- Bifunctional water activation for catalytic hydration of organonitriles
-
Treatment of [Rh(COD)(μ-Cl)]2 with excess tBuOK and subsequent addition of 2 equiv of PIN?HBr in THF afforded [Rh(COD)(κC2-PIN)Br] (1) (PIN = 1-isopropyl-3-(5,7-dimethyl-1, 8-naphthyrid-2-yl)imidazol-2-ylidene, COD = 1,5-cyclooctadiene). The X-ray structure of 1 confirms ligand coordination to "Rh(COD)Br" through the carbene carbon featuring an unbound naphthyridine. Compound 1 is shown to be an excellent catalyst for the hydration of a wide variety of organonitriles at ambient temperature, providing the corresponding organoamides. In general, smaller substrates gave higher yields compared with sterically bulky nitriles. A turnover frequency of 20 000 h-1 was achieved for the acrylonitrile. A similar Rh(I) catalyst without the naphthyridine appendage turned out to be inactive. DFT studies are undertaken to gain insight on the hydration mechanism. A 1:1 catalyst-water adduct was identified, which indicates that the naphthyridine group steers the catalytically relevant water molecule to the active metal site via double hydrogen-bonding interactions, providing significant entropic advantage to the hydration process. The calculated transition state (TS) reveals multicomponent cooperativity involving proton movement from the water to the naphthyridine nitrogen and a complementary interaction between the hydroxide and the nitrile carbon. Bifunctional water activation and cooperative proton migration are recognized as the key steps in the catalytic cycle.
- Daw, Prosenjit,Sinha, Arup,Rahaman, S. M. Wahidur,Dinda, Shrabani,Bera, Jitendra K.
-
-
Read Online
- Crosslinkable polyimides obtained from a reactive diamine and the effect of crosslinking on the thermal properties
-
This study presents novel thermally crosslinkable polyimides (PIs)obtained using a diamine (3,5-DABA)containing an amide (CONH2)group. This diamine was highly reactive with pyromellitic dianhydride (PMDA), and the equimolar polyaddition in N-methyl-2-pyrrolidone at room temperature led to a high molecular weight poly(amic acid)(PAA)without causing gelation or precipitation. The results suggest that the amide side group of 3,5-DABA does not participate in PAA polymerization at room temperature. A PI system derived from PMDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB), which has an ultralow coefficient of thermal expansion in the X–Y direction, was modified by copolymerization with 3,5-DABA. The FT-IR spectra suggested that the amide side groups in the 3,5-DABA-modified PIs can react with adjacent imide C=O groups to form crosslinks on heating above 350 °C, even in the absence of sufficient molecular fluidity. This behavior is attributed to the presence of a very high concentration of imide C=O groups distributed in the vicinity of the amide reactive groups. A crosslinking mechanism is proposed in this paper. An effect of crosslinking on the volumetric coefficient of thermal expansion (β)was investigated by comparing the 3,5-DABA-modified PIs with their crosslinker-free counterparts, i.e., a PI derived from PMDA with TFMB and m-phenylenediamine (m-PDA). At a 3,5-DABA content of 20 mol%, the 3,5-DABA-modified copolymer film showed a lower β value than that of the corresponding m-PDA-containing copolymer. The difference in the β values of these copolymers increased with increasing comonomer (3,5-DABA or m-PDA)content. Thus, the use of 3,5-DABA is effective in reducing the β values through crosslinking. Dynamic mechanical analysis showed that crosslinking also contributed to enhancing the storage modulus and broadening the glass transition. 3,5-DABA was also applied to modify the properties of a thermoplastic poly(ester imide)(PEsI). The thermal crosslinking of the 3,5-DABA-modified PEsI caused a Tg enhancement of about 30 °C and an appreciable decrease in the thermoplasticity. Thus, the present approach is also effective in improving the low-Tg character of thermoplastic PIs.
