- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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p. 5022 - 5037
(2021/05/04)
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- Copper-Catalyzed Radical N-Demethylation of Amides Using N-Fluorobenzenesulfonimide as an Oxidant
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An unprecedented N-demethylation of N-methyl amides has been developed by use of N-fluorobenzenesulfonimide as an oxidant with the aid of a copper catalyst. The conversion of amides to carbinolamines involves successive single-electron transfer, hydrogen-atom transfer, and hydrolysis, and is accompanied by formation of N-(phenylsulfonyl)benzenesulfonamide. Carbinolamines spontaneously decompose to N-demethylated amides and formaldehyde, because of their inherent instability.
- Yi, Xuewen,Yi, Xuewen,Lei, Siyu,Liu, Wangsheng,Che, Fengrui,Yu, Chunzheng,Liu, Xuesong,Wang, Zonghua,Zhou, Xin,Zhang, Yuexia
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supporting information
p. 4583 - 4587
(2020/05/05)
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- Amide Effects in C?H Activation: Noncovalent Interactions with L-Shaped Ligand for meta Borylation of Aromatic Amides
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A new concept for the meta-selective borylation of aromatic amides is described. It has been demonstrated that while esters gave para borylations, amides lead to meta borylations. For achieving high meta selectivity, an L-shaped bifunctional ligand has been employed and engages in an O???K noncovalent interaction with the oxygen atom of the moderately distorted amide carbonyl group. This interaction provides exceptional control for meta C?H activation/borylation.
- Bisht, Ranjana,Hoque, Md Emdadul,Chattopadhyay, Buddhadeb
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p. 15762 - 15766
(2018/11/10)
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- Direct Synthesis of Amides from Oxidative Coupling of Benzyl Alcohols and N-substituted Formamides Using a Co–Al Based Heterogeneous Catalyst
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Present work reports the direct synthesis of amides from oxidative coupling of benzyl alcohols with various N-substituted formamides using a cobalt-hydrotalcite (Co-HT) derived catalyst. The Co-HT derived catalysts (Co-HT-2, Co-HT-3 and Co-HT-4 having Co2+/Al3+ molar ratio in the catalyst preparation mixture as 1/1, 2/1 and 3/1 respectively) were prepare following a co-precipitation method and characterized well by powder XRD, XPS, FEG-SEM, EDS, DTG–TGA, FT-IR and N2 physisorption measurements. A range of functional amides were obtained in good yields from oxidative coupling of various substituted benzyl alcohols and a range of N-substituted formamides using Co-HT-3 catalyst and oxidant TBHP. Mechanistic investigation suggests that the amidation reaction is associated with the formation and coupling of radical species. Furthermore, the Co-HT derived catalyst was easily recoverable and recyclable with retained high catalytic activity towards the oxidative coupling of benzyl alcohol with DMF. Graphical Abstract: [Figure not available: see fulltext.].
- Subhedar, Dnyaneshwar D.,Gupta, Shyam Sunder R.,Bhanage, Bhalchandra M.
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p. 3102 - 3111
(2018/08/21)
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- Oxidative amidation of benzaldehydes and benzylamines with: N -substituted formamides over a Co/Al hydrotalcite-derived catalyst
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The present work describes a highly efficient synthetic strategy for amides via oxidative coupling of benzaldehydes or benzylamines with N-substituted formamides using a heterogeneous Co/Al hydrotalcite-derived catalyst in the presence of TBHP. A series of Co/Al hydrotalcite-derived catalysts (Cat-2, Cat-3, and Cat-4 with the Co2+/Al3+ molar ratio in the synthesis mixture as 1/1, 2/1 and 3/1) have been prepared by a simple co-precipitation method and characterized using powder XRD, XPS, FEG-SEM, EDS, FT-IR, DTG-TGA and N2 physical adsorption techniques. Among the as-prepared catalysts, Cat-3 exhibited excellent catalytic activity towards the direct amidation of benzaldehydes as well as benzylamines bearing various substituents into the corresponding amides at 100 °C using TBHP as an oxidant. The mechanistic investigation of the amidation reaction revealed that the reaction follows a radical pathway. Furthermore, the catalyst is easily separable and recyclable without considerable loss in catalytic activity.
- Gupta, Shyam Sunder R.,Nakhate, Akhil V.,Rasal, Kalidas B.,Deshmukh, Gunjan P.,Mannepalli, Lakshmi Kantam
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p. 15268 - 15276
(2017/12/15)
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- Contra-Friedel-Crafts tert-butylation of substituted aromatic rings via directed metallation and sulfinylation
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Directed metallation and sulfinylation yields sulfoxides which undergo ipso nucleophilic aromatic substitution with tertiary and secondary alkyllithiums, giving aromatic rings bearing alkyl groups generally incompatible with directed metallation methods and with regioselectivity complementary with classical Friedel-Crafts substitution. The Royal Society of Chemistry 2006.
