- Regioselective iridium(I)-catalysed remote borylation of oxygenated naphthalenes
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We present our investigations into the regioselective borylation and halogenation of polyoxygenated naphthalene systems that are key precursors to dimeric pyranonaphthoquinone natural products. A variety of oxygenated naphthalenes were successfully borylated with pinacolborane in high yield and excellent regioselectivity using [Ir(COD)OMe]2 and di-tert-butylbipyridine (dtbpy). The boronates were also readily transformed into the corresponding halides, opening new avenues for the preparation of advanced Suzuki coupling substrates useful for the synthesis of natural products.
- Hume, Paul,Furkert, Daniel P.,Brimble, Margaret A.
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- A Synthetic Strategy for 2-Alkylchromanones: Fe(III)-Catalyzed A-Reductive Cross-Coupling of Unactivated Alkenes with Chromones
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A new synthetic approach for 2-alkylchromanones utilizing Fe (III)-catalyzed reductive cross-coupling of olefins with chromones has been developed. The reaction conditions are mild, and various substituted alkenes are applicable to the process. Moreover, control experiments were conducted, and a plausible mechanism is proposed.
- Chen, Xu-Ling,Dong, Yu,Tang, Lei,Zhang, Xiao-Mei,Wang, Ji-Yu
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- Two-Phase Reactions in Microdroplets without the Use of Phase-Transfer Catalysts
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Many important chemical transformations occur in two-phase reactions, which are widely used in chemical, pharmaceutical, and polymer manufacturing. We present an efficient method for performing two-phase reactions in microdroplets sheared by sheath gas without using a phase-transfer catalyst. This avoids disadvantages such as thermal instability, high cost, and, especially, the need to separate and recycle the catalysts. We show that various alcohols can be oxidized to the corresponding aldehydes and ketones within milliseconds in moderate to good yields (50–75 %). The scale-up of the present method was achieved at an isolated rate of 1.2 mg min?1 for the synthesis of 4-nitrobenzylaldehyde from 4-nitrobenzyl alcohol in the presence of sodium hypochlorite. The biphasic nature of this process, which avoids use of a phase-transfer catalyst, greatly enhances synthetic effectiveness.
- Yan, Xin,Cheng, Heyong,Zare, Richard N.
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- Photoredox-Catalyzed Simultaneous Olefin Hydrogenation and Alcohol Oxidation over Crystalline Porous Polymeric Carbon Nitride
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Booming of photocatalytic water splitting technology (PWST) opens a new avenue for the sustainable synthesis of high-value-added hydrogenated and oxidized fine chemicals, in which the design of efficient semiconductors for the in-situ and synergistic utilization of photogenerated redox centers are key roles. Herein, a porous polymeric carbon nitride (PPCN) with a crystalline backbone was constructed for visible light-induced photocatalytic hydrogen generation by photoexcited electrons, followed by in-situ utilization for olefin hydrogenation. Simultaneously, various alcohols were selectively transformed to valuable aldehydes or ketones by photoexcited holes. The porosity of PPCN provided it with a large surface area and a short transfer path for photogenerated carriers from the bulk to the surface, and the crystalline structure facilitated photogenerated charge transfer and separation, thus enhancing the overall photocatalytic performance. High reactivity and selectivity, good functionality tolerance, and broad reaction scope were achieved by this concerted photocatalysis system. The results contribute to the development of highly efficient semiconductor photocatalysts and synergistic redox reaction systems based on PWST for high-value-added fine chemical production.
- Qiu, Chuntian,Sun, Yangyang,Xu, Yangsen,Zhang, Bing,Zhang, Xu,Yu, Lei,Su, Chenliang
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p. 3344 - 3350
(2021/07/26)
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- Design, synthesis and preliminary bioactivity evaluation of bitopic benzopyranomorpholine analogues as selective dopamine D3 receptor ligands as anti-drug addiction therapeutic agents
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Three series of bitopic benzopyranomorpholine analogues were designed, synthesized, and evaluated as a novel class of selective ligands for the dopamine D3 receptor. Binding affinities of target compounds were determined using the method of radioligand binding assay. Most compounds demonstrated considerable binding affinities and selectivity for D3 receptor. Besides, the compounds were screened for their ability to alleviate withdrawal symptoms of opioid addiction in animal behavioral models. The results showed that compound 20h displayed nanomolar affinity for the D3R, and exhibited anti-drug addiction efficacy in the animal model of of naloxone-induced withdrawal symptoms in morphine-dependent mice.
- Cai, Jin,Chen, Xixi,Huang, Mingqi,Ji, Min,Wang, Yuhong
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- Acid activated montmorillonite K-10 mediated intramolecular acylation: Simple and convenient synthesis of 4-chromanones
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3-Aryloxyproionic acids undergo intramolecular cyclization in the presence of AA.Mont.K-10 in toluene under reflux for 30–45 min in good to excellent yields. Phenyl ring bearing various substituents at the ortho, meta, para positions undergo this cyclization reaction. This method involves simple work up and amenable for large scale preparations. The heterogeneous acid treated catalyst can be regenerated and used for up to three cycles with minimum loss of activity.
