5498-74-8Relevant academic research and scientific papers
Photocatalyzed Multiple Additions of Amines to α,β-Unsaturated Esters and Nitriles
Das, Suresh,Kumar, J. S. Dileep,Thomas, K. George,Shivaramayya, K.,George, M. V.
, p. 628 - 634 (1994)
Photoelectron-transfer-catalyzed intermolecular carbon-carbon bond formation of primary, secondary, and tertiary amines with α,β-unsaturated esters and nitriles using photosensitizers such as anthraquinone, acridone, and dicyanoanthracene has been investigated.The addition of α-aminoalkyl radicals, generated via photoelectron-transfer processes, to olefinic substrates and the subsequent 1,5-hydrogen abstraction reactions of the amine-olefin adduct radicals lead to a number of interesting multiple-olefin-added products.The adducts of the primary and secondary amines with α,β-unsaturated esters undergo further cyclizations to give spiro and cyclic lactams, respectively.
Highly Robust Iron Catalyst System for Intramolecular C(sp3)?H Amidation Leading to γ-Lactams
Kweon, Jeonguk,Chang, Sukbok
supporting information, p. 2909 - 2914 (2020/12/11)
Disclosed here is the use of an iron catalyst system for an intramolecular C?H amidation toward γ-lactam synthesis from dioxazolone precursors. (Phthalocyanine)FeIIICl was found to catalyze this cyclization with extremely high turnover numbers of up to 47 000 under mild and aerobic conditions. On the basis of experimental and computational mechanistic studies, the reaction is suggested to proceed by a stepwise radical pathway involving fast hydrogen atom abstraction followed by radical rebound. A plausible origin for the high turnover numbers along with air-compatibility is also rationalized.
Photocatalytic α-Tertiary Amine Synthesis via C?H Alkylation of Unmasked Primary Amines
Alder, Catherine M.,Ballantyne, George,Cresswell, Alexander J.,Cunningham, William B.,Edwards, Lee J.,Grayson, Matthew N.,Kinsella, Anna G.,McKay, Blandine S. J.,Mules, Tom,Ryder, Alison S. H.,Turner-Dore, Jacob
, p. 14986 - 14991 (2020/06/20)
A practical, catalytic entry to α,α,α-trisubstituted (α-tertiary) primary amines by C?H functionalisation has long been recognised as a critical gap in the synthetic toolbox. We report a simple and scalable solution to this problem that does not require any in situ protection of the amino group and proceeds with 100 percent atom-economy. Our strategy, which uses an organic photocatalyst in combination with azide ion as a hydrogen atom transfer (HAT) catalyst, provides a direct synthesis of α-tertiary amines, or their corresponding γ-lactams. We anticipate that this methodology will inspire new retrosynthetic disconnections for substituted amine derivatives in organic synthesis, and particularly for challenging α-tertiary primary amines.
Synthesis of Lactams via Ir-Catalyzed C-H Amidation Involving Ir-Nitrene Intermediates
Li, Xiaoxun,Liu, Jitian,Tang, Weiping,Wang, Shuojin,Ye, Wenjing,Zheng, Junrong
, (2020/03/19)
x-membered lactams were synthesized via either an amidation of sp3 C-H bonds or an electrophilic substitution of arenes via Ir-nitrene intermediates. With the employment of a readily available iridium catalyst in dichloromethane or hexafluoro-2-propanol, a wide range of lactams were synthesized in good to excellent yields with high selectivity.
Tuning Triplet Energy Transfer of Hydroxamates as the Nitrene Precursor for Intramolecular C(sp3)-H Amidation
Chang, Sukbok,Jung, Hoimin,Keum, Hyeyun,Kweon, Jeonguk
supporting information, p. 5811 - 5818 (2020/04/10)
Reported herein is the design of a photosensitization strategy to generate triplet nitrenes and its applicability for the intramolecular C-H amidation reactions. Substrate optimization by tuning physical organic parameters according to the proposed energy transfer pathway led us to identify hydroxamates as a convenient nitrene precursor. While more classical nitrene sources, representatively organic azides, were ineffective under the current photosensitization conditions, hydroxamates, which are readily available from alcohols or carboxylic acids, are highly efficient in accessing synthetically valuable 2-oxazolidinones and γ-lactams by visible light. Mechanism studies supported our working hypothesis that the energy transfer path is mainly operative.