- Clayden, Jonathan,Stimson, Christopher C.,Keenan, Martine
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p. 1393 - 1394
(2008/02/03)
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- Intramolecular motions in a series of crystalline benzylammonium bromides and dibenzylamines studied by CP/MAS NMR
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A series of 15 compounds including ammonium bromides containing one or two benzyl groups with H, methyl, isopropyl, tert-butyl and tert-amyl substituents and dibenzylamihe with N-isopropyl-, N-tert-butyl- and N-tert-amyl substituents have been synthesised and studied by CP/MAS NMR. The results of dynamic NMR studies on the solids suggest that there is a dramatically wide range of molecular motions occurring in this simple series of compounds: A combination of 2D CPEXSY, dynamic line shape analyses and T1ρ measurements reveals the considerable extent of intramolecular group motions including rotations of methyl, tert-butyl, tert-amyl and phenyl groups. Rates of rotation and activation parameters for these molecular motions are derived where appropriate. In the case of benzyl-tert-butylammonium bromide, where two independent molecules of the compound exist in the asymmetric unit it is shown that the independent processes of tert-butyl rotation in the two molecules have vastly different activation energies that differ by ca. 16 kJ mol-1. The extent of the motions observed suggests that commonly held prejudices about the rigidity of molecules in crystalline solids need revising.
- Riddell, Frank G.,Rogerson, Martin
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p. 493 - 504
(2007/10/03)
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- Base-induced cycloreversion of nitrile oxide cycloadducts: Conversion of imines into secondary and tertiary amides and aromatic aldehydes into acids without a conventional oxidising agent
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A series of substituted Δ2-1,2,4-oxadiazolines (4,5-dihydro-1,2,4-oxadiazoles) 12 have been prepared by 1,3-dipolar cycloaddition of nitrile oxides to imines and are found, upon treatment with KOBut, to undergo cycloreversion to give nitriles and amide anions. These can be protonated to give secondary amides or treated in situ with alkyl halides to give tertiary amides in moderate to good overall yield, although the reaction is restricted to examples with an aromatic substituent at the 5-position. The 1,4,2-dioxazoles 15, formed by cycloaddition of benzonitrile oxide to aromatic aldehydes, similarly undergo cycloreversion allowing direct conversion either into substituted benzoic acids or their methyl esters. Copyright 1996 by the Royal Society of Chemistry.
- Aitken, R. Alan,Raut, Swati V.
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p. 747 - 751
(2007/10/03)
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- The Geometry of Displacements at Nonstereogenic Atoms: The Formal Displacement of Alkoxide from Alkoxyamines by Organolithium Reagents
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Amination of organolithium regents can be achieved by reaction with methyllithium-alkoxyamines.Details of the methodology and analysis of the reaction mechanism are presented.Reactions of methyl-, ethyl-, n-butyl-, sec-butyl-, tert-butyl-, phenyl-, and (o-methoxyphenyl)lithium with methyllithium-methoxyamine give the corresponding amines, isolated as the benzamides, in yields of 71-97percent.Lower yields are obtained with o-lithio-N,N-diisopropylbenzamide, 4-lithiodibenzothiophene, n-butylmagnesium bromide, and phenylmagnesium bromide.Reactions of n-butyl, sec-butyl-, tert-butyl-, and phenyllithium with methyllithium-N-methylmethoxyamine provide the corresponding N-methyl-amines, isolated as the benzamides, in yields of 30-70percent.Retention of the N-methyl group in these reactions is considered to rule out a nitrene intermediate.Involvement of a lithium alkoxyamide is suggested by the formation and substitution of that species by two different routes.Dilithiation of N-methoxy-N-amine (17) gives, after an intramolecular reaction and addition of acetyl chloride, N-acetylindoline, in 78percent yield.Dilithiation of N-methyl-N-amine (19) gives N-methyl-N-acetamide (20), after rection with acetyl chloride.The nitrogen transfer in this conversion is shown by a double labeling experiment to be intermolecular.This results is taken to suggest that the bond angles required for displacement cannot be achieved in a six-membered ring, and the mechanism of the reaction involves a complex in which displacement occurs via an SN2-like transition state.The exocyclic-endocyclic intramolecular-intermolecular test is noted to provide a general approach for determination of the geomatry of reactions at nonstereogenic centers.
- Beak, Peter,Basha, Anwer,Kokko, Bruce,Loo, DeKai
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p. 6016 - 6023
(2007/10/02)
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- THE ELECTROPHILIC AMINATION OF ORGANOLITHIUMS WITH METHYLLITHIUM COMPLEXES OF N-SUBSTITUTED METHOXYAMINES
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Three N-alkyl methoxyamine derivatives are shown to be effective as electrophilic reagents for the conversion of organolithiums to secondary amines.
- Kokko, Bruce J.,Beak, Peter
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p. 561 - 564
(2007/10/02)
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