28811-79-2Relevant academic research and scientific papers
Cobalt-Catalyzed Asymmetric 1,4-Reduction of β,β-Dialkyl α,β-Unsaturated Esters with PMHS
Lu, Dongpo,Lu, Peng,Lu, Zhan
supporting information, p. 4861 - 4864 (2021/09/22)
A cobalt-catalyzed asymmetric reduction of β,β-dialkyl α,β-unsaturated esters with polymethylhydrosiloxane (PMHS) was reported to deliver the corresponding esters containing a chiral trialkyl carbon center at β-position with up to 97 % yield and 98 % ee. The chiral tridentate ligand oxazoline iminopyridine (OIP) could perform well for the asymmetric reduction instead of chiral bidentate ligands. This operationally simple protocol shows a broad scope of substrates using one equivalent of readily available PMHS as a cheap and easy-to-handle reductive reagent.
An entry to non-racemic β-tertiary-β-amino alcohols, building blocks for the synthesis of aziridine, piperazine, and morpholine scaffolds
Narczyk, Aleksandra,Stecko, Sebastian
supporting information, p. 5972 - 5981 (2020/08/21)
A method for the preparation of enantiopure β-tert-amino alcohols bearing a tetrasubstituted C-stereocenter, as well as their conversion into selected medicinally privileged heterocyclic systems (morpholines, aziridines, piperazines) is reported. These co
Iridium-Catalyzed Asymmetric Isomerization of Primary Allylic Alcohols Using MaxPHOX Ligands: Experimental and Theoretical Study
Cabré, Albert,Gar?on, Martí,Gallen, Albert,Grisoni, Lorenzo,Grabulosa, Arnald,Verdaguer, Xavier,Riera, Antoni
, p. 4112 - 4120 (2020/07/04)
The asymmetric isomerization of primary allylic alcohols to chiral aldehydes using iridium-catalysts bearing P,N-MaxPHOX ligands has been studied. These catalysts can be fine-tuned as they present three different stereogenic centers to modulate both the reactivity and enantioselectivity of a family of different substrates. The experimental part is supported by a DFT study of the reaction mechanism, which provides new insights into the key steps of this transformation.
Enantioselective epoxidation of β,β-disubstituted enamides with a manganese catalyst and aqueous hydrogen peroxide
Clarasó, Carlota,Vicens, Laia,Polo, Alfonso,Costas, Miquel
supporting information, p. 2430 - 2435 (2019/03/29)
Enantioselective epoxidation of β,β-disubstituted enamides with aqueous hydrogen peroxide and a novel manganese catalyst is described. Epoxidation is stereospecific and proceeds fast under mild conditions. Amides are disclosed as key functional groups to enable high enantioselectivity.
Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes
Zimmermann, Birte M.,Kobosil, Sarah C. K.,Teichert, Johannes F.
supporting information, p. 2293 - 2296 (2019/02/27)
A simple and air-stable copper(i)/N-heterocyclic carbene complex enables the catalytic hydrogenation of enoates and enamides, hitherto unreactive substrates employing homogeneous copper catalysis and H2 as a terminal reducing agent. This atom economic transformation replaces commonly employed hydrosilanes and can also be carried out in an asymmetric fashion.
Transition-Metal-Free Formylation of Allylzinc Reagents Leading to α-Quaternary Aldehydes
Haraguchi, Ryosuke,Kusakabe, Akinori,Mizutani, Nakaba,Fukuzawa, Shin-Ichi
supporting information, p. 1613 - 1616 (2018/03/23)
The first example of formylation of allylzinc reagents using S-phenyl thioformate is presented. The reaction proceeded under mild conditions without any transition-metal catalyst, forming quaternary carbon centers with reactive functionalities, such as formyl and vinyl groups. Moreover, Barbier-type formylation of an allylic bromide with a sterically demanding thioformate was achieved. As a preliminary result, asymmetric formylation was conducted using a menthol-derived chiral thioformate.
Carbene-catalyzed enal γ-carbon addition to α-ketophosphonates for enantioselective access to bioactive 2-pyranylphosphonates
Sun, Jun,He, Fangcheng,Wang, Zhongyao,Pan, Dingwu,Zheng, Pengcheng,Mou, Chengli,Jin, Zhichao,Chi, Yonggui Robin
supporting information, p. 6040 - 6043 (2018/06/18)
A carbene-catalyzed enantioselective [4+2] cycloaddition reaction between α,β-unsaturated aldehydes and α-ketophosphonates is developed. The reaction affords chiral 2-pyranylphosphonates with excellent enantioselectivities. The optically enriched phosphonate products bear multiple functional groups, including unsaturated lactone and phosphonate moieties that often lead to unique bio-activities. Preliminary studies show that the products from our reactions exhibit anti-bacterial (X. oryzae pv. oryzae) and anti-viral (Tobacco Mosaic Virus) activities for potential use in plant protection.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Scope and Mechanistic Studies
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
supporting information, p. 17500 - 17507 (2017/12/15)
Although iminium catalysis has become an important tool in organic chemistry, its combination with supramolecular host systems has remained largely unexplored. We report the detailed investigations into the first example of iminium catalysis inside a supramolecular host. In the case of 1,4-reductions of α,β-unsaturated aldehydes, catalytic amounts of host are able to increase the enantiomeric excess of the products formed. Several control experiments were performed and provided strong evidence that the modulation of enantiomeric excess of the reaction product indeed stems from a reaction on the inside of the capsule. The origin of the increased enantioselectivity in the capsule was investigated. Furthermore, the substrate and nucleophile scope were studied. Kinetic investigations as well as the kinetic isotope effect measured confirmed that the hydride delivery to the substrate is the rate-determining step inside the capsule. The exploration of benzothiazolidines as alternative hydride sources revealed an unexpected substitution effect of the hydride source itself. The results presented confirm that the noncovalent combination of supramolecular hosts with iminium catalysis is opening up new exciting possibilities to increase enantioselectivity in challenging reactions.
Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
supporting information, p. 7698 - 7701 (2016/07/07)
The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
Enantioselective Hydrogenation of β,β-Disubstituted Unsaturated Carboxylic Acids under Base-Free Conditions
Yan, Qiaozhi,Kong, Duanyang,Zhao, Wei,Zi, Guofu,Hou, Guohua
, p. 2070 - 2077 (2016/03/15)
An additive-free enantioselective hydrogenation of β,β-disubstituted unsaturated carboxylic acids catalyzed by the Rh-(R,R)-f-spiroPhos complex has been developed. Under mild conditions, a wide scope of β,β-disubstituted unsaturated carboxylic acids were hydrogenated to the corresponding chiral carboxylic acids with excellent enantioselectivities (up to 99.3% ee). This methodology was also successfully applied to the synthesis of the pharmaceutical molecule indatraline.
