28525-69-1Relevant academic research and scientific papers
Stereodivergent Nucleophilic Additions to Racemic β-Oxo Acid Derivatives: Fast Addition Outcompetes Stereoconvergence in the Archetypal Configurationally Unstable Electrophile
Crawford, Evan T.,De Jesús Cruz, Pedro,Johnson, Jeffrey S.,Liu, Shubin
supporting information, p. 16264 - 16273 (2021/10/21)
Additions of carbon nucleophiles to racemic α-stereogenic β-oxo acid derivatives that deliver enantiomerically enriched tertiary alcohols are valuable, but uncommon. This article describes stereodivergent Cu-catalyzed borylative cyclizations of racemic β-oxo acid derivatives bearing tethered pro-nucleophilic olefins to deliver highly functionalized cyclopentanols containing four contiguous stereogenic centers. The reported protocol is applicable to a range of β-oxo acid derivatives, and the diastereomeric products are readily isolable by typical chromatographic techniques. α-Stereogenic-β-keto esters are typically thought to have extreme or spontaneous configurational fragility, but mechanistic studies for this system reveal an unusual scenario wherein productive catalysis occurs on the same time scale as background substrate racemization and completely outcompetes on-cycle epimerization, even under the basic conditions of the reaction.
Organocatalytic, Organic Oxidant Promoted, Enamine C?H Oxidation/Cyclopropanation Reaction
Bond?i?, Aleksandra M.,Bond?i?, Bojan P.,D?ambaski, Zdravko,Kokotos, Christoforos G.,Triandafillidi, Ierasia
supporting information, p. 4002 - 4008 (2021/07/06)
Herein, we demonstrate that organic, single-electron oxidant in the presence of diarylprolinol silylether type catalyst serves as a tool for the transformation of electron-rich enamines to iminium ions. These iminium ions take part in a subsequent Michael-initiated ring-closure (MIRC) reaction with in situ present nucleophile giving rise to overall cyclopropanation reaction of saturated aldehydes. Stereodefined cyclopropanes are obtained in high yields and selectivities. This one-pot transformation represents the additional example of saturated aldehydes being used in the coupled one-pot processes. (Figure presented.).
Synthesis of Antitricyclic Morpholine Derivatives through Iodine(III)-Mediated Intramolecular Umpolung Cycloaddition of Olefins
Deng, Qingfu,Feng, Yangyang,Xiong, Ruimei,Xiong, Yan,Yang, Chenglin,Zhang, Xiaohui
, p. 4500 - 4506 (2020/04/09)
A (diacetoxyiodo)benzene-mediated intramolecular cycloaddition of olefins to construct tricyclic morpholines is presented. A series of substituted tricyclic morpholines were obtained in one-step simple operation under mild conditions, and the NMR studies
Bidentate auxiliary-directed alkenyl C-H allylation: Via exo-palladacycles: Synthesis of branched 1,4-dienes
Shen, Cong,Lu, Xiunan,Zhang, Jian,Ding, Liyuan,Sun, Yaling,Zhong, Guofu
, p. 13582 - 13585 (2019/11/14)
An alkenyl C-H allylation by an exo-palladacycle intermediate is demonstrated, employing unactivated (Z)-Alkenes and allyl carbonates. With the use of an 8-Aminoquinoline (AQ) derived amide as the directing group, the N,N-bidentate-chelation-Assisted C-H activation protocol proceeded under mild and oxidant-free conditions with excellent selectivity. The utility of this approach is demonstrated by the preparative scale, selective conversion of inseparable Z/E alkenes and ready removal of the amide auxiliary to provide the corresponding ester.
Enantioselective Organocatalytic Enamine C?H Oxidation/Diels- Alder Reaction
D?ambaski, Zdravko,Tzaras, Dimitrios-Ioannis,Lee, Sunggi,Kokotos, Christoforos G.,Bondzic, Bojan P.
supporting information, p. 1792 - 1797 (2019/02/25)
α,β-unsaturated aldehydes have been traditionally used in LUMO lowering asymmetric aminocatalysis (iminium catalysis), while the use of saturated aldehydes as substrates in this type of catalysis has been elusive, until recently. Herein, we demonstrate that organic, single-electron oxidants in the presence of diarylprolinol silylether type catalysts serve as effective tools for the transformation of electron rich enamines to iminium ions which partake in a subsequent Diels-Alder reaction. This enantioselective one-pot transformation represents the first example of saturated aldehydes being used in domino Diels-Alder reaction processes and demonstrates the power of this protocol for construction of stereo-defined chiral compounds and building blocks. (Figure presented.).