- Hasegawa, Masatoshi,Tokunaga, Ryoko,Hashimoto, Kana,Ishii, Junichi
-
-
Read Online
- Single-electron transfer in aromatic nucleophilic substitution on dinitrobenzonitriles
-
Reaction of OH- with 3,5-dinitrobenzonitrile in water or water-DMSO gives a mixture of unproductive 2- and 4-Meisenheimer complexes that equilibriate and eventually form 3,5-dinitrobenzamide and finally the benzoate ion. The corresponding reaction of 2,4-dinitrobenzonitrile gives the 5-Meisenheimer complex and then a mixture of 2,4-dinitrobenzamide and 2,4-dinitrophenoxide ion. The ratio amide:phenoxide ion increases with increasing [OH-]. These reactions appear to involve formation of charge-transfer complexes of the radical anion of the substrate and ?OH which collapse to give Meisenheimer complexes and final products. The rate constants of the various reaction steps can be estimated by simulation based on relaxation theory, which also fits the product mixture from 2,4-dinitrobenzonitrile. This reaction scheme is consistent with observations of exchange of arene hydrogen and of extensive broadening of 1H NMR signals of the substrates during reaction.
- Bacaloglu, Radu,Blaskó, Andrei,Bunton, Clifford A.,Ortega, Francisco,Zucco, César
-
-
Read Online
- Aerobic oxidation of primary amines to amides catalyzed by an annulated mesoionic carbene (MIC) stabilized Ru complex
-
Catalytic aerobic oxidation of primary amines to the amides, using the precatalyst [Ru(COD)(L1)Br2] (1) bearing an annulated π-conjugated imidazo[1,2-a][1,8]naphthyridine-based mesoionic carbene ligand L1, is disclosed. This catalytic protocol is distinguished by its high activity and selectivity, wide substrate scope and modest reaction conditions. A variety of primary amines, RCH2NH2 (R = aliphatic, aromatic and heteroaromatic), are converted to the corresponding amides using ambient air as an oxidant in the presence of a sub-stoichiometric amount of KOtBu in tBuOH. A set of control experiments, Hammett relationships, kinetic studies and DFT calculations are undertaken to divulge mechanistic details of the amine oxidation using 1. The catalytic reaction involves abstraction of two amine protons and two benzylic hydrogen atoms of the metal-bound primary amine by the oxo and hydroxo ligands, respectively. A β-hydride transfer step for the benzylic C-H bond cleavage is not supported by Hammett studies. The nitrile generated by the catalytic oxidation undergoes hydration to afford the amide as the final product. This journal is
- Yadav, Suman,Reshi, Noor U Din,Pal, Saikat,Bera, Jitendra K.
-
p. 7018 - 7028
(2021/11/17)
-
- A mild and selective Cu(II) salts-catalyzed reduction of nitro, azo, azoxy, N-aryl hydroxylamine, nitroso, acid halide, ester, and azide compounds using hydrogen surrogacy of sodium borohydride
-
The first mild, in situ, single-pot, high-yielding well-screened copper (II) salt-based catalyst system utilizing the hydrogen surrogacy of sodium borohydride for selective hydrogenation of a broad range of nitro substrates into the corresponding amine under habitancy of water or methanol like green solvents have been described. Moreover, this catalytic system can also activate various functional groups for hydride reduction within prompted time, with low catalyst-loading, without any requirement of high pressure or molecular hydrogen supply. Notably, this system explores a great potential to substitute expensive traditional hydrogenation methodologies and thus offers a greener and simple hydrogenative strategy in the field of organic synthesis.
- Kalola, Anirudhdha G.,Prasad, Pratibha,Mokariya, Jaydeep A.,Patel, Manish P.
-
supporting information
p. 3565 - 3589
(2021/10/12)
-
- Ti-superoxide catalyzed oxidative amidation of aldehydes with saccharin as nitrogen source: Synthesis of primary amides
-
A new heterogeneous catalytic system (Ti-superoxide/saccharin/TBHP) has been developed that efficiently catalyzes oxidative amidation of aldehydes to produce various primary amides. The protocol employs saccharin as amine source and was found to tolerate a wide range of substrates with different functional groups. Moderate to excellent yields, catalyst reusability and operational simplicity are the main highlights. A possible mechanism and the role of the catalyst in oxidative amidation have also been discussed.
