- Manganese(III)-Promoted Double Carbonylation of Anilines Toward α-Ketoamides Synthesis
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Employing anilines as nucleophiles in double carbonylation is a longstanding challenge. In this communication, a Mn(III)-promoted double carbonylation of alkylborates or Hantzsch esters with anilines toward the synthesis of α-ketoamides has been developed. By using easily available potassium alkyltrifluoroborates or Hantzsch esters as the starting material, and cheap and non-toxic Mn(OAc)3 ? 2H2O as the promotor, a broad range of alkyl α-ketoamide derivatives were synthesized in moderate to good yields with excellent selectivity. (Figure presented.).
- Chen, Bo,Kuai, Chang-Sheng,Xu, Jian-Xing,Wu, Xiao-Feng
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supporting information
p. 487 - 492
(2021/12/06)
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- Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**
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Ethynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl-substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX-mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C?H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.
- Amos, Stephanie G. E.,Cavalli, Diana,Le Vaillant, Franck,Waser, Jerome
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supporting information
p. 23827 - 23834
(2021/09/25)
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- Intermolecular Radical Addition to Ketoacids Enabled by Boron Activation
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The intermolecular radical addition to the carbonyl group is difficult due to the facile fragmentation of the resulting alkoxyl radical. To date, the intermolecular radical addition to ketones, a valuable approach to construct quaternary carbon centers, remains a formidable synthetic challenge. Here, we report the first visible-light-induced intermolecular alkyl boronic acid addition to α-ketoacids enabled by the Lewis acid activation. The in situ boron complex formation is confirmed by various spectroscopic measurements and mechanistic probing experiments, which facilitates various alkyl boronic acid addition to the carbonyl group and prevents the cleavage of the newly formed C-C bond. Diversely substituted lactates can be synthesized from readily available alkyl boronic acids and ketoacids at room temperature merely under visible light irradiation, without any additional reagent. This boron activation approach can be extended to alkyl dihydropyridines as radical precursors with external boron reagents for primary, secondary, and tertiary alkyl radical additions. The pharmaceutically useful anticholinergic precursors are easily scaled up in multigrams under metal-free conditions in flow reactors.
- Xie, Shasha,Li, Defang,Huang, Hanchu,Zhang, Fuyuan,Chen, Yiyun
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supporting information
p. 16237 - 16242
(2019/10/14)
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- Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis
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The alkynylbenziodoxole derivatives are recently developed alkynylation reagents in organic synthesis, which demonstrate excellent radical alkynylation reactivity in photoredox catalysis reactions. Herein we report the synthesis of alkynylbenziodoxole derivatives with difluoro, monofluoro, monomethoxy, and dimethoxy substitution on the benziodoxole moiety, and investigated their radical alkynylation reactivity for the first time. A series of mechanistic experiments were conducted to study the radical acceptor and oxidative quencher reactivity of alkynylbenziodoxoles, in which unsubstituted alkynylbenziodoxoles played balancing roles in both processes, while electron-rich benziodoxole derivatives demonstrate synthetic advantages in some cases.
- Pan, Yue,Jia, Kunfang,Chen, Yali,Chen, Yiyun
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supporting information
p. 1215 - 1221
(2018/06/13)
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- Preparation of alkyltrifluoroborates via Matteson Hydroboration Method
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An efficient one-pot method for synthesis of simple alkyltrifluoroborate salts has been developed. Alkyldichloroboranes, prepared by the Matteson Hydroboration Method using in situ generated HBCl2, were esterified with 2-propanol, treated with
- Zillman, David J.,Cole, Thomas E.
