61210-87-5Relevant academic research and scientific papers
Palladium(II)-Catalyzed Substituted Pyridine Synthesis from ?±,?-Unsaturated Oxime Ethers via a C-H Alkenylation/Aza-6?-Electrocyclization Approach
Yamada, Takahiro,Hashimoto, Yoshimitsu,Tanaka, Kosaku,Morita, Nobuyoshi,Tamura, Osamu
supporting information, p. 1659 - 1663 (2021/03/03)
An efficient synthetic method for multisubstituted pyridines from β-aryl-substituted α,β-unsaturated oxime ethers and alkenes via Pd-catalyzed C-H activation has been developed. Systematic optimization of catalyst ligands revealed that sterically hindered
Practical access to fluorescent 2,3-naphthalimide derivatives: Via didehydro-Diels-Alder reaction
Chen, Xia,Zhong, Cheng,Lu, Yuling,Yao, Meng,Guan, Zhenhua,Chen, Chunmei,Zhu, Hucheng,Luo, Zengwei,Zhang, Yonghui
supporting information, p. 5155 - 5158 (2021/05/31)
A practical and efficient approach for the synthesis of fluorescent 2,3-naphthalimide derivatives has been developed from readily available starting materials via an intramolecular didehydro-Diels-Alder reaction, which proceeded well under room temperature, exhibiting a wide substrate scope and good functional group tolerance. The practicability of this methodology has been verified by one-step synthesis of the environmentally sensitive fluorophore 6-DMN on a gram scale with a shorter time, fewer steps and less waste disposal, and without the utilization of toxic transition metals. The present experimental and computational studies support the crucial role of the propiolimide moiety in the transformation.
Sequential Two-Step Stereoselective Amination of Allylic Alcohols through the Combination of Laccases and Amine Transaminases
Albarrán-Velo, Jesús,Lavandera, Iván,Gotor-Fernández, Vicente
, p. 200 - 211 (2019/12/03)
A sequential two-step chemoenzymatic methodology for the stereoselective synthesis of (3E)-4-(het)arylbut-3-en-2-amines in a highly selective manner and under mild reaction conditions is described. The approach consists of oxidation of the corresponding racemic alcohol precursors by the use of a catalytic system made up of the laccase from Trametes versicolor and the oxy-radical TEMPO, followed by the asymmetric reductive bio-transamination of the corresponding ketone intermediates. Optimisation of the oxidation reaction, exhaustive amine transaminase screening for the bio-transaminations and the compatibility of the two enzymatic reactions were studied in depth in search of a design of a compatible sequential cascade. This synthetic strategy was successful and the combinations of enzymes displayed a broad substrate scope, with 16 chiral amines being obtained in moderate to good isolated yields (29–75 %) and with excellent enantiomeric excess values (94 to >99 %). Interestingly, both amine enantiomers can be achieved, depending on the selectivity of the amine transaminase employed in the system.
Scope and mechanism of a true organocatalytic beckmann rearrangement with a boronic acid/perfluoropinacol system under ambient conditions
Mo, Xiaobin,Morgan, Timothy D. R.,Ang, Hwee Ting,Hall, Dennis G.
supporting information, p. 5264 - 5271 (2018/04/24)
Catalytic activation of hydroxyl functionalities is of great interest for the production of pharmaceuticals and commodity chemicals. Here, 2-alkoxycarbonyl- and 2-phenoxycarbonyl-phenylboronic acid were identified as efficient catalysts for the direct and chemoselective activation of oxime N-OH bonds in the Beckmann rearrangement. This classical organic reaction provides a unique approach to prepare functionalized amide products that may be difficult to access using traditional amide coupling between carboxylic acids and amines. Using only 5 mol % of boronic acid catalyst and perfluoropinacol as an additive in a polar solvent mixture, the operationally simple protocol features mild conditions, a broad substrate scope, and a high functional group tolerance. A wide variety of diaryl, aryl-alkyl, heteroaryl-alkyl, and dialkyl oximes react under ambient conditions to afford high yields of amide products. Free alcohols, amides, carboxyesters, and many other functionalities are compatible with the reaction conditions. Investigations of the catalytic cycle revealed a novel boron-induced oxime transesterification providing an acyl oxime intermediate involved in a fully catalytic nonself-propagating Beckmann rearrangement mechanism. The acyl oxime intermediate was prepared independently and was subjected to the reaction conditions. It was found to be self-sufficient; it reacts rapidly, unimolecularly without the need for free oxime. A series of control experiments and 18O labeling studies support a true catalytic pathway involving an ionic transition structure with an active and essential role for the boronyl moiety in both steps of transesterification and rearrangement. According to 11B NMR spectroscopic studies, the additive perfluoropinacol provides a transient, electrophilic boronic ester that is thought to serve as an internal Lewis acid to activate the ortho-carboxyester and accelerate the initial, rate-limiting step of transesterification between the precatalyst and the oxime substrate.