- Begum, Ayisha F.,Balasubramanian, Kalpattu K.,Shanmugasundaram, Bhagavathy
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- Synthesis and antimicrobial activity of 2-(4-phenyl-2h-chromen-3-yl)-1h-benzo[d]imidazole
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A new series of 4-phenyl-2H-chromene-3-benzimidazoles (8a-o) were synthesized by the condensation of 4-phenyl-2H-chromene-3- carbaldehyde with o-phenylene diamines. The products were purified through column chromatography and structures of these compounds were characterized by IR, 1H & 13C NMR and mass spectral data. All the final compounds were screened for their antimicrobial activity and their efficacy were matched with ciprofloxacin. Five compounds (8b, 8d, 8i, 8l and 8o) were found to be most effective compounds of this series and with activities improved than ciprofloxacin under the tested conditions.
- DASARI, RAMACHANDRAIAH,THALARI, GANGADHAR,YERRABELLY, JAYAPRAKASH RAO,CHITNENI, PRASAD RAO
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p. 1723 - 1728
(2021/07/31)
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- Design, Synthesis, and Antimicrobial Activity of (E)-4-Phenyl-2H-chromene-3-carbaldehyde O-[(1-Phenyl-1H-1,2,3-triazol-4-yl)methyl]oxime Derivatives
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Abstract: A new series of 1,4-disubstituted 1,2,3-triazole derivatives tethered to a2H-chromene scaffold have beensynthesized via a click reaction. The synthesized chromene–triazole conjugateswere screened for their antibacterial activity against E. coli, S. aureus, P. aeruginosa and B.subtilis, as well as for antifungal activity against A. niger and C. albicans. Among the 17 synthesized compounds, 6 derivativesshowed the best antimicrobial activity. Molecular docking studies of the titlecompounds with carotenoid dehydrosqualene synthase (PDB: 2ZCS) revealed dockingscores within the range 98.241–91.488 against 106.573 for the reference ligandCiprofloxacin and with lanosterol 14α-demethylase (CYP51; PDB ID: 5V5Z),103.672–96.917 against 110.839 for the reference ligand Voriconazole.
- Chittneni, P. Rao,Dasari, R.,Thalari, G.,Yerrabelly, J. Rao
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p. 1519 - 1532
(2021/10/26)
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- Oxidant-Free Selective Synthesis of Functionalized Chroman-4-ones from ortho -Hydroxyacetophenones under HOAc/DMSO Conditions
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A metal-free and oxidant-free acid-promoted DMSO activation and subsequent reaction is reported. In this protocol, two molecules of DMSO are activated by HOAc and serve as dual synthons which react with ortho-hydroxyacetophenones, affording 3-(methylthiomethyl)chroman-4-ones in moderate to good yields with high selectivity.
- Feng, Yuanyuan,Jiang, Tao-Shan,Li, Shuai,Shi, Xu,Wang, Anan
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- A novel one-pot synthesis of flavones
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In this paper, a one-pot facile route for the BiCl3/RuCl3-mediated synthesis of functionalized flavones is described, including: (i) intermolecularortho-acylation of substituted phenols with cinnamoyl chlorides, and (ii) intramolecular cyclodehydrogenation of the resultingo-hydroxychalcones. The reaction conditions are discussed herein.
- Chang, Meng-Yang,Tsai, Min-Chen,Lin, Chun-Yi
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p. 11655 - 11662
(2021/03/31)
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- Visible light mediated selective oxidation of alcohols and oxidative dehydrogenation of N-heterocycles using scalable and reusable La-doped NiWO4nanoparticles
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Visible light-mediated selective and efficient oxidation of various primary/secondary benzyl alcohols to aldehydes/ketones and oxidative dehydrogenation (ODH) of partially saturated heterocycles using a scalable and reusable heterogeneous photoredox catalyst in aqueous medium are described. A systematic study led to a selective synthesis of aldehydes under an argon atmosphere while the ODH of partially saturated heterocycles under an oxygen atmosphere resulted in very good to excellent yields. The methodology is atom economical and exhibits excellent tolerance towards various functional groups, and broad substrate scope. Furthermore, a one-pot procedure was developed for the sequential oxidation of benzyl alcohols and heteroaryl carbinols followed by the Pictet-Spengler cyclization and then aromatization to obtain the β-carbolines in high isolated yields. This methodology was found to be suitable for scale up and reusability. To the best of our knowledge, this is the first report on the oxidation of structurally diverse aryl carbinols and ODH of partially saturated N-heterocycles using a recyclable and heterogeneous photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Balasubramaniam, K. K.,Baskar, B.,Divya, P.,Mani Rahulan, K.,Rahman, Abdul,Sridhar, R.,Srinath, S.
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p. 5990 - 6007
(2021/08/24)
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- Chemoselective Hydrosilylation of the α,β-Site Double Bond in α,β- And α,β,γ,δ-Unsaturated Ketones Catalyzed by Macrosteric Borane Promoted by Hexafluoro-2-propanol
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The B(C6F5)3-catalyzed chemoselective hydrosilylation of α,β- and α,β,γ,δ-unsaturated ketones into the corresponding non-symmetric ketones in mild reaction conditions is developed. Nearly 55 substrates including those bearing reducible functional groups such as alkynyl, alkenyl, cyano, and aromatic heterocycles are chemoselectively hydrosilylated in good to excellent yields. Isotope-labeling studies revealed that hexafluoro-2-propanol also served as a hydrogen source in the process.
