4088-60-2Relevant academic research and scientific papers
A comparison between conventional and ultrasound-mediated heterogeneous catalysis: Hydrogenation of 3-buten-1-ol aqueous solutions
Disselkamp,Judd,Hart,Peden,Posakony,Bond
, p. 347 - 353 (2004)
A power flow scheme applicable to probe-type ultrasound reactors is presented, that has been deduced from both theoretical estimates and experimental measurements employing a thermal insulated vessel. Under typical conditions for water at 1 atm pressure, 77% of the electrical power is converted into mechanical motion of the probe, that in turn is dissipated to both acoustic power (～12%) and cavitational heating (～88%). Approximately 92% of the mechanical power of the probe was converted into heat, with the remaining power presumably converted into audible acoustic and/or mechanical motion. In a second type of experiment performed here, heterogeneous catalysis experiments have been performed at 298 K in an isothermal (i.e., jacketed) reaction vessel comparing chemistry in conventional (e.g., thermal) versus ultrasound-assisted systems. Both product state distribution and reaction rate measurements have been performed for the hydrogenation (using hydrogen gas) of aqueous 3-buten-1-ol solutions employing Pd-black powder. Products from the heterogeneous catalysis include isomerization to cis- and trans-2-buten-1-ol, as well as hydrogenation to 1-butanol. A reaction scheme involving surface-bound alkyl-radical species, consistent with previous published work, is proposed to explain product formation. Based on the observed differences in cis- to trans-2-buten-1-ol ratios in conventional versus ultrasound experiments, employing untreated and prereduced catalysts, it has been determined that ultrasound creates catalyst site(s) enhancing the cis-to-trans 2-buten-1-ol ratio from 0.25 to 0.55. In addition, comparing the total isomerization to hydrogenation ratio (cis- plus trans-2-buten-1-ol to 1-butanol ratio), for ultrasound-assisted and conventional catalysis, reveal a ～5-fold enhancement in isomerization relative to the more energetically favored hydrogenation due to the application of ultrasound. Finally, the product formation rates for 1-butanol, as well as isomerization plus hydrogenation, revealed that conventional and ultrasound experiments showed both a nonlinear dependence with applied ultrasound power and no differences between untreated and prereduced catalysts. The observed reaction rate enhancements were 1:36:183 for the conventional, 90 W ultrasound, and 190 W ultrasound experiments, respectively.
Deconvoluting the memory effect in Pd-catalyzed allylic alkylation: Effect of leaving group and added chloride
Fristrup, Peter,Jensen, Thomas,Hoppe, Jakob,Norrby, Per-Ola
, p. 5352 - 5360 (2006)
An analysis of product distributions in the Tsuji-Trost reaction indicates that several instances of reported "memory effects" can be attributed to slow interconversion of the initially formed syn- and anti- [Pd(η3-allyl)] complexes. Addition of chloride triggers a true memory effect, in which the allylic terminus originally bearing the leaving group has a higher reactivity. The latter effect, termed regioretention, can be rationalized by ionization from a palladium complex bearing a chloride ion, forming an unsymmetrically substituted [Pd(η3-allyl)] complex. DFT calculations verify that the position trans to the phosphine ligand is more reactive both in the initial ionization and in the subsequent nucleophilic attack.
Non-Cryogenic, Ammonia-Free Reduction of Aryl Compounds
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, (2022/03/31)
A method of reducing an aromatic ring or a cyclic, allylic ether in a compound includes preparing a reaction mixture including a compound including an aromatic moiety or a cyclic, allylic ether moiety, an alkali metal, and either ethylenediamine, diethylenetriamine, triethylenetetramine, or a combination thereof, in an ether solvent; and reacting the reaction mixture at from ?20° C. to 30° C. for a time sufficient to reduce a double bond in the aromatic moiety to a single bond or to reduce the cyclic, allylic ether moiety.