Copper-catalyzed synthesis of thiazol-2-yl ethers from oxime acetates and xanthates under redox-neutral conditions
Zhu, Zhongzhi,Tang, Xiaodong,Cen, Jinghe,Li, Jianxiao,Wu, Wanqing,Jiang, Huanfeng
supporting information, p. 3767 - 3770 (2018/04/17)
A novel copper-catalyzed annulation of oxime acetates and xanthates for the synthesis of thiazol-2-yl ethers with remarkable regioselectivity has been developed. Various oxime acetates, whether derived from aryl ketones or alkyl ketones, or natural product cores are suitable for this conversion. Unique dihydrothiazoles were also obtained when both reaction sites were methine. Mechanistic studies indicated that imino copper(iii) intermediates were involved. In addition, this protocol proceeded under redox-neutral conditions and did not require additives or ligands.
Cu-Catalyzed Coupling of O-Acyl Oximes with Isatins: Domino Rearrangement Strategy for Direct Access to Quinoline-4-Carboxamides by C–N Bond Cleavage
Ramaraju, Andhavaram,Chouhan, Neeraj Kumar,Ravi, Owk,Sridhar, Balasubramanian,Bathula, Surendar Reddy
, p. 2963 - 2971 (2018/06/27)
A mild domino rearrangement strategy for the direct access to substituted quinoline-4-carboxamides has been developed. This copper-catalyzed coupling reaction of O-acyl oximes with isatins in the presence of molecular oxygen as the sole oxidizing agent proceeds through a ring expansion of the isatins through cleavage of the two C–N bonds.
Catalyst free synthesis of mono- and disubstituted pyrimidines from O-acyl oximes
Upare, Atul,Sathyanarayana, Pochampalli,Kore, Ranjith,Sharma, Komal,Bathula, Surendar Reddy
supporting information, p. 2430 - 2433 (2018/05/23)
Transition-metal or iodine catalyzed transformations of O-acyl oximes to various N-heterocycles are well established. Herein, we report a catalyst free, oxime carboxylate based, three-component condensation method to access mono- and disubstituted pyrimidines. A broad range of substituted pyrimidines were prepared in moderate to excellent yields. Control experiments reveal that in situ generated formamidine is the key intermediate.
Synthesis of Air- and Moisture-Stable, Storable Chiral Oxorhenium Complexes and Their Application as Catalysts for the Enantioselective Imine Reduction
Das, Braja Gopal,Nallagonda, Rajender,Dey, Dhananjay,Ghorai, Prasanta
supporting information, p. 12601 - 12605 (2015/09/01)
Air-/moisture-stable, crystalline, and storable chiral salicyloxazoline based oxorhenium(V) complexes have been synthesized and their catalytic application for the asymmetric reduction of ketimines using hydrosilane as hydride source is disclosed. A broad substrate scope, high yields, and excellent enantioselectivities (up to 99 %) are attained. Furthermore, the syntheses of enantiopure α-amino esters, γ- and δ-lactams, and isoindolinones have also been carried out using this methodology. Finally, the method has been applied to synthetic targets of pharmaceutical relevance, such as R-(+)-salsolidine and R-(+)-crispine A.
Copper-catalyzed rearrangement of N-aryl nitrones into epoxyketimines
Mo, Dong-Liang,Anderson, Laura L.
supporting information, p. 6722 - 6725 (2013/07/26)
Please pass the oxygen: A new method for the preparation of trans-α,β-epoxyketimines has been achieved through a copper-catalyzed rearrangement of (E)-α,β-unsaturated nitrones. The scope and tolerance of the method is evaluated and the synthetic utility of the products is demonstrated. The new transformation provides facile access to an unusual, densely functionalized intermediate that can be exploited for further synthetic application. Copyright
Pyridine synthesis from oximes and alkynes via rhodium(iii) catalysis: Cp* and Cpt provide complementary selectivity
Hyster, Todd K.,Rovis, Tomislav
supporting information; experimental part, p. 11846 - 11848 (2011/12/02)
The synthesis of pyridines from readily available α,β- unsaturated oximes and alkynes under mild conditions and low temperatures using Rh(iii) catalysis has been developed. It was found that the use of sterically different ligands allows for complementary selectivities to be achieved.