- Zhan, Xiao-Yu,Zhang, Hua,Dong, Yu,Yang, Jian,He, Shuai,Shi, Zhi-Chuan,Tang, Lei,Wang, Ji-Yu
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p. 6578 - 6592
(2020/07/17)
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- Diboron-Mediated Rhodium-Catalysed Transfer Hydrogenation of Alkenes and Carbonyls
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A diboron-mediated rhodium-catalysed transfer hydrogenation system using water as the hydrogen donor is developed. In addition to a series of alkenes with good functional group tolerance, this rhodium-based catalytic system also effectively reduces aldehydes and ketones. A plausible mechanism involving the RhI-catalysed hydrogen generation and Rh0-catalysed hydrogenation is proposed for the reaction.
- Lin, Xiao,Wang, Yuhan,Hu, Yan,Zhu, Wanjiang,Dou, Xiaowei
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supporting information
p. 1046 - 1049
(2020/02/25)
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- Synthesis and anti-inflammatory activity of 2-oxo-2H-chromenyl and 2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates
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Cycloaddition reaction of 4-chloro-2-oxo-2H-chromene-3-carbaldehydes (3a-g) and 4-chloro-2H-chromene-3-carbaldehydes (7a-h) with activated alkynes (4a-b) provided the 2-oxo-2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates (5a-n) and 2H-chromenyl-5-oxo-2,5-dihydrofuran-3-carboxylates (8a-p). All the prepared compounds were screened for anti-inflammatory activity. In vitro anti-inflammatory activity data demonstrated that the compounds 5g, 5i, 5k-l and 8f are effective among the tested compounds against TNF-α (1.108 ± 0.002, 0.423 ± 0.022, 0.047 ± 0.001, 0.070 ± 0.002 and 0.142 ± 0.001 μM) in comparison with standard compound Prednisolone (0.033 ± 0.002 μM). Based on in vitro results, three compounds (5i, 5k and 8f) have been selected for in vivo experiments and these compounds are identified as better compounds with respect to anti-inflammatory activity in LPS induced mice model. Compound 5i was identified as potent and showed significant reduction in TNF-α and IL-6.
- Bhimapaka, China Raju,Karri, Shailaja,Kuncha, Madhusudana,Kurma, Siva Hariprasad,Sistla, Ramakrishna
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- Mild Deprotection of Dithioacetals by TMSCl/NaI Association in CH3CN
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A mild process using a combination of TMSCl and NaI in acetonitrile is used to regenerate carbonyl compounds from a variety of dithiane and dithiolane derivatives. This easy to handle and inexpensive protocol is also efficient to deprotect oxygenated and mixed acetals as 1,3-dioxanes, 1,3-dioxolanes and 1,3-oxathianes quantitatively. As a possible extension of this method, it was also shown that nitrogenated substrates such as hydrazones, N-tosylhydrazones, and ketimines reacted well under these conditions to give the expected ketones in high yields. The methodology proposed herein is a good alternative to the existing methods since it does not use metals, oxidants, reducing agents, acidic or basic media, and keto-products were obtained in high to excellent yields.
- Yao, Yunxin,Zhao, Guangkuan,Hamze, Abdallah,Alami, Mouad,Provot, Olivier
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p. 5775 - 5779
(2020/08/17)
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- Strigolactone analogues derived from dihydroflavonoids as potent seed germinators for the broomrapes
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The broomrapes (Orobanche and Phelipanche spp.) and witchweeds (Striga spp.) are a class of parasitic weeds, which are distributed widely in the tropical, subtropical, and temperate areas of the globe. Since they have completely consistent lifecycles with the host plants, it is difficult to control them selectively through using the conventional herbicides. Inducing suicidal germination of these weed seeds by small molecular signaling agents proved to be a promising strategy for the management of parasitic weeds. As a class of naturally occurring terpenoid metabolites, strigolactones (SLs) show significant biological activities including stimulation germination of weed seeds, inhibition of shoot-branching, and so on. However, the widespread application of these natural SLs is greatly limited by their extremely low natural abundance and complex molecular structures. Design and synthesis of the simplified analogues as natural SLs alternatives provide a viable avenue for the efficient control of these parasitic weeds. We herein disclose the development of a novel class of SLs analogues derived from dihydroflavonoids as potent seed germinators of parasitic weeds. It was shown that one of them displayed a higher potential toward the seed germination of the broomrapes than the positive control GR24. The structure-activity relationship of these SLs analogues was further validated on the basis of the binding affinity experiment to strigolactone receptor protein HTL7 by using a YLG fluorescent probe method.
- Chen, Fangjie,Jin, Zhong,Kang, Yunyao,Pang, Zhili,Xu, Niuniu,Xu, Xiaohua
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p. 11077 - 11087
(2020/11/10)
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- Palladium Complexes Bearing Chiral bis(NHC) Chelating Ligands on a Spiro Scaffold: Synthesis, Characterization, and Their Application in the Oxidative Kinetic Resolution of Secondary Alcohols
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A series of chiral bis-N-heterocyclic carbene ligands H2[(S)-1a-d]X2 (X = Br, I) on a spiro scaffold and their palladium complexes (S)-2a-d and (S)-3a,b were prepared and applied in the enantioselective oxidative kinetic resolution of secondary alcohols. The corresponding alcohols can be obtained in high yields with moderate to excellent ee values.