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p. 159 - 165
(2018/04/05)
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- Selective C?N Borylation of Alkyl Amines Promoted by Lewis Base
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An efficient method for the metal-free deaminative borylation of alkylamines, using bis(catecholato)diboron as the boron source, to directly synthesize various alkyl potassium trifluoroborate salts is introduced. The key to this high reactivity is the utilization of pyridinium salt activated alkylamines, with a catalytic amount of a bipyridine-type Lewis base as a promoter. This transformation shows good functional-group compatibility (e.g., it is unimpeded by the presence of a ketone, indole, internal alkene, or unactivated alkyl chloride) and can serve as a powerful synthetic tool for borylation of amine groups in complex compounds. Mechanistic experiments and computations suggest a mechanism in which the Lewis base activated B2cat2 unit intercepts an alkyl radical generated by single-electron transfer (SET) from a boron-based reductant.
- Hu, Jiefeng,Wang, Guoqiang,Li, Shuhua,Shi, Zhuangzhi
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supporting information
p. 15227 - 15231
(2018/10/25)
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- Decarboxylative Borylation of Aliphatic Esters under Visible-Light Photoredox Conditions
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The conventional methods for preparing alkyl boronates often necessitate anhydrous and demanding reaction conditions. Herein, a new, operationally simple decarboxylative borylation reaction of readily available aliphatic acid derivatives under additive-free visible-light photoredox conditions in nonanhydrous solvents has been described. Primary and secondary alkyl boronates or tetrafluoroborates with various functional groups were prepared accordingly. A catalytic cycle involving alkyl radical reaction with base-activated diboron species has been proposed.
- Hu, Dawei,Wang, Linghua,Li, Pengfei
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supporting information
p. 2770 - 2773
(2017/05/24)
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- Synergistic Photoredox/Nickel Coupling of Acyl Chlorides with Secondary Alkyltrifluoroborates: Dialkyl Ketone Synthesis
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Visible light photoredox/nickel dual catalysis has been employed in the cross-coupling of acyl chlorides with potassium alkyltrifluoroborates. This protocol, based on single-electron-mediated alkyl transfer, circumvents the restriction of using reactive alkylmetallic nucleophiles in transition-metal-catalyzed acylation and achieves a mild and efficient method for the synthesis of unsymmetrical alkyl ketones. In this approach, a variety of acyl chlorides have been successfully coupled with structurally diverse potassium alkyltrifluoroborates, generating the corresponding ketones with good yields.
- Amani, Javad,Molander, Gary A.
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p. 1856 - 1863
(2017/02/10)
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- Synergistic Visible-Light Photoredox/Nickel-Catalyzed Synthesis of Aliphatic Ketones via N-C Cleavage of Imides
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An electrophilic, imide-based, visible-light-promoted photoredox/Ni-catalyzed cross-coupling reaction for the synthesis of aliphatic ketones has been developed. This protocol proceeds through N-C(O) bond activation, made possible through the lower activation energy for metal insertion into this bond due to delocalization of the lone pair of electrons on the nitrogen by electron-withdrawing groups. The operationally simple and mild cross-coupling reaction is performed at ambient temperature and exhibits tolerance for a variety of functional groups.
- Amani, Javad,Alam, Rauful,Badir, Shorouk,Molander, Gary A.
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supporting information
p. 2426 - 2429
(2017/05/12)
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- Direct Conversion of Carboxylic Acids to Alkyl Ketones
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An efficient and mild method for acyl-Csp3 bond formation based on the direct conversion of carboxylic acids has been established. This protocol is enabled by the synergistic, Ir-photoredox/nickel catalytic cross-coupling of in situ activated c
- Amani, Javad,Molander, Gary A.
