630-19-3Relevant articles and documents
Microwave Spectrum, Molecular Structure and Dipole Moment of Pivalaldehyde
Cox, Peter A.,Couch, Andrew D.,Hillig, Kurt W.,LaBarge, Marabeth S.,Kuczkowski, Robert L.
, p. 2689 - 2698 (1991)
The microwave spectra of eight isotopic species of pivalaldehyde have been studied in the frequency region 9-40 GHz.The zero-point average skeletal structure has been derived to be: r = 1.206(6) Angstroem, r = 1.130(5) Angstroem, r = 1.516(7) Angstroem, r = r = 1.537(2) Angstroem, C(1)C(2)C(3) = 110.5(4) deg, C(1)C(2)C(4),(5) = 107.4(3) deg, proj.C(4),(5)C(2)C(1) = 120.78(4) deg, CCO = 126.0(5) deg and CCH(1) = 113.0(3) deg.The tert-butyl group is found to be tilted 2 deg away from the C=O bond.Accurate Stark effect measurements have been performed on the main species, (CH3)3CCDO and (CD3)3CCHO.The ground-state dipole moment of (CH3)3CCHO was determined as μs = 2.618(5) D and μb = 0.728(2) D giving μtotal = 2.717(5) D at an angle of 13.6 deg to the C=O bond.
Bioinspired Radical-Mediated Transition-Metal-Free Synthesis of N-Heterocycles under Visible Light
K. Bains, Amreen,Ankit, Yadav,Adhikari, Debashis
, p. 324 - 329 (2020/11/30)
A redox-active iminoquinone motif connected with π-delocalized pyrene core has been reported that can perform efficient two-electron oxidation of a class of substrates. The design of the molecule was inspired by the organic redox cofactor topaquinone (TPQ), which executes amine oxidation in the enzyme, copper amine oxidase. Easy oxidation of both primary and secondary alcohols happened in the presence of catalytic KOtBu, which could reduce the ligand backbone to its iminosemiquinonate form under photoinduced conditions. Moreover, this easy oxidation of alcohols under aerobic condition could be elegantly extended to multi-component, one-pot coupling for the synthesis of quinoline and pyrimidine. This organocatalytic approach is very mild (70 °C, 8 h) compared to a multitude of transition-metal catalysts that have been used to prepare these heterocycles. A detailed mechanistic study proves the intermediacy of the iminosemiquinonate-type radical and a critical hydrogen atom transfer step to be involved in the dehydrogenation reaction.
Kinetics and correlation analysis of reactivity in the oxidation of aliphatic primary alcohols by isoquinolinium dichromate in non-aqueous medium
Kalal, Reena,Panday, Dinesh
, (2021/06/28)
Mild oxidation in dimethyl sulfoxide (DMSO) medium by isoquinolinium dichromate (IQDC) of aliphatic primary alcohols produces corresponding carbonyl compounds. A Michaelis-Menten kind kinetics noticed as for alcohols while unit dependency on rate observed as for IQDC. At non-identical temperatures the formation constants and the rates of decomposition of alcohol-IQDC complexes have been evaluated. Thermodynamic parameters and activation parameters for formation of the complex and break down of the complexes have been determined respectively. The oxidation process accelerates with increase in proton concentration. An α-C-H bond fisson in the rate-controlling step suggested by the deuterium isotope effect. For oxidation of ethanol, kH/kD = 5.82 at 293 K, was observed. The oxidation rates have been evaluated in 19 organic solvents and greater role of solvating power of the cation is observed. Depended on the kinetic parameters, solvent effect analysis and the outcome of thermodynamic parameters, a mechanism in which rate-controlling break down of the complex is suggested, to give the resulting product through hydride-ion transfer with a cyclic transition state.
Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
, p. 283 - 289 (2020/10/06)
4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
A Multifunctional Microfluidic Platform for High-Throughput Experimentation of Electroorganic Chemistry
Jensen, Klavs F.,Mo, Yiming,Nambiar, Anirudh M. K.,Rughoobur, Girish,Zhang, Kara
supporting information, p. 20890 - 20894 (2020/09/17)
Electroorganic synthesis is a promising tool to design sustainable transformations and discover new reactivities. However, the added setup complexity caused by electrodes in the system impedes efficient screening of reaction conditions. Herein, we present a microfluidic platform that enables automated high-throughput experimentation (HTE) for electroorganic synthesis at a 15-microliter scale. Two HTE modules are demonstrated: 1) the rapid electrochemical reaction condition screening for a radical–radical cross-coupling reaction on micro-fabricated interdigitated electrodes, and 2) measurements of kinetics for mediated anodic oxidations using the microliter-scale cyclic voltammetry. The presented modular approach could be deployed for a range of other electroorganic chemistry applications beyond the demonstrated functionalities.
A Strategy for Accessing Aldehydes via Palladium-Catalyzed C?O/C?N Bond Cleavage in the Presence of Hydrosilanes
He, Zhanyu,Liu, Tingting,Ru, Junxiang,Wang, Yulin,Wang, Zijia,Zeng, Zhuo
, p. 5794 - 5800 (2020/12/01)
We report the catalytic reduction of both active esters and amides by selective C(acyl)?X (X=O, N) cleavage to access aldehyde functionality via a palladium-catalyzed strategy. Reactions are promoted by hydrosilanes as reducing reagents with good to excellent yields and with excellent chemoselectivity for C(acyl)?N and C(acyl)?O bond cleavage. Carboxylic acid C(acyl)?O bonds are activated by 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) to form triazine ester intermediates, which further react with hydrosilanes to yield aldehydes in one-pot two-step procedures. We demonstrate that C(acyl)?O cleavage/formylation offers higher yields and broader substrate scopes compared with C(acyl)?N cleavage under the same reaction conditions.