- Zhang, Dao,Yu, Jueqin
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p. 605 - 613
(2020/02/13)
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- Manganese/Copper Co-catalyzed Electrochemical Wacker-Tsuji-Type Oxidation of Aryl-Substituted Alkenes
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A manganese/copper co-catalyzed electrochemical Wacker-Tsuji-type oxidation of aryl-substituted alkenes has been developed. The process involves the use of 5 mol % MnBr2 and 7.5 mol % CuCl2, in 4:1 acetonitrile/water in an undivided cell at 60 °C, with 2.8 V constant applied potential. α-Aryl ketones are formed in moderate to excellent yields, with the advantages of avoidance of palladium as a catalyst and any external chemical oxidant in an easily operated, cost-effective procedure.
- Lai, Junshan,Pericàs, Miquel A.
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supporting information
p. 7338 - 7342
(2020/10/02)
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- A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for aerobic oxidation of alcohols
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A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for the aerobic oxidation of alcohols has been developed for the first time, and the photoredox aerobic oxidation of secondary and primary alcohols provided the corresponding ketones and carboxylic acids, respectively, in high to excellent yields.
- Zhu, Xianjin,Liu, Can,Liu, Yong,Yang, Haijun,Fu, Hua
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p. 12443 - 12446
(2020/10/30)
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- SYNTHESIS OF HYPERVALENT IODINE REAGENTS WITH DIOXYGEN
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Methods of synthesis of hypervalent iodine reagents and methods for oxidation of organic compounds are disclosed.
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Paragraph 0114-0117; 0136-0137
(2019/01/15)
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- Two-Phase Reactions in Microdroplets
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Improved two phase chemical reactions (liquid-liquid or liquid-gas) are provided by forming microdroplets of either or both liquid reagents and configuring the reaction as a collision between the microdroplet reagent and the other reagent. We have found that this approach can provide high reaction yields in short times (1 s) without the use of a phase transfer catalyst.
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Paragraph 0052; 0055
(2019/12/01)
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- Benzyne-Mediated Nonconcerted Pathway toward Synthesis of Sterically Crowded [5]- and [7]Oxahelicenoids, Stereochemical and Theoretical Studies, and Optical Resolution of Helicenoids
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Synthesis of [5]- and [7]oxahelicenoids via Diels-Alder reaction of sterically crowded bichromenes with benzyne is presented. Studies carried out on Diels-Alder addition product establish the unusual preference for a stepwise mechanism over the concerted reaction pathway. This high yielding general synthetic protocol affords unexpected anti cycloadducts [5]- and [7]oxahelicenoids, as confirmed by crystallographic analysis. To rationalize these intriguing antiaddition products, the reaction mechanism was elucidated by means of DFT analysis. Additionally, hydroxy-functionalized [7]oxahelicenoid has been resolved in its optically pure forms.
- Gawade, Prashant M.,Khose, Vaibhav N.,Badani, Purav M.,Hasan, Mohammed,Kaabel, Sandra,Mobin, Shaikh M.,Borovkov, Victor,Karnik, Anil V.
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- Benzyne-Mediated Nonconcerted Pathway toward Synthesis of Sterically Crowded [5]- And [7]Oxahelicenoids, Stereochemical and Theoretical Studies, and Optical Resolution of Helicenoids
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Synthesis of [5]- and [7]oxahelicenoids via Diels-Alder reaction of sterically crowded bichromenes with benzyne is presented. Studies carried out on Diels-Alder addition product establish the unusual preference for a stepwise mechanism over the concerted reaction pathway. This high yielding general synthetic protocol affords unexpected anti cycloadducts [5]- and [7]oxahelicenoids, as confirmed by crystallographic analysis. To rationalize these intriguing antiaddition products, the reaction mechanism was elucidated by means of DFT analysis. Additionally, hydroxy-functionalized [7]oxahelicenoid has been resolved in its optically pure forms.
- Badani, Purav M.,Borovkov, Victor,Gawade, Prashant M.,Hasan, Mohammed,Kaabel, Sandra,Karnik, Anil V.,Khose, Vaibhav N.,Mobin, Shaikh M.
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p. 860 - 868
(2021/08/24)
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- Synthesis of Flavanones via Palladium(II)-Catalyzed One-Pot β-Arylation of Chromanones with Arylboronic Acids
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A total of 47 flavanones were expediently synthesized via one-pot β-arylation of chromanones, a class of simple ketones possessing chemically unactivated β sites, with arylboronic acids via tandem palladium(II) catalysis. This reaction provides a novel route to various flavanones, including natural products such as naringenin trimethyl ether, in yields up to 92percent.