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supporting information
p. 3612 - 3615
(2017/07/15)
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- The facile and direct formylation of organoboron aromatic compounds with benzodithiolylium tetrafluoroborate
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Organoboron compounds can be used to effect a direct formylation in the absence of transition metals. We report that the direct reaction between boronic derivatives and benzodithiolylium tetrafluoroborate, a commercially available carbenium ionic compound, is possible and provides access to many interesting compounds without the use of transition metals. The direct reaction of the carbenium ion with boronic derivatives results in the formation of substituted arylcarbenium ions, a number of which can be further utilized in materials chemistry or for the direct transformation into other compounds. In addition to the rich chameleonic chemical nature of the benzodithiol intermediate, such species can also undergo a metallation reaction and subsequent treatment with a wide range of electrophiles to access a variety of functional groups (aldehyde, ketone, acid, and alkyl groups). Copyright
- Petruzziello, Diego,Gualandi, Andrea,Jaffar, Hamza,Lopez-Carrillo, Veronica,Cozzi, Pier Giorgio
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p. 4909 - 4917
(2013/08/23)
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- Preparation of organotrifluoroborate salts: Precipitation-driven equilibrium under non-etching conditions
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Simple, rapid, and scaleable: In contrast to current procedures using corrosive HF/MF or MHF2 reagents (M=e.g. K), a wide range of trifluoroborates can be rapidly, simply, and safely prepared from MF (M=K, Cs), RCO2H, and a boronic a
- Lennox, Alastair J. J.,Lloyd-Jones, Guy C.
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supporting information
p. 9385 - 9388
(2012/10/29)
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- Oxidative nucleophilic substitution: Transformation of alkylboronic derivatives
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An efficient amidation reaction is described in this paper. Potassium alkyltrifluoroborate salts can be transforming to amides from nitriles in the presence of copper acetate and boron trifluoride. An extension of this reaction allowed the formation of amines, ethers, and C-C bond.
- Cazorla, Clément,Métay, Estelle,Lemaire, Marc
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experimental part
p. 8615 - 8621
(2011/11/30)
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- Stereoselective nucleophilic addition of potassium alkyltrifluoroborates to cyclic N-acyliminium ions: A Simple and mild approach to chiral 5-alkyl-pyrrolidin-2-ones
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The stereoselective nucleophilic addition of potassium alkyltrifluoroborates to cyclic N-acyliminium ions derived from N-benzyl-3,4,5-triacetoxy-pyrrolidin-2-one, which affords 5-substituted- pyrrolidin-2-ones, is described. The products are obtained in moderate to good yields and are produced predominantly as the anti diastereomer.
- Vieira, Adriano S.,Ferreira, Fernando P.,Guarezemini, Alexandre S.,Stefani, Helio A.
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experimental part
p. 909 - 916
(2010/02/16)
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- Efficient cross-coupling of secondary alkyltrifluoroborates with aryl chlorides-reaction discovery using parallel microscale experimentation
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Microscale parallel experimentation was used to discover three catalyst systems capable of coupling secondary organotrifluoroborates with sterically and electronically demanding aryl chlorides and bromides. The ensuing results represent the first comprehensive study of alkylboron coupling to aryl chlorides and, in particular, using secondary alkylboron partners. A ligand-dependent β-hydride elimination/reinsertion mechanism was implicated in the cross-coupling of more hindered substrates, leading to isomeric mixtures of coupled products in some cases. Copyright
- Dreher, Spencer D.,Dormer, Peter G.,Sandrock, Deidre L.,Molander, Gary A.
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supporting information; body text
p. 9257 - 9259
(2009/02/02)
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- Hydroboration with pyridine borane at room temperature
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Treatment of pyridine borane (Py·BH3) with iodine, bromine, or strong acids affords activated Py·BH2X complexes that are capable of hydroborating alkenes at room temperature. Evidence is presented for an unusual hydroboration mechanism involving leaving group displacement. In contrast to THF·BH3, hydroboration with Py·BH2I selectively affords the monoadducts. The crude hydroboration products are converted into synthetically useful potassium alkyltrifluoroborate salts upon treatment with methanolic KHF2. Copyright
- Clay, Julia M.,Vedejs, Edwin
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p. 5766 - 5767
(2007/10/03)
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- Asymmetric alkyldifluoroboranes and their use in secondary amine synthesis
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(matrix presented) Asymmetric diol boronic esters with potassium bifluoride form the corresponding alkyltrifluoroborate and free diol under mild conditions. Defluoridation with tetrachlorosilane produces an alkyldifluoroborane intermediate. This conversio
- Matteson, Donald S.,Kim, Gyung Youn
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p. 2153 - 2155
(2007/10/03)
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