132927-05-0Relevant articles and documents
Stereocontrolled Synthesis of Sulfonyl 2,5-Diaryltetrahydrofurans
Chang,Cheng
, p. 854 - 858 (2016)
BF3·OEt2-mediated stereocontrolled annulation of 4-alkenols affords sulfonyl 2,5-diaryltetrahydrofurans in good yields. The key synthetic route combines the facile stereoselective reduction of α-styryl-β-ketosulfones and an intramole
An Aliphatic Bischler-Napieralski Reaction: Dihydropyridones by Cyclocarbonylation of 3-Allylimidazolidin-4-ones
Amer, Mostafa M.,Olaizola, Olatz,Carter, Jennifer,Abas, Hossay,Clayden, Jonathan
, p. 253 - 256 (2020)
The N-chloroformylimidazolidinone derivative of enantiopure l-alanine was deprotonated to form an enolate and functionalized with a series of allylic halides. Treatment of the resulting carbamoyl chlorides with potassium iodide led to cyclization of the allylic substituent onto the carbonyl group in an intramolecular aliphatic Friedel-Crafts-type acylation that corresponds to an aliphatic Bischler-Napieralski reaction. The product 3,4-dihydropyridinones were amenable to further functionalization, and finally hydrolysis, to deliver a series of enantio-enriched pipecolic acid derivatives.
Role of Electron-Deficient Olefin Ligands in a Ni-Catalyzed Aziridine Cross-Coupling to Generate Quaternary Carbons
Estrada, Jesús G.,Williams, Wendy L.,Ting, Stephen I.,Doyle, Abigail G.
, p. 8928 - 8937 (2020)
We previously reported the development of an electron-deficient olefin (EDO) ligand, Fro-DO, that promotes the generation of quaternary carbon centers via Ni-catalyzed Csp3-Csp3 cross-coupling with aziridines. By contrast, electronically and structurally similar EDO ligands such as dimethyl fumarate and electron-deficient styrenes afford primarily β-hydride elimination side reactivity. Only a few catalyst systems have been identified that promote the formation of quaternary carbons via Ni-catalyzed Csp3-Csp3 cross-coupling. Although Fro-DO represents a promising ligand in this regard, the basis for its superior performance is not well understood. Here we describe a detailed mechanistic study of the aziridine cross-coupling reaction and the role of EDO ligands in facilitating Csp3-Csp3 bond formation. This analysis reveals that cross-coupling proceeds by a Ni0/II cycle with a NiII azametallacyclobutane catalyst resting state. Turnover-limiting C-C reductive elimination occurs from a spectroscopically observable NiII-dialkyl intermediate bound to the EDO. Computational analysis shows that Fro-DO accelerates turnover limiting reductive elimination via LUMO lowering. However, it is no more effective than dimethyl fumarate at reducing the barrier to Csp3-Csp3 reductive elimination. Instead, Fro-DO's unique reactivity arises from its ability to associate favorably to NiII intermediates. Natural bond order second-order perturbation theory analysis of the catalytically relevant NiII intermediate indicates that Fro-DO binds to NiII through an additional stabilizing donor-acceptor interaction between its sulfonyl group and NiII. Design of new ligands to evaluate this proposal supports this model and has led to the development of a new and tunable ligand framework.
Asymmetric [2+2] photocycloadditionviacharge transfer complex for the synthesis of tricyclic chiral ethers
Martínez-Gualda, Ana M.,Domingo-Legarda, Pablo,Rigotti, Thomas,Díaz-Tendero, Sergio,Fraile, Alberto,Alemán, José
supporting information, p. 3046 - 3049 (2021/03/29)
The asymmetric synthesis of chiral polycyclic ethers by an intramolecular [2+2] photocycloaddition is described. This process proceeded through a photocatalytically active iminium ion-based charge transfer (CT) complex under visible light irradiation. In this way a stereocontrolled [2+2] photocycloaddition is enabled leading to tricyclic products with good enantiomeric ratios.
Experimental and Computational Studies of Palladium-Catalyzed Spirocyclization via a Narasaka-Heck/C(sp3or sp2)-H Activation Cascade Reaction
Wei, Wan-Xu,Li, Yuke,Wen, Ya-Ting,Li, Ming,Li, Xue-Song,Wang, Cui-Tian,Liu, Hong-Chao,Xia, Yu,Zhang, Bo-Sheng,Jiao, Rui-Qiang,Liang, Yong-Min
supporting information, p. 7868 - 7875 (2021/05/27)
The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka-Heck/C(sp3 or sp2)-H activation reaction is reported here. The key step in this transformation is the activation of a δ-C-H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)-H activation step.
