Stereo- and Regioselective Synthesis of Molecular Baskets

• Published in: Journal of organic chemistry Vol. 84; no. 7; pp. 4392 - 4401
• Main Authors: Gunther, Michael J, Pavlović, Radoslav Z, Fernandez, Joseph P, Zhiquan, Lei, Gallucci, Judith, Hadad, Christopher M, Badjić, Jovica D
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 05.04.2019; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Physical Sciences; Science & Technology; CATALYSIS; DIELS-ALDER REACTIONS; DIMENTHYL FUMARATE; OPTICAL-ROTATION; CYCLOPENTADIENE; ABSOLUTE-CONFIGURATIONS; CYCLOTRIMERIZATION
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.9b00330

We describe a stereoselective method for obtaining multigram quantities of molecular basket 1 syn in overall 11% yield, using inexpensive cyclopentadiene and diethyl fumarate as starting materials. First, an asymmetric synthesis of enantioenriched bromo­(trimethylstannyl)­alkene (−)-8 was accomplished by the stereoselective bromination of dibromonorbornene (+)-4 guided by anchimeric assistance and subsequent syn-exo-elimination of tetrabromonorbornane (−)-5a as the key steps. Subsequent Cu­(I)-catalyzed cyclotrimerization of (−)-8 was optimized to give 1 syn / anti in 85% yield and 1:1 ratio of diastereomers. Importantly, the results of our mechanistic experiments were in line with the cyclotrimerization occurring in a chain-type fashion with racemization of a Cu­(I) homochiral dimeric intermediate, reducing the stereoselectivity of the transformation. Enabled by more facile access to molecular baskets of type 1 syn , a range of recognition studies can now be completed for producing novel supramolecular catalysts, organophosphorus scavengers, and nanostructured materials.