- Cho, Yang Yil,Jang, Hyu Jeong,Kim, Dong Hwan,Kim, Nam Yong,Kim, Nam-Jung,Kim, Young Min,Lee, Soo Jin,Lee, Yong Sup,Park, Boyoung Y.,Son, Seung Hwan,Yoo, Hyung-Seok
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supporting information
p. 10012 - 10023
(2019/08/30)
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- Chroman-4-one hydrazones derivatives: synthesis, characterization, and in vitro and in vivo antileishmanial effects
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In searching for better therapeutic alternatives to treat cutaneous leishmaniasis (CL), this study aimed to obtain and evaluate the efficacy and toxicity of new chroman-4-one hydrazones derivatives. Compounds were prepared and characterized, and then transformed into hydrazonas for molecular optimization. Their cytotoxicity was tested in different cell types using an in vitro MTT assay and the efficacy was evaluated using an in vitro macrophage intracellular amastigotes of Leishmania (Viannia) panamensis and L. (V) braziliensis by flow cytometry. The therapeutic effect of two formulations of chroman-4-one hydrazones on the CL induced by L. (V) braziliensis in golden hamsters was determined according to the size of lesions after treatment. The effect of these compounds in the production of inflammatory mediators and cell migration was also determined by in vitro assays using human fibroblasts models. Neither cytotoxicity nor genotoxicity was observed. The benzoic acid hydrazone derivative 2-(2,3-dihydro-4H-1-benzopyran-4-ylidene) hydrazide (4), produced a higher percentage of clinical cures, followed by benzoic acid, 2-(2,3-dihydro-4H-1-benzothiopyran-4-ylidene) hydrazide (3), while benzoic acid, 2-(2,3-dihydro-1,1-dioxide-4H-1-benzothiopyran-4-ylidene) hydrazide (5) and 4-pyridinecarboxylic acid, 2-(4H-1-benzopyran-4-ylidene) hydrazide (6) caused a poor therapeutic response. The compound 4 also showed an effect in the inflammatory and fibroblast migration processes. In conclusion, this is the first report of antileishmanial activity combined with inflammatory and wound healing properties. Results obtained here suggest that this strategy could be a good alternative for development of new drugs for the treatment of CL.
- Upegui, Yulieth,Rios, Karina,Qui?ones, Wiston,Echeverri, Fernando,Archbold, Rosendo,Murillo, Javier D.,Torres, Fernando,Escobar, Gustavo,Vélez, Iván D.,Robledo, Sara M.
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p. 2184 - 2199
(2019/11/03)
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- Redox-Neutral Coupling between Two C(sp3)?H Bonds Enabled by 1,4-Palladium Shift for the Synthesis of Fused Heterocycles
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The intramolecular coupling of two C(sp3)?H bonds to forge a C(sp3)?C(sp3) bond is enabled by 1,4-Pd shift from a trisubstituted aryl bromide. Contrary to most C(sp3)?C(sp3) cross-dehydrogenative couplings, this reaction operates under redox-neutral conditions, with the C?Br bond acting as an internal oxidant. Furthermore, it allows the coupling between two moderately acidic primary or secondary C?H bonds, which are adjacent to an oxygen or nitrogen atom on one side, and benzylic or adjacent to a carbonyl group on the other side. A variety of valuable fused heterocycles were obtained from easily accessible ortho-bromophenol and aniline precursors. The second C?H bond cleavage was successfully replaced with carbonyl insertion to generate other types of C(sp3)-C(sp3) bonds.
- Rocaboy, Ronan,Anastasiou, Ioannis,Baudoin, Olivier
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p. 14625 - 14628
(2019/09/16)
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- Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A
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The construction of the biologically interesting chromone skeleton was realized by PhIO-mediated dehydrogenation of chromanones under mild conditions. Interestingly, this method also found application in the synthesis of the naturally occurring frutinone A.
- Li, Qiao,Zhuang, Chen,Wang, Donghua,Zhang, Wei,Jia, Rongxuan,Sun, Fengxia,Zhang, Yilin,Du, Yunfei
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supporting information
p. 2958 - 2965
(2020/01/08)
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- Transfer-dehydrogenation of secondary alcohols catalyzed by manganese NNN-pincer complexes
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Novel catalytic systems based on pentacarbonylmanganese bromide and stable NNN-pincer ligands are presented for the transfer-dehydrogenation of secondary alcohols to give the corresponding ketones in good to excellent isolated yields. Best results are obtained using di-picolylamine derivatives as ligands and acetone as an inexpensive hydrogen acceptor. Besides high activity for benzylic substrates, aliphatic alcohols, as well as steroid derivatives, are readily oxidized in the presence of the optimal phosphorus-free catalyst.
- Budweg, Svenja,Junge, Kathrin,Beller, Matthias
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supporting information
p. 14143 - 14146
(2019/12/02)
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- Iron–PNP-Pincer-Catalyzed Transfer Dehydrogenation of Secondary Alcohols
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The well-defined iron PNP pincer complex catalyst [Fe(H)(BH4)(CO)(HN{CH2CH2P(iPr)2}2] was used for the catalytic dehydrogenation of secondary alcohols to give the corresponding ketones. Using acetone as inexpensive hydrogen acceptor enables the oxidation with good to excellent yields. DFT computations indicate an outer-sphere mechanism and support the importance of an acceptor to achieve this transformation under milder conditions.
- Budweg, Svenja,Wei, Zhihong,Jiao, Haijun,Junge, Kathrin,Beller, Matthias
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- Hydrogen bond donor solvents enabled metal and halogen-free Friedel–Crafts acylations with virtually no waste stream
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We have developed a metal and halogen-free Friedel–Crafts acylation protocol with virtually no waste stream generation. We propose a hydrogen bonding donor solvent will form a hydrogen bonding network and may provide significant rate enhancement for Friedel–Crafts reactions. Trifluoroacetic acid is one of the strongest H-bond donor solvents, which is also volatile and can be easily recovered by distillation without need for reaction workup. Our protocol is a ‘green’ Friedel–Crafts acylation process: 1) the catalyst can be recovered and reused; 2) using halogen free starting material (carboxylic acids anhydride or carboxylic acids); 3) no need for aqueous reaction work-up; 4) minimum or no waste steam generation.
