5031-83-4Relevant articles and documents
Chichibabin pyridinium synthesisviaoxidative decarboxylation of photoexcited α-enamine acids
Pan, Zhiqiang,Hu, Fengchi,Jiang, Di,Liu, Yuchang,Xia, Chengfeng
, p. 1222 - 1225 (2021)
A visible light-induced decarboxylative Chichibabin pyridinium synthesis between α-amino acids and aldehydes was developed. When thein situgenerated α-enamine acids were photoexcited, they were oxidized by aerobic oxygen to give radical cation species. After decarboxylation and further oxidation, the generated iminium undergoes Chichibabin cyclization to afford pyridiniums. This photochemical protocol enables the synthesis of various tetra-substituted pyridiniums and related natural products in one-step.
H4SiW12O40-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides: An efficient synthesis of 3,4-disubstituted 1H-pyrazoles
Cheng, Mengyuan,Cheng, Yuanyuan,Gao, Xiaofei,Li, Ke,Lin, Xiaoling,Liu, Yufeng,Xie, Xuanjie,Yang, Guoping
supporting information, (2021/09/06)
A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid (H4SiW12O40)-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides/aldehydes were smoothly reacted with sulfonyl hydrazides to furnish regioselectivity 3,4-disubstituted 1H-pyrazoles. The application of such an earth-abundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of 3,4-disubstituted 1H-pyrazoles. A plausible reaction mechanism has been proposed on the basis of control experiments, GC-MS and DFT calculations.
Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
supporting information, p. 18251 - 18265 (2020/11/02)
Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
SELF-CONDENSATION OF ALDEHYDES
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Paragraph 0021; 0027, (2020/06/05)
An efficient process useful for the self-condensation of aliphatic aldehydes is provided, catalyzed by dialkylammonium carboxylate salts. In particular, the invention provides a facile method for the preparation of 2-ethyl hexenal via the self-condensation of butyraldehyde using various dialkylammonium carboxylates, e.g., diisopropylammonium acetate or dimethylammonium acetate, as catalyst. Additionally, residual nitrogen arising from the catalyst can be reduced to -100 ppm levels in the product via a simple washing procedure. The invention provides a process for preparing alkenals under conditions which limit the formation of undesired impurities and high-boiling oligomeric substances.
Performance and coke species of HZSM-5 in the isomerization of styrene oxide to phenylacetaldehyde
Gou, Ming-Lei,Cai, Junqing,Song, Wensheng,Liu, Zhen,Ren, Yun-Lai,Niu, Qingshan
, p. 44247 - 44253 (2017/09/26)
The performance and coke species of HZSM-5 in the isomerization of styrene oxide to phenylacetaldehyde was investigated under gas phase, free of solvents. The reaction showed higher catalytic stability and phenylacetaldehyde selectivity at around 300 °C, lower feed rate (e.g., WHSV = 1.2-3 h-1) and higher flow rate of carrier gas (e.g., 120 mL min-1). Based on FT-IR spectra, the dimer formed via aldol condensation of phenylacetaldehyde was one of the precursors of coke species. TG results showed that there were two types of coke species. The soft coke, which can be removed via desorption between 200-400 °C, had less influence on the catalytic stability. The hard coke, which had a certain degree of crystallization (i.e., pregraphite-like carbon presenting in XRD patterns) and must be completely removed via burning with oxygen, causes major catalyst deactivation.
Pd/C-Catalyzed Carbonylative Esterification of Aryl Halides with Alcohols by Using Oxiranes as CO Sources
Min, Byul-Hana,Kim, Dong-Su,Park, Hyo-Soon,Jun, Chul-Ho
, p. 6234 - 6238 (2016/05/02)
A carbonylative esterification reaction between aryl bromides and alcohols, promoted by Pd/C and NaF in the presence of oxiranes, has been developed. In this process, oxiranes serve as sources of carbon monoxide by their conversion to aldehydes through a palladium-promoted Meinwald rearrangement pathway. Intramolecular versions of this process serve as methods for the synthesis of lactones and phthalimides. CO gas free! A carbonylative esterification reaction between aryl bromides and alcohols, promoted by Pd/C and NaF in the presence of oxiranes, has been developed. In this process, oxiranes serve as sources of carbon monoxide by their conversion to aldehydes through a palladium-promoted Meinwald rearrangement pathway (see scheme).
