An approach to the synthesis of bruceantin. The synthesis of a tetracyclic intermediate

1989 ◽  
Vol 67 (12) ◽  
pp. 2237-2240 ◽  
Author(s):  
Sultan Darvesh ◽  
Andrew S. Grant ◽  
David I. Magee ◽  
Zdenek Valenta
Keyword(s):  
Sigmatropic Rearrangement ◽  
Terminal Acetylene ◽  
Chiral Centers ◽  
Oxygen Functionality

An intermediate (20) containing four of the five rings and seven of the ten chiral centers of bruceantin (1) was prepared. In a key reaction, 3-iodo-1-trimethylsilyl-5-hexen-1-yne (9) was found to add chemoselectively and stereoselectively to a dianion. The sequence also includes a selective attack by a sulfinate (17) on the terminal acetylene C-atom of the dianion of a keto acetylene, a concomitant cyclization in which the acetylene acts as an electrophile, and the use of the resulting allyl sulfoxide for the introduction of oxygen functionality by a reductive rearrangement. Keywords: bruceantin, sigmatropic rearrangement, stereoselective alkylation.

Self-Assembly of a Chiral Cubic Three-Connected Net from the High Symmetry Molecules C60 and SnI4

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava
Keyword(s):  
Organic Synthesis ◽  
Self Assembly ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
High Symmetry ◽  
Molecular Chirality ◽  
Chiral Materials ◽  
Self Assembled ◽  
Chiral Centers

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI4 molecules through spontaneous self-assembly. The SnI<sub>4</sub> tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi<sub>2</sub> type that is held together by van der Waals forces. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.

Three-Component [1+1+1] Cyclopropanation with Ruthenium(II)

2018 ◽  
Author(s):  
Tanner C. Jankins ◽  
Robert R. Fayzullin ◽  
Eugene Khaskin
Keyword(s):  
Quaternary Carbon ◽  
Poor Control ◽  
One Step ◽  
Synthetic Routes ◽  
Mechanistic Investigations ◽  
Chiral Centers ◽  
Metal Catalyzed ◽  
The Right ◽  
Substituted Cyclopropanes

We report a one-step, Ru(II)-catalyzed cyclopropanation reaction that is conceptually different from the previously reported protocols that include Corey-Chaykovsky, Simmons-Smith, and metal catalyzed carbene attack on olefins. Under the current protocol, various alcohols are transformed into sulfone substituted cyclopropanes with excellent isolated yields and diastereoselectivities. This new reaction forms highly congested cyclopropane products with three new C–C bonds, three or two new chiral centers and one new quaternary carbon center. 22 examples of isolated substrates are given. Previously reported synthetic routes for similar substrates are all multi-step, linear routes that proceed with overall low yields and poor control of stereochemistry. Experimental mechanistic investigations suggest initial metal-catalyzed dehydrogenation of the alcohol substrate and catalyst independent stepwise attack of two equivalents of sulfone on the aldehyde under basic conditions. While the Ru(II) is only responsible for the initial dehydrogenation step, the rate of aldehyde formation is crucial to maintaining the right balance of intermediates needed to afford the cyclopropane product.

Enantioselective Multi-Component Cyclopropane Synthesis Enabled by Cu-Catalyzed Cyclopropene Carbometallation with Organoboron Reagent

2018 ◽  
Author(s):  
Zhanyu Li ◽  
Mengru Zhang ◽  
Yu Zhang ◽  
Shuang Liu ◽  
Jinbo Zhao ◽  
...  
Keyword(s):  
Carbon Source ◽  
Stereoselective Synthesis ◽  
Organometallic Reagents ◽  
Preliminary Results ◽  
Quaternary Center ◽  
Chiral Centers ◽  
Substituted Cyclopropanes ◽  
Proof Of Principle

Deployment of organoboron in lieu of the strongly basic <br>organometallic reagents as carbon source in Cu-catalyzed <br>cyclopropene carbometallation opens unprecedented three-<br>component reactivity for stereoselective synthesis of poly-substituted cyclopropanes. A proof-of-principle demonstration of this novel carbometallation strategy is presented herein for a highly convergent access to poly-substituted aminocyclopropane framework via <br>carboamination. Preliminary results on asymmetric desymmetrization with commercial bisphosphine ligands attained high levels of enantioselection, offering a straightforward access to enantioenriched aminocyclopropanes bearing all-three chiral centers, including an all-carbon quaternary center. This strategy may underpin a host of novel synthetic protocols for poly-substituted cyclopropanes. <br>

scholarly journals Copper-Catalyzed Synthesis of Axially Chiral Biaryls with Diaryliodonium Salts as Arylation Reagents

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3223
Author(s):  
Ji-Wei Zhang ◽  
Shao-Hua Xiang ◽  
Shaoyu Li ◽  
Bin Tan
Keyword(s):  
Amino Alcohols ◽  
Sigmatropic Rearrangement ◽  
Synthetic Route ◽  
Mild Conditions ◽  
Good Substrate ◽  
Diaryliodonium Salts ◽  
Axially Chiral

NOBIN and BINAM derivatives harboring biaryl frameworks are recognized as a class of important atropisomers with versatile applications. Here, we present an efficient synthetic route to access such compounds through copper-catalyzed domino arylation of N-arylhydroxylamines or N-arylhydrazines with diaryliodonium salts and [3,3]-sigmatropic rearrangement. This reaction features mild conditions, good substrate compatibility, and excellent efficiency. The practicality of this protocol was further extended by the synthesis of biaryl amino alcohols.

An Umpolung Oxa-[2,3] Sigmatropic Rearrangement Employing Arynes for the Synthesis of Functionalized Enol Ethers

2021 ◽  
Author(s):  
Rahul N. Gaykar ◽  
Malini George ◽  
Avishek Guin ◽  
Subrata Bhattacharjee ◽  
Akkattu T. Biju
Keyword(s):  
Sigmatropic Rearrangement ◽  
Enol Ethers

Synthesis of oligomers including eight P-chiral centers and the construction of the 12-phosphacrown-4 skeleton

2005 ◽  
Vol 46 (41) ◽  
pp. 7011-7014 ◽  
Author(s):  
Yasuhiro Morisaki ◽  
Yuko Ouchi ◽  
Tatsuki Fukui ◽  
Kensuke Naka ◽  
Yoshiki Chujo
Keyword(s):  
Chiral Centers
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