1918-79-2Relevant academic research and scientific papers
Pd(II)-Catalyzed asymmetric oxidative annulation of N-alkoxyheteroaryl amides and 1,3-dienes
Zhang, Tao,Shen, Hong-Cheng,Xu, Jia-Cheng,Fan, Tao,Han, Zhi-Yong,Gong, Liu-Zhu
supporting information, p. 2048 - 2051 (2019/03/29)
The first Pd(II)-catalyzed asymmetric oxidative annulation of N-alkoxyaryl amides and 1,3-dienes is reported, which features particular applicability for quick assembly of different types of chiral heterocycles with high yields and enantioselectivities. A novel chiral pyridine-oxazoline bearing a methoxyl group at the C-5 position and a gem-dimethyl group on the oxazoline moiety was found to be crucial for conversion.
A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids
Knaus, Tanja,Tseliou, Vasilis,Humphreys, Luke D.,Scrutton, Nigel S.,Mutti, Francesco G.
supporting information, p. 3931 - 3943 (2018/09/11)
Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-Aliphatic, benzylic, hetero-Aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-Type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.
EtAlCl2/2,6-Disubstituted Pyridine-Mediated Carboxylation of Alkenes with Carbon Dioxide
Tanaka, Shinya,Watanabe, Kota,Tanaka, Yuuki,Hattori, Tetsutaro
supporting information, p. 2576 - 2579 (2016/06/15)
α-Arylalkenes and trialkyl-substituted alkenes undergo carboxylation with CO2 in the presence of EtAlCl2 and 2,6-dibromopyridine to afford the corresponding α,β- and/or β,γ-unsaturated carboxylic acids. This reaction is suggested to proceed via the electrophilic substitution of EtAlCl2 with the aid of the base, followed by the carbonation of the resulting ate complex. This reaction can be applied to terminal dialkylalkenes by using a mixture of 2,6-di-tert-butylpyridine and 2,6-dibromopyridine.
2-Oxo-Driven Coupling Reactions of 2-Oxo Aldehydes/2-Oxo Iminium Ions and Hydroperoxides at Room Temperature
Khan, Shahnawaz,Ahmed, Qazi Naveed
, p. 5377 - 5385 (2016/11/22)
An efficient 2-oxo-group-promoted direct coupling reaction between 2-oxo aldehydes and hydroperoxides has been developed. The method has been used successfully for the generation of different 2-oxo esters and acids. This reaction harnesses the hydrogen-bonding-induced self-decomposition tendency of hydroperoxides; the intermediates produced by this process then attack the aldehyde or iminium ion to generate cross-coupled products either by direct coupling or by an amine-catalysed pathway. No external oxidants or metal catalysts are required for our method, and the reaction takes place at room temperature.
A Metal-Free Approach to Carboxylic Acids by Oxidation of Alkyl, Aryl, or Heteroaryl Alkyl Ketones or Arylalkynes
Aravinda Kumar,Venkateswarlu, Vunnam,Vishwakarma, Ram A.,Sawant, Sanghapal D.
, p. 3161 - 3168 (2015/10/19)
The metal-free oxidation of dialkyl, alkyl aryl, or alkyl heteroaryl ketones or arylalkynes to the corresponding carboxylic acids is achieved using an oxidative mixture of Oxone and trifluoroacetic acid. This green method is a simple and mild protocol to obtain carboxylic derivatives in excellent yields.
Metal-free oxidative cleavage of the C-C bond in α-hydroxy-β-oxophosphonates
Battula, Satyanarayana,Kumar, Atul,Ahmed, Qazi Naveed
supporting information, p. 9953 - 9956 (2015/10/12)
The potential of TBHP to promote oxidative hydroxylation of α-hydroxy-β-oxophosphonates (HOPs) through C(CO)-C bond cleavage is described. This cleavage, as depicted in the mechanism is expected through an isomer of HOP that reacts with TBHP to generate acids.
DMSO/I2 mediated C-C bond cleavage of α-ketoaldehydes followed by C-O bond formation: A metal-free approach for one-pot esterification
Venkateswarlu, Vunnam,Aravinda Kumar,Gupta, Sorav,Singh, Deepika,Vishwakarma, Ram A.,Sawant, Sanghapal D.
, p. 7973 - 7978 (2015/07/27)
A novel and efficient I2/DMSO mediated metal-free strategy is presented for the direct C-C bond cleavage of aryl-/heteroaryl- or aliphatic α-ketoaldehydes by C2-decarbonylation and C1-carbonyl oxidation to give the corresponding carboxylic acids followed by esterification in one pot, offering excellent yields in both the steps. Here, DMSO acts as the oxygen source/oxidant and this reaction works very well under both conventional heating and microwave irradiation. This is a very simple and convenient protocol.
Flash carboxylation: Fast lithiation-carboxylation sequence at room temperature in continuous flow
Pieber, Bartholomaeus,Glasnov, Toma,Kappe
, p. 13430 - 13433 (2014/04/03)
A method for the direct lithiation of terminal alkynes and heterocycles with subsequent carboxylation in a continuous flow format was developed. This method provides carboxylic acids at ambient conditions within less than five seconds with only little excess of the organometallic base and CO2. This journal is the Partner Organisations 2014.
Preparation and NMR studies of cobalt-containing diphosphine ligand chelated W, Ru, Au and Pd complexes: Suzuki cross-coupling reactions and carbonylation catalyzed by the Pd complex
Hong, Fung-E,Chang, Yu-Chang,Chang, Chin-Pei,Huang, Yi-Luen
, p. 157 - 165 (2007/10/03)
Treatment of a cobalt-containing diphosphine ligand, [{μ-P,P-PPh2CH2PPh2}Co2(CO)4 {μ-PPh2C≡CPPh2}] 1 with metal complexes W(CO)6, Ru3(CO)12, AuCl(tht) (tht = tetrahydrothiophene) and (COD)PdCl2 (COD = 1,5-cycloctadiene) gave 1-chelated metal complexes [(1)W(CO)4] 3, [(μ-1)Ru3(CO)10] 4, [(1)(AuCl)2] 5 and [(1)PdCl2] 6, respectively. All these compounds were characterized by spectroscopic means whereas 3, 4 and 6 were also studied by X-ray diffraction. These compounds display chelating and bridging modes of metal-phosphine complexation. Variable-temperature 1H and 31P NMR experiments were carried out for 3-6 and revealed that the fluxional behavior of each individual bridging dppm fragment was affected greatly by the bite angle of 1 in each metal complex. Suzuki cross-coupling reactions were satisfactorily catalyzed by 6 under mild conditions. The reactions of aryl halides or iodothiophenes with chloroform and alkali in biphasic solution utilizing a catalytic amount of 6 result into the formation of benzoic and thiophenic acids, respectively.