C(alkenyl)-H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis
Liu, Mingyu,Yang, Pusu,Karunananda, Malkanthi K.,Wang, Yanyan,Liu, Peng,Engle, Keary M.
supporting information, p. 5805 - 5813 (2018/05/14)
A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO2 as the stoichiometric oxidant or co-catalytic Co(OAc)2 and O2 (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.
Rapid Access to Thiolactone Derivatives through Radical-Mediated Acyl Thiol-Ene and Acyl Thiol-Yne Cyclization
McCourt, Ruairi O.,Dénès, Fabrice,Sanchez-Sanz, Goar,Scanlan, Eoin M.
supporting information, p. 2948 - 2951 (2018/05/28)
A new synthetic approach to thiolactones that employs an efficient acyl thiol-ene (ATE) or acyl thiol-yne (ATY) cyclization to convert unsaturated thiocarboxylic acid derivatives into thiolactones under very mild conditions is described. The high overall yields, fast kinetics, high diastereoselectivity, excellent regiocontrol, and broad substrate scope of these reaction processes render this a very useful approach for diversity-oriented synthesis and drug discovery efforts. A detailed computational rationale is provided for the observed regiocontrol.
trans-Cyclooctenes as Halolactonization Catalysts
Einaru, Shunsuke,Shitamichi, Kenta,Nagano, Tagui,Matsumoto, Akira,Asano, Keisuke,Matsubara, Seijiro
supporting information, p. 13863 - 13867 (2018/09/27)
The strained olefins in trans-cyclooctenes serve as efficient catalysts for halolactonizations, including bromolactonizations and iodolactonizations. The trans-cyclooctene framework is essential for excellent catalytic performance, and the substituents also play important roles in determining efficiency. These results are the first demonstration of catalysis by a trans-cyclooctene.
Total syntheses of surinone B, alatanones A–B, and trineurone A
Gundoju, Narayana Rao,Bokam, Ramesh,Yalavarthi, Nageswara Rao,Buddana, Sudheer Kumar,Prakasham,Ponnapalli, Mangala Gowri
, p. 1 - 8 (2018/04/30)
The total syntheses of four polyketides, surinone B (1), alatanones A–B (2–3), and trineurone A (4) were accomplished through an efficient and unified strategy via one-pot C-acylation reaction coupling 1,3-cyclohexadiones with EDC-activated acids under mild conditions. Alatanone A (2) was found to be a potent anti-microbial agent against Gram-positive and Gram-negative bacteria with MIC 31.25?μg/ml while alatanone B (3) was found to be a potent anti-fungal agent against Cladosporium cladosporioides with MIC 62.5?μg/ml compared to cycloheximide MIC 125?μg/ml. Our methodology allows performing kilogram scale of these scarce polyketides for the development of new antimicrobials.
Synthetic and Computational Study of Tin-Free Reductive Tandem Cyclizations of Neutral Aminyl Radicals
Sirinimal, Hansamali S.,Hebert, Sebastien P.,Samala, Ganesh,Chen, Heng,Rosenhauer, Gregory J.,Bernhard Schlegel,Stockdill, Jennifer L.
supporting information, p. 6340 - 6344 (2018/10/09)
5-exo, 5-exo Cyclizations of conformationally unbiased propargylic aminyl radicals proceed with excellent yield, chemoselectivity, and diastereoselectivity under tin-free reductive cyclization conditions, regardless of the electronic environments and intermediate radical stabilization resulting from various olefin substituents. These conditions avoid the need for slow addition of initiator and reductant. By contrast, analogous 6-exo, 5-exo cyclizations require substituents capable of intermediate radical stabilization to avoid premature reduction products. These experimental results are corroborated by computations that further establish the reactivity of these aminyl radicals upon exposure to tin-free cyclization conditions.