- Liu, Guangchang,Xu, Bo
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supporting information
p. 869 - 872
(2018/02/09)
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- Thiyl radical promoted chemo- and regioselective oxidation of CC bonds using molecular oxygen: Via iron catalysis
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The first example of the thiyl radical promoted ligand-free iron-catalyzed oxidative cleavage of alkenes using molecular oxygen (1 atm) has been developed. The reaction proceeds under mild reaction conditions with high efficiency and high chemo- and regioselectivity. It features a broad substrate scope and excellent functional group compatibility, enabling facile access to valuable molecules for application in medicinal chemistry. Preliminary mechanistic studies reveal that a vital intermediate dioxetane might be involved in the reaction and a thiyl radical plays a synergistic role in facilitating the selective oxidation of the CC bond.
- Xiong, Baojian,Zeng, Xiaoqin,Geng, Shasha,Chen, Shuo,He, Yun,Feng, Zhang
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supporting information
p. 4521 - 4527
(2018/10/17)
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- Earth-Abundant Mixed-Metal Catalysts for Hydrocarbon Oxygenation
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The oxygenation of aliphatic and aromatic hydrocarbons using earth-abundant Fe and Cu catalysts and "green" oxidants such as hydrogen peroxide is becoming increasingly important to atom-economical chemical processing. In light of this, we describe that dinuclear CuII complexes of pyrrolic Schiff-base macrocycles, in combination with ferric chloride (FeCl3), catalyze the oxygenation of π-activated benzylic substrates with hydroperoxide oxidants at room temperature and low loadings, representing a novel design in oxidation catalysis. Mass spectrometry and extended X-ray absorption fine structure analysis indicate that a cooperative action between CuII and FeIII occurs, most likely because of the interaction of FeCl3 or FeCl4- with the dinuclear CuII macrocycle. Voltammetric measurements highlight a modulation of both CuII and FeIII redox potentials in this adduct, but electron paramagnetic resonance spectroscopy indicates that any Cu-Fe intermetallic interaction is weak. High ketone/alcohol product ratios, a small reaction constant (Hammett analysis), and small kinetic isotope effect for H-atom abstraction point toward a free-radical reaction. However, the lack of reactivity with cyclohexane, oxidation of 9,10-dihydroanthracene, oxygenation by the hydroperoxide MPPH (radical mechanistic probe), and oxygenation in dinitrogen-purge experiments indicate a metal-based reaction. Through detailed reaction monitoring and associated kinetic modeling, a network of oxidation pathways is proposed that includes "well-disguised" radical chemistry via the formation of metal-associated radical intermediates.
- Pankhurst, James R.,Curcio, Massimiliano,Sproules, Stephen,Lloyd-Jones, Guy C.,Love, Jason B.
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supporting information
p. 5915 - 5928
(2018/05/28)
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- Metal-Free catalyst for visible-light-induced oxidation of unactivated alcohols using Air/Oxygen as an oxidant
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9-Fluorenone acts as a metal-free and additive-free photocatalyst for the selective oxidation of primary and secondary alcohols under visible light. With this photocatalyst, a plethora of alcohols such as aliphatic, heteroaromatic, aromatic, and alicyclic compounds has been converted to the corresponding carbonyl compounds using air/oxygen as an oxidant. In addition to these, several steroids have been oxidized to the corresponding carbonyl compounds. Detailed mechanistic studies have also been achieved to determine the role of the oxidant and the photocatalyst for this oxidation.
- Schilling, Waldemar,Riemer, Daniel,Zhang, Yu,Hatami, Nareh,Das, Shoubhik
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p. 5425 - 5430
(2018/05/15)
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- Oxidation Catalysis by an Aerobically Generated Dess–Martin Periodinane Analogue
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Hypervalent iodine(V) reagents, such as Dess–Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to generate these reagents from dioxygen (O2) would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. In this work, aerobic oxidation of iodobenzenes is coupled with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. The developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.
- Maity, Asim,Hyun, Sung-Min,Wortman, Alan K.,Powers, David C.
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supporting information
p. 7205 - 7209
(2018/05/29)
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- Hydrated ferric sulfate-catalyzed reactions of indole with aldehydes, ketones, cyclic ketones, and chromanones: Synthesis of bisindoles and trisindoles
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Hydrated ferric sulfate [Fe2(SO4)3·xH2O] has been found to be an efficient catalyst for condensation of bisindoles or trisindoles with aliphatic or aryl aldehydes and ketones including methyl and ethyl-alkyl ketones, methyl aryl ketones, cyclic ketones, and 4-chromanones in 19–96% yields. Trisindoles and 2,2'-alkylidenebisindoles were obtained from indole-3-carbaldehydes or 3-methylindole in 72–84% yields. A total of 43 substrates was employed, giving 33 bisindoles, 3 trisindoles, and one 2:2 product; seventeen of these are new. The best results were obtained from heating ethanolic suspensions, with Fe2(SO4)3·xH2O loaded at 60 mg per mmol of electrophiles. The reaction times were typically 1–4 h, while hindered electrophiles required 8–24 h. These conditions were strong enough to promote 2:1 condensation of indole with substrates without forming higher-order byproducts, with few exceptions. This strategy features tolerance by the catalyst of a wide range of functional groups, readily available starting materials, simple operation, mild reaction conditions, and is environmentally friendly.
