19319-26-7Relevant articles and documents
Dehydration of 2-methylbutanal and methyl isopropyl ketone to isoprene using boron and aluminium phosphate catalysts
Hutchings, Graham J.,Hudson, Ian D.,Bethell, Donald,Timms, Don G.
, p. 291 - 299 (1999)
The synthesis of isoprene from the dehydration of 2-methylbutanal is described using boron phosphate, aluminium phosphate, and mixed boron/aluminium phosphates as catalysts. Both boron phosphate and aluminium phosphate deactivate steadily with reaction time due to loss of catalyst activity but the selectivity to isoprene is not significantly affected by catalyst deactivation. Catalyst deactivation is shown to be due to two factors: (i) loss of surface phosphorus and (ii) coke formation. Reactivation of the catalysts at temperatures up to 500°C in an air atmosphere does not successfully restore the catalyst activity, although this procedure does remove all the coke. It is shown that high-temperature calcination (800°C) removes both the surface carbon and restores the surface phosphorus content, and hence this procedure is a necessary prerequisite for the successful reactivation of boron and aluminium phosphate as a catalyst for 2-methylbutanal dehydration. Two samples of aluminium phosphate were studied, prepared from the reaction of phosphoric acid with aluminium chloride or sulfate. The chloride route gives a mixed cristabolite/tridymite AlPO4 and this is shown to be more active than a catalyst containing only the tridymite form of AlPO4 formed from the sulfate route. However, both are less active than BPO4 which can be readily prepared in the cristabolite structure. Mixed B/AlPO4 catalysts (Al:B mol ratio = 1:0.05 and 1:0.1) have also been investigated and these are shown to have a superior catalytic performance when compared with undoped AlPO4. 31P, 27Al, and 11B MAS NMR spectroscopy shows that B and Al are in the same lattice in these mixed phosphate catalysts. Addition of Nb is shown to stabilize the catalytic performance. The BPO4 and AlPO4 catalysts are also shown to be active catalysts for the synthesis of isoprene from methyl isopropyl ketone, which is the major by-product formed from the reaction of 2-methylbutanal. It is suggested that a process for the synthesis of isoprene based on the dehydration of 2-methylbutanal would involve the recycle and conversion of the by-products. The mechanism of the reaction is discussed and it is proposed that 2-methyl-but-2-en-1-ol is an intermediate central to the formation of the two major products of the dehydration reaction: isoprene and methyl isopropyl ketone.
Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenes
He, Jun,Xue, Yuhang,Han, Bo,Zhang, Chunzhu,Wang, You,Zhu, Shaolin
supporting information, p. 2328 - 2332 (2020/01/08)
Starting from diverse alkene-tethered aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β-chiral amines with an enantioenriched aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.
Regulating Hydrogenation Chemoselectivity of α,β-Unsaturated Aldehydes by Combination of Transfer and Catalytic Hydrogenation
Zhou, Yangyang,Li, Zihao,Liu, Yanbo,Huo, Jia,Chen, Chen,Li, Qiling,Niu, Songyang,Wang, Shuangyin
, p. 1746 - 1750 (2020/02/25)
Two hydrogenation mechanisms, transfer and catalytic hydrogenation, were combined to achieve higher regulation of hydrogenation chemoselectivity of cinnamyl aldehydes. Transfer hydrogenation with ammonia borane exclusively reduced C=O bonds to get cinnamyl alcohol, and Pt-loaded metal–organic layers efficiently hydrogenated C=C bonds to synthesize phenyl propanol with almost 100 % conversion rate. The hydrogenation could be performed under mild conditions without external high-pressure hydrogen and was applicable to various α,β-unsaturated aldehydes.