- Kamble, Rohit B.,Mane, Kishor D.,Rupanawar, Bapurao D.,Korekar, Pranjal,Sudalai,Suryavanshi, Gurunath
-
p. 724 - 728
(2020/01/23)
-
- Direct and facile synthesis of primary amides from carboxylic acids via acyl isocyanate intermediates using mukaiyama reagent
-
A very simple and efficient procedure for the preparation of primary amides is described from carboxylic acids using Mukaiyama reagent/KNCO in aqueous acetonitrile. Availability of the reagents, simplicity, and easy workup of the reaction crude make this method attractive for organic chemists.
- Azadi, Roya,Motamedpoor, Zahra
-
p. 801 - 804
(2018/09/26)
-
- Hemilability-Driven Water Activation: A NiII Catalyst for Base-Free Hydration of Nitriles to Amides
-
The NiII complex 1 containing pyridyl- and hydroxy-functionalized N-heterocyclic carbenes (NHCs) is synthesized and its catalytic utility for the selective nitrile hydration to the corresponding amide under base-free conditions is evaluated. The title compound exploits a hemilabile pyridyl unit to interact with a catalytically relevant water molecule through hydrogen-bonding and promotes a nucleophilic water attack to the nitrile. A wide variety of nitriles is hydrated to the corresponding amides including the pharmaceutical drugs rufinamide, Rifater, and piracetam. Synthetically challenging α-hydroxyamides are accessed from cyanohydrins under neutral conditions. Related catalysts that lack the pyridyl unit (i.e., compounds 2 and 4) are not active whereas those containing both the pyridyl and the hydroxy or only the pyridyl pendant (i.e., compounds 1 and 3) show substantial activity. The linkage isomer 1′ where the hydroxy group is bound to the metal instead of the pyridyl group was isolated under different crystallization conditions insinuating a ligand hemilabile behavior. Additional pKa measurements reveal an accessible pyridyl unit under the catalytic conditions. Kinetic studies support a ligand-promoted nucleophilic water addition to a metal-bound nitrile group. This work reports a Ni-based catalyst that exhibits functional hemilability for hydration chemistry.
- Singh, Kuldeep,Sarbajna, Abir,Dutta, Indranil,Pandey, Pragati,Bera, Jitendra K.
-
p. 7761 - 7771
(2017/06/06)
-
- Modular synthesis of 4-aminocarbonyl substituted 1,8-naphthalimides and application in single molecule fluorescence detection
-
Robust methodology to install amide, carbamate, urea and sulfonamide functionality to the 1,8-naphthalimide scaffold has been developed and exemplified. New benzamidonaphthalimide 6, synthesised using this approach, was found to be sensitive to base whereupon fluorescence emission strongly increases (>10-fold) and red-shifts (>4000 cm-1). The optical properties of deprotonated 6 allow for single molecule fluorescence detection, the first example of such behaviour from this class of fluorophore.
- Hearn,Nalder,Cox,Maynard,Bell,Pfeffer,Ashton
-
supporting information
p. 12298 - 12301
(2017/11/20)
-
- Photoinduced intramolecular charge shift reaction in ammonium N-(3,5-dinitrobenzoyl)-α-phenylglycinate adducts
-
Ammonium N-(3,5-dinitrobenzoyl)-α-phenylglycinate adducts were synthesized and characterized by using different protonated amines as counter-ion: NH4+, (CH3-CH2-) 2NH2+, (CH3-CH2-CH 2)NH3+, (CH3-CH2-CH 2-CH2-)NH3+ and (CH 3-CH2-)3NH+. A photochemical process was observed under ultraviolet (λexc, 254 nm) or solar irradiation, both in solid state and in solution: DMSO, acetone or acetonitrile. 3,5-Dinitrobenzene and carboxylate groups, separated by an N-benzylamide bridge, are present in these adducts, acting as electron acceptor and electron donor, respectively. Spectroscopic analyses (NMR, IR and UV-vis) suggest a photoinduced intramolecular electron transfer. A first-order photochemical kinetics was proposed in DMSO/(n-propylammonium N-(3,5-dinitrobenzoyl)-α- phenylglycinate) solution; such behavior was similar for all adducts studied, probably due to total salt dissociation in solution. In the solid state, however, electron transfer process efficiency is directly proportional to Lewis base (amine) strength of the adduct counter-ion. Decarboxylation is observed after the irradiation process, giving rise to a σ-adduct intermediate, and subsequent formation of benzaldehyde and 3,5-dinitrobenzamide degradation products.