Pd-Catalyzed Asymmetric Acyl-Carbamoylation of an Alkene to Construct an α-Quaternary Chiral Cycloketone
Liu, Min,Wang, Xing,Guo, Ziqiong,Li, Hanyuan,Huang, Wei,Xu, Hui,Dai, Hui-Xiong
supporting information, p. 6299 - 6304 (2021/08/30)
Herein, we report the palladium-catalyzed asymmetric acyl-carbamoylation of an alkene by employing thioesters as the acyl electrophiles and t-BuNC as the carbamoyl reagent, affording an α-quaternary chiral cycloketone in synthetically useful yields with excellent enantioselectivity. The reaction proceeded via asymmetric 1,2-migratory insertions of acyl-Pd into alkenes and subsequent migratory insertion of isocyanides into C(sp3)-PdII. The product could be diversified to some valuable skeletons with retention of enantiopurity, demonstrating the synthetic utility of this protocol.
Visible-light-promoted radical alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester: Synthesis of oxazolines
Ding, Hao,Huang, Panyi,Jin, Can,Su, Weike,Sun, Bin,Yan, Zhiyang,Zhao, Haiyun
supporting information, (2021/10/29)
An efficient photocatalytic alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester has been developed. The transformation is taken advantage of alkyl radicals to attack allylic amide with the assist of inexpensive rose bengal as photocatalyst to prepare a series of alkyl substituted oxazolines in moderate to excellent yields. High regioselectivity, operational safety, mild conditions and excellent substrate generality give this protocol broad application prospects.
Synthesis of Six-Membered Spiro Azacyclic Oxindole Derivatives via a One-Pot Process of Umpolung Allylation/Aza-Prins Cyclization
Jang, Woo Cheol,Jung, Myeongjin,Ko, Haye Min
supporting information, p. 1510 - 1515 (2021/03/03)
An unprecedented synthetic approach involving umpolung allylation/aza-Prins cyclization of N-2,2,2-trifluoroethylisatin ketimines is described. The reactions proceed smoothly with allyl bromide in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, H2O, and trimethylsilyl bromide; this one-pot protocol allows access to six-membered spiro azacyclic oxindole derivatives in good to excellent yields. Notably, while the general aza-Prins cyclization involves amines and aldehydes, the present synthetic strategy represents the first aza-Prins cyclization that utilizes the umpolung property of N-2,2,2-trifluoroethylisatin ketimines.
Chiral Br?nsted Acid Catalyzed Dynamic Kinetic Asymmetric Hydroamination of Racemic Allenes and Asymmetric Hydroamination of Dienes
Lin, Jin-Shun,Li, Tao-Tao,Jiao, Guan-Yuan,Gu, Qiang-Shuai,Cheng, Jiang-Tao,Lv, Ling,Liu, Xin-Yuan
supporting information, p. 7092 - 7096 (2019/04/26)
The first highly efficient and practical chiral Br?nsted acid catalyzed dynamic kinetic asymmetric hydroamination (DyKAH) of racemic allenes and asymmetric hydroamination of unactivated dienes with both high E/Z selectivity and enantioselectivity are described herein. The transformation proceeds through a new catalytic asymmetric model involving a highly reactive π-allylic carbocationic intermediate, generated from racemic allenes or dienes through a proton transfer mediated by an activating/directing thiourea group. This method affords expedient access to structurally diverse enantioenriched, potentially bioactive alkenyl-containing aza-heterocycles and bicyclic aza-heterocycles.
Highly Enantioselective Iridium-Catalyzed Hydrogenation of 2-Aryl Allyl Phthalimides
Cabré, Albert,Romagnoli, Elia,Martínez-Balart, Pol,Verdaguer, Xavier,Riera, Antoni
supporting information, p. 9709 - 9713 (2019/11/19)
The iridium-catalyzed asymmetric hydrogenation of 2-aryl allyl phthalimides to afford enantioenriched β-aryl-β-methyl amines is presented. Recently developed Ir-MaxPHOX catalysts are used for this enantioselective transformation. The mild reaction conditions and the feasible removal of the phthalimido group makes this catalytic method easily scalable and of great interest to afford chiral amines. The importance of this new methodology is exemplified by the formal synthesis of (R)-Lorcaserin, OTS514, and enantiomerically enriched 3-methyl indolines.