Synthesis of β-Chiral Amines by Dynamic Kinetic Resolution of α-Branched Aldehydes Applying Imine Reductases
Matzel, Philipp,Wenske, Sebastian,Merdivan, Simon,Günther, Sebastian,H?hne, Matthias
, p. 4281 - 4285 (2019/08/20)
Imine reductases (IREDs) allow the one-step preparation of optically active secondary and tertiary amines by reductive amination of ketones. Until now, mainly α-chiral amines have been prepared by this route. In this study, we explored the possibility of synthesizing β-chiral amines, a class of compounds which is also frequently found as structural motif in pharmaceuticals but much more challenging to prepare due to the following reasons: (i) The aldehyde substrate already contains the chiral center and needs to be racemized to enable full conversion. (ii) Because the intermediate imine bears the stereo center two carbon atoms remote to the imine nitrogen, it is more challenging to achieve high enantioselectivity compared to α-chiral amine synthesis. For investigating the proof of concept, we first confirmed that different IREDs are able to convert a variety of α-branched aldehydes when combined with five different amine substrates. The IRED from Streptomyces ipomoeae was a suitable enzyme facilitating the dynamic kinetic resolution of 2-phenylpropanal and a substituted 2-methyl-3-phenylpropanal: the corresponding N-methylated β-chiral amines were obtained with '95 % conversion and 78 and 95 %ee. Other amines were formed with low to moderate enantiomeric excess. This exemplifies the potential of IREDs for the one-step synthesis of secondary β-chiral amines, but also the challenge to identify highly selective enzymes for a desired amine product.
Asymmetric Aza-Wacker-Type Cyclization of N-Ts Hydrazine-Tethered Tetrasubstituted Olefins: Synthesis of Pyrazolines Bearing One Quaternary or Two Vicinal Stereocenters
Kou, Xuezhen,Shao, Qihang,Ye, Chenghao,Yang, Guoqiang,Zhang, Wanbin
supporting information, p. 7587 - 7597 (2018/06/04)
We have developed an asymmetric aza-Wacker-type cyclization of N-Ts hydrazine-tethered tetrasubstituted olefins, affording optically active pyrazolines bearing chiral tetrasubstituted carbon stereocenters. This reaction is tolerant to a broad range of substrates under mild reaction conditions, giving the desired chiral products with high enantioselectivities. Generation of two vicinal stereocenters on the C=C double bonds was also achieved with high selectivities, a process which has been rarely studied for Wacker-type reactions. A mechanistic study revealed that this aza-Wacker-type cyclization undergoes a syn-aminopalladation process. It was also found that for substrates bearing two linear alkyl substituents on the outer carbon atom of the olefin, both of which are larger than a methyl group, the alkyl substituent that is cis to the intranucleophilic group participates more readily in β-hydride elimination. When one of the two alkyl substituents on the outer carbon atom of the olefin is a methyl group, β-hydride elimination proceeds selectively at the methylene side, thus both diastereomers can be prepared via switching the configuration of the olefin. Furthermore, the product can be converted to a pharmaceutical compound in high yields over three steps.
The remarkable promotion of in situ formed Pt-cobalt oxide interfacial sites on the carbonyl reduction to allylic alcohols
Li, Chenyue,Ke, Changxuan,Han, Ruirui,Fan, Guoli,Yang, Lan,Li, Feng
, p. 78 - 87 (2018/06/06)
Pt catalysts attract increasing attention for selectively hydrogenating α,β-unsaturated aldehydes to produce allylic alcohols, thanks to their relatively satisfactory selectivity towards the reduction of C[dbnd]O bond over C[dbnd]C bond. Here, new carbon supported cobalt oxide-decorated platinum nanocatalysts for highly selective hydrogenation of cinnamaldehyde were fabricated via a facile composite precursor route. As-fabricated cobalt oxide-decorated Pt catalyst at a Co/Pt atomic ratio of 0.6 was found to exhibit an exceptional catalytic performance with an extremely high 99% yield of cinnamyl alcohol under mild reaction conditions (2 MPa H2 and 80 °C). In contrast to that of the undecorated Pt one, the intrinsic activity of the cobalt oxide-decorated Pt-based one, i.e. the turnover frequency for cinnamaldehyde conversion (4.19 s?1), was significantly increased by 9.5 times. The present catalyst system presents a particularly dramatic enhancement in catalytic performance, in comparison with other Pt-based hydrogenation catalysts previously reported. Such exceptional catalytic efficiency was probably corelated with unique geometric and electronic modifications of Pt particles by CoOx species, thereby giving rise to both the increased exposed active metal surface and the favorable electron-rich state of Pt0 species. Correspondingly, the rate of cinnamaldehyde conversion could be improved and the adsorption of the carbonyl group could be strengthened. This synergy between CoOx species and Pt sites is accounted for the observed superiority of CoOx-decorated Pt catalyst to Co-free Pt one in selective hydrogenation of carbonyl compounds.