- De Souza Coelho, Elaine C.,Da Silva, Aderivaldo P.,Navarro, Daniela M.A. Ferraz,Navarro, Marcelo
-
body text
p. 108 - 111
(2010/12/18)
-
- Method of resolving cis 3-amino-4-(2-(2-furyl)eth-1-yl)-methoxycarbonylmethyl-azetidin-2-one and malic acid salts thereof
-
Cis αα/ββ-3-amino-[2-(2-furyl)eth-1-yl]-1-methoxycarbonylmethyl-azetidin-2-one is resolved via optically active malic acid.
- -
-
-
- Method of resolving cis 3-amino-4-[2-(2-furyl)eth-1-yl]-1-methoxycarbonylmethyl-azetidin-2-one
-
Cis αα/ββ-3-amino-[2-(2-furyl)eth-1-yl]-1-methoxycarbonylmethyl-azetidin-2-one is resolved via optically active tartaric acid.
- -
-
-
- Hydrolysis of various nitrile compounds to the amides by catalysis of 2-mercaptoethanol in a phosphate buffer
-
α-Aminonitriles, 4-nitrobenzonitrile and 3,5-dinitrobenzonitrile were hydrolyzed exclusively to amides efficiently when they were stirred with 2-mercaptoethanol in a phosphate buffer (pH 7.0, 50 mM).
- Lee,Goo,Lee,Lee
-
p. 7439 - 7440
(2007/10/02)
-
- FURTHER FUNCTIONAL GROUP OXIDATIONS USING SODIUM PERBORATE
-
Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N-oxides, and various types of sulfur heterocycles to S,S-dioxides.Nitriles are unaffected by the reagent in acetic acid, but undergo smooth hydration to amides when aqueous methanol is employed as solvent.
- McKillop, Alexander,Kemp, Duncan
-
p. 3299 - 3306
(2007/10/02)
-
- KINETICS AND MECHANISM OF DECOMPOSITION OF RING-SUBSTITUTED N-NITROBENZAMIDES IN AQUEOUS SULFURIC ACID
-
The decomposition rate of a series of meta- and para-substituted N-nitrobenzamides in aqueous sulfuric acid was measured by a spectrophotometric method.It was shown that the main directions of the reaction are cleavage of the N-N or N-C bond in the form of the substrate protonated at the nitrogen atom and also bimolecular decomposition under influence of nucleophiles.The effect of the structure of the N-nitrobenzamide and the acidity of the medium on the direction of decomposition is discussed.
- Drozdova, O. A.,Astrat'ev, A. A.,Kuznetsov, L. L.,Selivanov, V. F.
-
p. 675 - 680
(2007/10/02)
-
- REACTION OF NITRILES WITH 100percent SULFURIC ACID. INFLUENCE OF THE STRUCTURAL EFFECTS OF NITRILES ON THE DIRECTION OF TRANSFORMATION, THE CHARACTER OF COMPLEX FORMATION, AND THE FORM OF THE KINETIC EQUATION
-
The competing directions and kinetics were studied for the reactions of nitriles with 100percent sulfuric aicd.The donor-acceptor interaction between the nitriles and sulfuric acid and DMSO was also investigated.It was shown that variation in the structural effects of the nitriles gives rise to change in the form of the kinetic equation, the ratio between the competing reaction paths, and the character of the donor-acceptor interaction.Situations where the nitrile does not enter into the kinetic equation of the reaction are the most typical.Methods for directed control of the ratio between the competing paths are given.The probable schemes for the mechanism of the reactions are discussed.
- Bodrikov, I. V.,Michurin, A. N.,Vasyanina, G. I.,Bochkareva, N. N.,Krasnoj, V. L.
-
p. 2123 - 2133
(2007/10/02)
-
