.

Synthesis of the [7-5-5] tricyclic core of Daphniphyllum alkaloids

2018 ◽  
Vol 16 (19) ◽  
pp. 3556-3559 ◽  
Author(s):  
Yusuke Kitabayashi ◽  
Tohru Fukuyama ◽  
Satoshi Yokoshima
Keyword(s):  
Double Bond ◽  
Quaternary Carbon ◽  
Wittig Rearrangement ◽  
Stereogenic Centers ◽  
Tricyclic Core

The [7-5-5] tricyclic core of the Daphniphyllum alkaloids was constructed, featuring a Claisen-Ireland rearrangement to install the two contiguous stereogenic centers, E1cB elimination to form the tetrasubstituted C–C double bond, and a 2,3-Wittig rearrangement to construct the quaternary carbon.

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