Mizoroki–Heck Cyclizations of Amide Derivatives for the Introduction of Quaternary Centers
Medina, Jose M.,Moreno, Jesus,Racine, Sophie,Du, Shuaijing,Garg, Neil K.
supporting information, p. 6567 - 6571 (2017/05/29)
We report non-decarbonylative Mizoroki–Heck reactions of amide derivatives. The transformation relies on the use of nickel catalysis and proceeds using sterically hindered tri- and tetrasubstituted olefins to give products containing quaternary centers. The resulting polycyclic or spirocyclic products can be obtained in good yields. Moreover, a diastereoselective variant of this method gives access to an adduct bearing vicinal, highly substituted sp3 stereocenters. These results demonstrate that amide derivatives can be used as building blocks for the assembly of complex scaffolds.
METHOD FOR PRODUCING UNSATURATED ALCOHOL
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Paragraph 0074-0076, (2017/01/02)
PROBLEM TO BE SOLVED: To provide a method for producing an unsaturated alcohol that uses an unsaturated carbonyl compound as a raw material and can produce an unsaturated alcohol in which only the carbonyl bond of the unsaturated carbonyl compound is selectively reduced with excellent reaction rate, high selectivity and high yield. SOLUTION: The process for producing an unsaturated alcohol includes a step of allowing the reductive reaction of a 3C or more unsaturated carbonyl compound having one or more carbon-carbon unsaturated bonds in the molecule with hydrogen to proceed in the presence of a catalyst comprising at least one kind of metal selected from the group consisting of cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, silver, osmium, iridium and platinum and at least one kind of metal selected from the group consisting of vanadium, chromium, manganese, iron, molybdenum, tungsten and rhenium to produce a corresponding unsaturated alcohol. COPYRIGHT: (C)2015,JPOandINPIT
SnO2-isolated Pt3Sn alloy on reduced graphene oxide: An efficient catalyst for selective hydrogenation of CO in unsaturated aldehydes
Shi, Juanjuan,Zhang, Mengyuan,Du, Weichen,Ning, Wensheng,Hou, Zhaoyin
, p. 3108 - 3112 (2015/06/08)
In this communication, a pyramid shaped alloy-metal oxide-graphene hybrid was synthesized by a facile procedure, in which SnO2 nanoparticles (NPs) (4.8-5.8 nm) were first coated onto the surface of reduced graphene oxide (rGO), and then very fine Pt3Sn NPs (0.6-1.2 nm) were fabricated on the SnO2 NPs on rGO sheets under microwave irradiation in a few minutes. Characterizations disclosed that the SnO2 NPs on rGO were more favorable for the dispersion of Pt, and Pt3Sn formed mainly on the surface of SnO2 NPs. This pyramid shaped Pt3Sn/SnO2/rGO hybrid was highly active, selective and stable for the hydrogenation of the CO bond in unsaturated aldehydes to unsaturated alcohols under mild conditions.
Rapid synthesis of unsaturated alcohols under mild conditions by highly selective hydrogenation
Tamura, Masazumi,Tokonami, Kensuke,Nakagawa, Yoshinao,Tomishige, Keiichi
supporting information, p. 7034 - 7036 (2013/09/02)
Ir-ReOx/SiO2 acted as a highly active and selective heterogeneous catalyst for the hydrogenation of unsaturated aldehydes to unsaturated alcohols in water at low H2 pressure (0.8 MPa) and low temperature (303 K). The catalysis is derived from the synergy between Ir metal and ReOx.