Convenient synthesis of 2,3-dihydro-1,2,4-thiadiazoles, 4,5-dihydro-1,3-thiazoles, and 1,3-thiazoles through a [4+1]-type oxidative ring closure of 1,3-thiaza-1,3-butadienes
Shimada, Kazuaki,Isogami, Megumi,Maeda, Kitami,Nishinomiya, Rei,Korenaga, Toshinobu
, p. 881 - 900 (2020/09/09)
1,3-Thiaza-1,3-butadienes bearing an N,N-dimethylamino group at the C-2 position were efficiently converted into 5H-1,2,4-oxathiazoles, 2,3-dihydro-1,2,4-thiadiazoles, 4,5-dihydro-1,3-thiazoles, and 1,3-thiazoles through an oxidative ring closure by treating with mCPBA, chloramine-T, metal carbenoids, or dichlorocarbene, respectively, via the ring closure of in situ generated heterocumulene-type reactive species involving thione S-oxides, thione S-imides, and thiocarbonyl ylides.
Transfer hydrogenation of carbon dioxide: Via bicarbonate promoted by bifunctional C-N chelating Cp?Ir complexes
Sato, Yasuhiro,Kayaki, Yoshihito,Ikariya, Takao
supporting information, p. 10762 - 10765 (2020/10/02)
Metal-ligand cooperative Cp?Ir(iii) complexes derived from primary benzylic amines effectively promote transfer hydrogenation of atmospheric CO2 using 2-propanol at 80 °C. Isotope-labelling experiments strengthen that active Ir species can preferentially reduce bicarbonate congeners formed from CO2. The powerful transfer hydrogenation catalyst exhibits remarkable activity for the conversion of bicarbonates into formate salts with a turnover number up to 3200, even without H2 and CO2.
The formyloxyl radical: Electrophilicity, C-H bond activation and anti-Markovnikov selectivity in the oxidation of aliphatic alkenes
Iron, Mark A.,Khenkin, Alexander M.,Neumann, Ronny,Somekh, Miriam
, p. 11584 - 11591 (2020/11/23)
In the past the formyloxyl radical, HC(O)O, had only been rarely experimentally observed, and those studies were theoretical-spectroscopic in the context of electronic structure. The absence of a convenient method for the preparation of the formyloxyl radical has precluded investigations into its reactivity towards organic substrates. Very recently, we discovered that HC(O)O is formed in the anodic electrochemical oxidation of formic acid/lithium formate. Using a [CoIIIW12O40]5- polyanion catalyst, this led to the formation of phenyl formate from benzene. Here, we present our studies into the reactivity of electrochemically in situ generated HC(O)O with organic substrates. Reactions with benzene and a selection of substituted derivatives showed that HC(O)O is mildly electrophilic according to both experimentally and computationally derived Hammett linear free energy relationships. The reactions of HC(O)O with terminal alkenes significantly favor anti-Markovnikov oxidations yielding the corresponding aldehyde as the major product as well as further oxidation products. Analysis of plausible reaction pathways using 1-hexene as a representative substrate favored the likelihood of hydrogen abstraction from the allylic C-H bond forming a hexallyl radical followed by strongly preferred further attack of a second HC(O)O radical at the C1 position. Further oxidation products are surmised to be mostly a result of two consecutive addition reactions of HC(O)O to the CC double bond. An outer-sphere electron transfer between the formyloxyl radical donor and the [CoIIIW12O40]5- polyanion acceptor forming a donor-acceptor [D+-A-] complex is proposed to induce the observed anti-Markovnikov selectivity. Finally, the overall reactivity of HC(O)O towards hydrogen abstraction was evaluated using additional substrates. Alkanes were only slightly reactive, while the reactions of alkylarenes showed that aromatic substitution on the ring competes with C-H bond activation at the benzylic position. C-H bonds with bond dissociation energies (BDE) ≤ 85 kcal mol-1 are easily attacked by HC(O)O and reactivity appears to be significant for C-H bonds with a BDE of up to 90 kcal mol-1. In summary, this research identifies the reactivity of HC(O)O towards radical electrophilic substitution of arenes, anti-Markovnikov type oxidation of terminal alkenes, and indirectly defines the activity of HC(O)O towards C-H bond activation.
Pd-Catalyzed Dehydrogenative Oxidation of Alcohols to Functionalized Molecules
Mori, Takamichi,Ishii, Chihiro,Kimura, Masanari
supporting information, p. 1709 - 1717 (2019/09/04)
A dehydrogenative oxidation reaction of primary alcohols to aldehydes catalyzed by a simple Pd/Xantphos catalytic system was developed under an argon or nitrogen atmosphere without oxidizing agents or hydrogen acceptors. The reaction product could be easily changed: under aerobic conditions, esters were obtained in aprotic solvents, whereas the corresponding carboxylic acids were produced in aqueous media. These oxidizing processes were applicable to the efficient synthesis of useful nitrogen-containing heterocyclic compounds such as indole, quinazoline, and benzimidazole via intramolecular versions of this reaction from amino alcohols.