- Noland, Wayland E.,Kumar, Honnaiah Vijay,Flick, Grant C.,Aspros, Cole L.,Yoon, Jong Hyeon,Wilt, Andre C.,Dehkordi, Nasim,Thao, Sheng,Schneerer, Andrew K.,Gao, Siming,Tritch, Kenneth J.
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p. 3913 - 3922
(2017/06/13)
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- Synthesis, characterization, and antimicrobial activity of novel substituted 2H-chromenyl acrylates
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The present study deals with conventional Witting olefination of 2H-chromene-3-carbaldehydes with stabilized ylide in the presence of dichloromethane to afford (2E)-ethyl-3-(4-chloro-2H-chromen-3-yl) acrylate derivatives. All the products were found to have E-geometry at C=C bond. The synthesized compounds were characterized by spectral data such as IR, 1H NMR and MS. Compounds were screened for antimicrobial activity against strains of gram positive, gram negative bacterial and fungal strains. All compounds showed good antibacterial and antifungal activity.
- Subhashini,Ravi,Cherupally,China Raju,Reddy,Bee
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p. 2900 - 2905
(2017/03/22)
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- Acceptorless Dehydrogenative Oxidation of Secondary Alcohols Catalysed by Cp*IrIII–NHC Complexes
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A series of new IrIIIcomplexes with carbene ligands that contain a range of benzyl wingtip groups have been prepared and fully characterised by NMR spectroscopy, HRMS, elemental analysis and X-ray diffraction. All the complexes were active in the acceptorless dehydrogenation of alcohol substrates in 2,2,2-trifluoroethanol to give the corresponding carbonyl compounds. The most active complex bore an electron-rich carbene ligand; this complex was used to catalyse the highly efficient and chemoselective dehydrogenation of a wide range of secondary alcohols to their respective ketones, with turnover numbers up to 1660. Mechanistic studies suggested that the turnover of the dehydrogenation reaction is limited by the H2-formation step.
- Gülcemal, Süleyman,Gülcemal, Derya,Whitehead, George F. S.,Xiao, Jianliang
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supporting information
p. 10513 - 10522
(2016/07/21)
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- Ruthenium-catalyzed conjugate hydrogenation of ?±,?2-enones by in situ generated dihydrogen from paraformaldehyde and water
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Notwithstanding that the highly selective hydrogenation of ?±,?2-enones to allylic alcohols can be realized by using Noyori's Ru bifunctional system, the selective reduction of the C=C bonds in ?±,?2-enones without touching the C=O bonds still lacks a general, simple, and efficient procedure. Ruthenium-catalyzed conjugate hydrogenation of various ?±,?2-enones to saturated ketones with high selectivity was investigated. The most important feature of this procedure was that hydrogen in situ generated from paraformaldehyde (or formalin) and water was employed as the reductant.
- Li, Wanfang,Wu, Xiao-Feng
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supporting information
p. 331 - 335
(2015/03/05)
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- Intramolecular Friedel-Crafts Acylation Reaction Promoted by 1,1,1,3,3,3-Hexafluoro-2-propanol
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Simple dissolution of an arylalkyl acid chloride in 1,1,1,3,3,3-hexafluoro-2-propanol promotes an intramolecular Friedel-Crafts acylation without additional catalysts or reagents. This reaction is operationally trivial in both execution and product isolation (only requiring concentration followed by purification) and accommodates a broad range of substrates. Preliminary studies that bear upon potential reaction mechanisms are reported.
- Motiwala, Hashim F.,Vekariya, Rakesh H.,Aubé, Jeffrey
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p. 5484 - 5487
(2015/11/18)
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- Desulfonylative Methenylation of β-Keto Sulfones
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A one-step strategy for the synthesis of α-methenyl ketones from β-keto sufones is reported. Success of the methodology is elaborated for the synthesis of chromanones and isoflavanones in one-step.
- Pandey, Ganesh,Vaitla, Janakiram
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p. 4890 - 4893
(2015/10/12)
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- Highly efficient oxidation of alcohols catalyzed by a porphyrin-inspired manganese complex
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A novel strategy for catalytic oxidation of a variety of benzylic, allylic, propargylic, and aliphatic alcohols to the corresponding aldehydes or ketones by an in situ formed porphyrin-inspired manganese complex in excellent yields (up to 99%) has been successfully developed.
- Dai, Wen,Lv, Ying,Wang, Lianyue,Shang, Sensen,Chen, Bo,Li, Guosong,Gao, Shuang
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supporting information
p. 11268 - 11271
(2015/07/07)
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- FeCl3 and ether mediated direct intramolecular acylation of esters and their application in efficient preparation of xanthone and chromone derivatives
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The direct intramolecular acylation of esters was developed by using the combined system of FeCl3 with Cl2CHOCH3. This unique cooperative system offered a new and efficient approach to biologically important xanthone and chromone derivatives with regioselectivity. Examples were reported, and control experiments were carried out to examine the effect of the benzyl esters and Cl2CHOCH3.