Non- C2-Symmetric Chiral-at-Ruthenium Catalyst for Highly Efficient Enantioselective Intramolecular C(sp3)-H Amidation
Zhou, Zijun,Chen, Shuming,Hong, Yubiao,Winterling, Erik,Tan, Yuqi,Hemming, Marcel,Harms, Klaus,Houk,Meggers, Eric
, p. 19048 - 19057 (2019/12/04)
A new class of chiral ruthenium catalysts is introduced in which ruthenium is cyclometalated by two 7-methyl-1,7-phenanthrolinium heterocycles, resulting in chelating pyridylidene remote N-heterocyclic carbene ligands (rNHCs). The overall chirality results from a stereogenic metal center featuring either a or Δabsolute configuration. This work features the importance of the relative metal-centered stereochemistry. Only the non-C2-symmetric chiral-at-ruthenium complexes display unprecedented catalytic activity for the intramolecular C(sp3)-H amidation of 1,4,2-dioxazol-5-ones to provide chiral -lactams with up to 99:1 er and catalyst loadings down to 0.005 mol % (up to 11 ?200 TON), while the C2-symmetric diastereomer favors an undesired Curtius-type rearrangement. DFT calculations elucidate the origins of the superior C-H amidation reactivity displayed by the non-C2-symmetric catalysts compared to related C2-symmetric counterparts.
Synthetic Utility of N-Benzoyloxyamides as an Alternative Precursor of Acylnitrenoids for γ-Lactam Formation
Huh, Soohee,Hong, Seung Youn,Chang, Sukbok
, p. 2808 - 2812 (2019/04/17)
Described herein is the development of a new entry of acylnitrenoid precursors for γ-lactam synthesis via an intramolecular C-H amidation reaction. Upon Ir catalysis, N-benzoyloxyamides serve as efficient substrates to afford 5-membered amides. Mechanistic studies revealed that the generation of a putative Ir-carbonylnitrenoid via N-O bond cleavage is facilitated by the chelation of countercations. This protocol offers a convenient and step-economic route to γ-lactams starting from the corresponding carboxylic acids.
Harnessing Secondary Coordination Sphere Interactions That Enable the Selective Amidation of Benzylic C-H Bonds
Jung, Hoimin,Schrader, Malte,Kim, Dongwook,Baik, Mu-Hyun,Park, Yoonsu,Chang, Sukbok
supporting information, p. 15356 - 15366 (2019/10/22)
Engineering site-selectivity is highly desirable especially in C-H functionalization reactions. We report a new catalyst platform that is highly selective for the amidation of benzylic C-H bonds controlled by π-πinteractions in the secondary coordination sphere. Mechanistic understanding of the previously developed iridium catalysts that showed poor regioselectivity gave rise to the recognition that the π-cloud of an aromatic fragment on the substrate can act as a formal directing group through an attractive noncovalent interaction with the bidentate ligand of the catalyst. On the basis of this mechanism-driven strategy, we developed a cationic (ν5-C5H5)Ru(II) catalyst with a neutral polypyridyl ligand to obtain record-setting benzylic selectivity in an intramolecular C-H lactamization in the presence of tertiary C-H bonds at the same distance. Experimental and computational techniques were integrated to identify the origin of this unprecedented benzylic selectivity, and robust linear free energy relationship between solvent polarity index and the measured site-selectivity was found to clearly corroborate that the solvophobic effect drives the selectivity. Generality of the reaction scope and applicability toward versatile γ-lactam synthesis were demonstrated.
Selective formation of γ-lactams via C-H amidation enabled by tailored iridium catalysts
Hong, Seung Youn,Park, Yoonsu,Hwang, Yeongyu,Kim, Yeong Bum,Baik, Mu-Hyun,Chang, Sukbok
, p. 1016 - 1021 (2018/03/09)
Intramolecular insertion of met al nitrenes into carbon-hydrogen bonds to form γ-lactam rings has traditionally been hindered by competing isocyanate formation. We report the application of theory and mechanism studies to optimize a class of pentamethylcyclopentadienyl iridium(III) catalysts for suppression of this competing pathway. Modulation of the stereoelectronic properties of the auxiliary bidentate ligands to be more electron-donating was suggested by density functional theory calculations to lower the C-H insertion barrier favoring the desired reaction. These catalysts transform a wide range of 1,4,2-dioxazol-5-ones, carbonylnitrene precursors easily accessible from carboxylic acids, into the corresponding γ-lactams via sp3 and sp2 C-H amidation with exceptional selectivity. The power of this method was further demonstrated by the successful late-stage functionalization of amino acid derivatives and other bioactive molecules.
Straightforward and effective synthesis of γ-aminobutyric acid transporter subtype 2-selective acyl-substituted azaspiro[4.5]decanes
Ma, Xiaofeng,Lubin, Hodney,Ioja, Eniko,Kékesi, Orsolya,Simon, ágnes,Apáti, ágota,Orbán, Tamás I.,Héja, László,Kardos, Julianna,Markó, István E.
supporting information, p. 417 - 423 (2016/01/09)
Supply of major metabolites such as γ-aminobutyric acid (GABA), β-alanine and taurine is an essential instrument that shapes signalling, proper cell functioning and survival in the brain and peripheral organs. This background motivates the synthesis of no
