6006-75-3Relevant academic research and scientific papers
Asymmetric Desymmetrization of Oxetanes for the Synthesis of Chiral Tetrahydrothiophenes and Tetrahydroselenophenes
Zhang, Renwei,Guo, Wengang,Duan, Meng,Houk,Sun, Jianwei
, p. 18055 - 18060 (2019/11/13)
Chiral tetrahydrothiophenes and tetrahydroselenophenes are highly useful structural units. Described here is a new catalytic asymmetric approach for their synthesis. With a suitable chiral Br?nsted acid catalyst, an oxetane desymmetrization by a well-positioned internal sulfur or selenium nucleophile proceeded efficiently to generate all-carbon quaternary stereocenters with excellent enantioselectivities. Taming the sulfur and selenium nucleophile in the form of a thioester and selenoester, respectively, is crucial to the success of this work. This approach also allows the facile synthesis of chiral tetrahydrothiopyrans. Mechanistic studies, including DFT calculations, suggested an intramolecular acyl-transfer pathway. Utilities of the chiral products are also demonstrated.
Br?nsted Acid-Catalyzed Intramolecular Hydroarylation of β-Benzylstyrenes
Cai, Xiao,Keshavarz, Amir,Omaque, Justin D.,Stokes, Benjamin J.
supporting information, p. 2626 - 2629 (2017/05/24)
Using triphenylmethylium tetrakis(pentafluorophenyl)borate as a convenient Br?nsted acid precatalyst, β-(α,α-dimethylbenzyl)styrenes are shown to cyclize efficiently to afford a variety of new indanes that possess a benzylic quaternary center. The geminal dimethyl-containing quaternary center is proposed to be necessary to arm the substrate for cyclization through steric biasing.
Modular, catalytic enantioselective construction of quaternary carbon stereocenters by sequential cross-coupling reactions
Potter, Bowman,Edelstein, Emma K.,Morken, James P.
, p. 3286 - 3289 (2016/07/13)
The catalytic Suzuki-Miyaura cross-coupling with chiral γ,γ-disubstituted allylboronates in the presence of RuPhos ligand occurs with high regioselectivity and enantiospecificity, furnishing nonracemic compounds with quaternary centers. Mechanistic experiments suggest that the reaction occurs by transmetalation with allyl migration, followed by rapid reductive elimination.
A general stereoselective enamine mediated alkylation of α-substituted aldehydes
Gualandi, Andrea,Petruzziello, Diego,Emer, Enrico,Cozzi, Pier Giorgio
, p. 3614 - 3616 (2012/05/20)
We herein present a general enamine-mediated α-alkylation of α-substituted aldehydes with carbenium ions for the stereoselective construction of quaternary stereogenic centers.
Enantioselective construction of quaternary stereogenic centers from tertiary boronic esters: Methodology and applications
Sonawane, Ravindra P.,Jheengut, Vishal,Rabalakos, Constantinos,Larouche-Gauthier, Robin,Scott, Helen K.,Aggarwal, Varinder K.
supporting information; experimental part, p. 3760 - 3763 (2011/06/22)
Pin it down: A range of substrates that bear versatile functional groups with quaternary stereogenic centers have been prepared with very high enantioselectivity from tertiary boronic esters (see scheme; Cb=N,N-diisopropylcarbamoyl, pin=pinacolato). The preparation of allylboronic esters bearing contiguous quaternary and tertiary stereogenic centers, and applications to natural product synthesis are also reported.
Nickel-catalyzed enantioselective hydrovinylation of silyl-protected allylic alcohols: An efficient access to homoallylic alcohols with a chiral quaternary center
Zhang, Qi,Zhu, Shou-Fei,Cai, Yan,Wang, Li-Xin,Zhou, Qi-Lin
experimental part, p. 1899 - 1906 (2011/02/25)
Asymmetric hydrovinylation of silyl-protected allylic alcohols catalyzed by nickel complexes of chiral spiro phosphoramidite ligands was developed. A series of homoallylic alcohols with a chiral quaternary center were produced in high yields (up to 97%) and high enantioselectivities (up to 95% ee). The reaction provides an efficient method for preparing bifunctional compounds with a chiral quaternary carbon center.
Chiral primary amine mediated conjugate addition of branched aldehydes to vinyl sulfone: Asymmetric generation of quaternary carbon centers
Zhu, Qiang,Lu, Yixin
supporting information; experimental part, p. 2235 - 2237 (2010/07/09)
Novel l-threonine-derived bifunctional organic catalysts containing primary amine and sulfonamide groups were utilized to promote asymmetric conjugate addition of α,α-disubstitued aldehydes to 1,1-bis(benzenesulfonyl) ethylene. The adducts with quaternary
Metal-catalyzed ring-opening of alkylidenecyclopropanes: New access to building blocks with an acyclic quaternary stereogenic center
Simaan, Samah,Goldberg, Alexander F.G.,Rosset, Stephane,Marek, Ilan
supporting information; experimental part, p. 774 - 778 (2010/05/18)
A study was conducted to investigate metal-catalyzed ring-opening of alkylidenecyclopropanes (ACP). The investigations focused on developing this concept and to delineate the reactivity of exo-alkylidene moiety towards the metal-catalyzed hydroboration reaction. Methylene- and ACPs were subjected to pinacol borane (HBPin) in the presence of the Wilkinson catalyst at room temperature. HBPin was selected to conduct the investigations, as the reductive elimination to form the carbon-boron bond was slower than other boronate esters. The formation of the single boronate ester was rationalized through the oxidative addition of the catalyst into the H-B bond of HBPin that gave the corresponding metal hydride species. The metal hydride species added to the double bond of methylenecyclopropane (MCP) through a hydrometalation reaction to form the alkyl metal.
Asymmetric construction of quaternary carbon centers by regio- and enantiocontrolled allylzincation
Nakamura, Masaharu,Inoue, Toshihiro,Sato, Akihito,Nakamura, Eiichi
, p. 2193 - 2196 (2007/10/03)
(equation presented) An allylic zinc reagent bearing a chiral bisoxazoline ligand adds to a substituted cyclopropenone acetal to produce an optically active cyclopropanone acetal possessing a quaternary chiral center in high yield with 97.8-99.8% ee. The
Construction of a quaternary carbon center via cyclic sulfite
Nishimura, Nanae,Mitsunobu, Oyo
, p. 2945 - 2948 (2007/10/03)
Reaction of (S)-2-oxo-4-methyl-4-phenyl-1,3,2-dioxathiolane with triethylaluminum selectively took place at the tertiary carbinol center to give (R)-2-methyl-2-phenyl-1-butanol. Enhanced stereoselectivity was obtained in a nonpolar solvent. Similarly, a series of (S)-4,4-disubstituted-1,3,2- dioxathiolanes reacted with trimethylaluminum to afford the corresponding (R)-2-alkyl-2-phenyl-1-propanols in good yields. (C) 2000 Elsevier Science Ltd.