- Jiang, Neng,Li, Su-Yi,Xie, Sai-Sai,Yao, Hequan,Sun, Hongbin,Wang, Xiao-Bing,Kong, Ling-Yi
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p. 63632 - 63641
(2015/02/19)
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- Synthesis, enantiomeric separation and docking studies of spiropiperidine analogues as ligands of the nociceptin/orphanin FQ receptor
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A series of triazospirodecanone derivatives were synthesized as potential NOP ligands. 8-(Chroman-4-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one (4) and its 5-fluoro analogue (18) proved to be active as agonists with EC50 values in the submicromolar range. Single enantiomers of compound 4 were separated and tested as NOP agonists; the eutomer R-(+)-4 showed a pEC 50 of 7.34. Finally docking studies were performed on the NOP receptor to identify the most significant stereospecific interactions.
- Battisti, Umberto M.,Corrado, Sandra,Sorbi, Claudia,Cornia, Andrea,Tait, Annalisa,Malfacini, Davide,Cerlesi, Maria Camilla,Calò, Girolamo,Brasili, Livio
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p. 973 - 983
(2014/07/08)
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- Cobalt(II) phthalocyanine covalently anchored to cellulose as a recoverable and efficient catalyst for the aerobic oxidation of alkyl arenes and alcohols
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Cobalt(II) phthalocyanine covalently immobilized on cellulose as a heterogeneous catalyst was synthesized and characterized. The catalyst showed good catalytic activity for the aerobic oxidation of alkyl arenes and alcohols under relatively mild reaction conditions. The catalyst can readily be recovered from the reaction mixture and reused for several runs without significant decrease in catalytic activity.
- Shaabani, Ahmad,Keshipour, Sajjad,Hamidzad, Mona,Shaabani, Shabnam
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p. 494 - 499
(2014/12/10)
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- Aerobic oxidation of alcohols by using a completely metal-free catalytic system
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A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H +(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H 2SO4) were recovered as ammonium salts. A metal-free reaction system of air/NH4NO3(cat)/TEMPO (cat)/H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl, alkyl and allyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Copyright
- Prebil, Rok,Stavber, Gaj,Stavber, Stojan
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supporting information
p. 395 - 402
(2014/01/23)
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- Aerobic Oxidation of Alcohols by Using a Completely Metal-Free Catalytic System
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A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H2SO4) were recovered as ammonium salts.
- Prebil, Rok,Stavber, Gaj,Stavber, Stojan
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supporting information
p. 395 - 402
(2015/10/05)
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- Design and synthesis of HIV-1 protease inhibitors for a long-acting injectable drug application
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The design and synthesis of novel HIV-1 protease inhibitors (PIs) (1-22), which display high potency against HIV-1 wild-type and multi-PI-resistant HIV-mutant clinical isolates, is described. Lead optimization was initiated from compound 1, a Phe-Phe hydroxyethylene peptidomimetic PI, and was directed towards the discovery of new PIs suitable for a long-acting (LA) injectable drug application. Introducing a heterocyclic 6-methoxy-3-pyridinyl or a 6-(dimethylamino)-3-pyridinyl moiety (R3) at the para-position of the P1′ benzyl fragment generated compounds with antiviral potency in the low single digit nanomolar range. Halogenation or alkylation of the metabolic hot spots on the various aromatic rings resulted in PIs with high stability against degradation in human liver microsomes and low plasma clearance in rats. Replacing the chromanolamine moiety (R1) in the P2 protease binding site by a cyclopentanolamine or a cyclohexanolamine derivative provided a series of high clearance PIs (16-22) with EC50s on wild-type HIV-1 in the range of 0.8-1.8 nM. PIs 18 and 22, formulated as nanosuspensions, showed gradual but sustained and complete release from the injection site over two months in rats, and were therefore identified as interesting candidates for a LA injectable drug application for treating HIV/AIDS.
- Kesteleyn, Bart,Amssoms, Katie,Schepens, Wim,Hache, Geerwin,Verschueren, Wim,Van De Vreken, Wim,Rombauts, Klara,Meurs, Greet,Sterkens, Patrick,Stoops, Bart,Baert, Lieven,Austin, Nigel,Wegner, J?rg,Masungi, Chantal,Dierynck, Inge,Lundgren, Stina,J?nsson, Daniel,Parkes, Kevin,Kalayanov, Genadiy,Wallberg, Hans,Rosenquist, ?sa,Samuelsson, Bertil,Van Emelen, Kristof,Thuring, Jan Willem
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p. 310 - 317
(2013/02/25)
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- Highly efficient Cu(I)-catalyzed oxidation of alcohols to ketones and aldehydes with diaziridinone
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A novel and efficient Cu(I)-catalyzed oxidation of alcohols has been achieved with di-tert-butyldiaziridinone as the oxidant under mild conditions. A wide variety of primary and secondary alcohols with various functional groups can be oxidized to aldehydes and ketones in high yields. The reaction proceeds under neutral conditions making it compatible with acid- or base-sensitive substrates, and it is amenable to gram scale.
- Zhu, Yingguang,Zhao, Baoguo,Shi, Yian
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supporting information
p. 992 - 995
(2013/04/10)
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