Reactivity of aminophosphonic acids. Oxidative dephosphonylation of 1-aminoalkylphosphonic acids by aqueous halogens
Drabowicz, Józef,Jordan, Frank,Kudzin, Marcin H.,Kudzin, Zbigniew H.,Stevens, Christian V.,Urbaniak, Pawe?
, p. 2308 - 2317 (2016/02/09)
The reactions of 1-aminoalkylphosphonic acids with bromine-water, chlorine-water and iodine-water were investigated. The formation of phosphoric(v) acid, as a result of a halogen-promoted cleavage of the Cα-P bond, accompanied by nitrogen release, was observed. The dephosphonylation of 1-aminoalkylphosphonic acids was found to occur quantitatively. In the reactions of 1-aminoalkylphosphonic acids with other halogen-water reagents investigated by 31P NMR, scission of the Cα-P bond was also observed, the reaction rates being comparable for bromine and chlorine, but much slower for iodine.
Simple green dehydration in biphasic medium: Application to the synthesis of phenylacetaldehyde
Le Guenic, Sarah,Ceballos, Claire,Len, Christophe
, p. 72 - 77 (2015/11/09)
A highly efficient, simple and versatile acid catalyst is proposed for the selective acid dehydration of 1-phenylethan-1,2-diol to phenylacetaldehyde in water-CPME biphasic media under microwave irradiation. A high stability and recyclability of the catalyst is also observed under the investigated conditions.
Synthesis and reactions of donor cyclopropanes: efficient routes to cis- and trans-tetrahydrofurans
Dunn, Jonathan,Dobbs, Adrian P.
supporting information, p. 7386 - 7414 (2015/08/24)
Abstract A detailed study on the synthesis and reactions of silylmethylcyclopropanes is reported. In their simplest form, these donor-only cyclopropanes undergo Lewis acid promoted reaction to give either cis- or trans-tetrahydrofurans, with the selectivity being reaction condition-dependant. The adducts themselves are demonstrated to be an important scaffold for structural diversification. The combination of a silyl-donor group in a donor-acceptor cyclopropane with novel acceptor groups is also discussed.
Aromatic Monomers by in Situ Conversion of Reactive Intermediates in the Acid-Catalyzed Depolymerization of Lignin
Deuss, Peter J.,Scott, Martin,Tran, Fanny,Westwood, Nicholas J.,De Vries, Johannes G.,Barta, Katalin
supporting information, p. 7456 - 7467 (2015/06/30)
Conversion of lignin into well-defined aromatic chemicals is a highly attractive goal but is often hampered by recondensation of the formed fragments, especially in acidolysis. Here, we describe new strategies that markedly suppress such undesired pathways to result in diverse aromatic compounds previously not systematically targeted from lignin. Model studies established that a catalytic amount of triflic acid is very effective in cleaving the β-O-4 linkage, most abundant in lignin. An aldehyde product was identified as the main cause of side reactions under cleavage conditions. Capturing this unstable compound by reaction with diols and by in situ catalytic hydrogenation or decarbonylation lead to three distinct groups of aromatic compounds in high yields acetals, ethanol and ethyl aromatics, and methyl aromatics. Notably, the same product groups were obtained when these approaches were successfully extended to lignin. In addition, the formation of higher molecular weight side products was markedly suppressed, indicating that the aldehyde intermediates play a significant role in these processes. The described strategy has the potential to be generally applicable for the production of interesting aromatic compounds from lignin.