Total Synthesis of Mycinolide IV and Path-Scouting for Aldgamycin N
Herlé, Bart,Sp?th, Georg,Schreyer, Lucas,Fürstner, Alois
supporting information, p. 7893 - 7899 (2021/03/03)
Proof-of-concept is provided that a large estate of 16-membered macrolide antibiotics can be reached by a “unified” approach. The key building block was formed on scale by an asymmetric vinylogous Mukaiyama aldol reaction; its alkene terminus was then converted either into the corresponding methyl ketone by Wacker oxidation or into a chain-extended aldehyde by catalyst-controlled branch-selective asymmetric hydroformylation. These transformations ultimately opened access to two structurally distinct series of macrolide targets. Notable late-stage maneuvers comprise a rare example of a ruthenium-catalyzed redox isomerization of an 1,3-enyne-5-ol into a 1,3-diene-5-one derivative, as well as the elaboration of a tertiary propargylic alcohol into an acyloin by trans-hydrostannation/Chan-Lam-type coupling. Moreover, this case study illustrates the underutilized possibility of forging complex macrolactone rings by transesterification under essentially neutral conditions.
Molecular Recognition and Cocrystallization of Methylated and Halogenated Fragments of Danicalipin A by Enantiopure Alleno-Acetylenic Cage Receptors
Carreira, Erick M.,Diederich, Fran?ois,Fischer, Stefan,Gropp, Cornelius,Husch, Tamara,Trapp, Nils
supporting information, (2020/03/13)
Enantiopure (P)4- and (M)4-configured alleno-acetylenic cage (AAC) receptors offer a highly defined interior for the complexation and structure elucidation of small molecule fragments of the stereochemically complex chlorosulfolipid danicalipin A. Solution (NMR), solid state (X-ray), and theoretical investigations of the formed host-guest complexes provide insight into the conformational preferences of 14 achiral and chiral derivatives of the danicalipin A chlorohydrin core in a confined, mostly hydrophobic environment, extending previously reported studies in polar solvents. The conserved binding mode of the guests permits deciphering the effect of functional group replacements on Gibbs binding energies ΔG. A strong contribution of conformational energies toward the binding affinities is revealed, which explains why the denser packing of larger apolar domains of the guests does not necessarily lead to higher association. Enantioselective binding of chiral guests, with energetic differences ΔΔG293 K up to 0.7 kcal mol-1 between diastereoisomeric complexes, is explained by hydrogen- and halogen-bonding, as well as dispersion interactions. Calorimetric studies (ITC) show that the stronger binding of one enantiomer is accompanied by an increased gain in enthalpy ΔH but at the cost of a larger entropic penalty TΔS stemming from tighter binding.
SYNTHESIS OF (2S,3R,4R)-4,5-DIHYDROXYISOLEUCINE AND DERIVATIVES
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Page/Page column 23, (2019/10/19)
The invention relates to a method for the preparation of a 4,5-dihydroxyisoleucine derivative comprising the steps of asymmetric Claisen rearrangement of a Z-aminocrotyl-glycin ester and subsequent kinetic resolution of the product diastereomer mix by acylase, and subsequent Sharpless dihydroxylation of the resulting 2-amino-3-methylpent-4-enoicacid derivative.
Vapor-phase catalytic dehydration of butanediols to unsaturated alcohols over yttria-stabilized zirconia catalysts
Ohtsuka, Shota,Nemoto, Takuma,Yotsumoto, Rikako,Yamada, Yasuhiro,Sato, Fumiya,Takahashi, Ryoji,Sato, Satoshi
, p. 48 - 57 (2019/02/19)
Vapor-phase catalytic dehydration of butanediols (BDOs) such as 1,3-, 1,4-, and 2,3-butanediol was investigated over yttria-stabilized tetragonal zirconia (YSZ) catalysts as well as monoclinic zirconia (MZ). BDOs were converted to unsaturated alcohols with some by-products over YSZ and MZ. YSZ is superior to MZ for these reactions in a view point of selective formation of unsaturated alcohols. Calcination temperature of YSZ significantly affected the products selectivity as well as the conversion of BDOs: high selectivity to unsaturated alcohols was obtained over the YSZ calcined at high temperatures over 800 °C. In the conversion of 1,4-butanediol at 325 °C, the highest 3-buten-1-ol selectivity of 75.3% was obtained over the YSZ calcined at 1050 °C, whereas 2,3-butanediol was less reactive than the other BDOs. In the dehydration of 1,3-butanediol at 325 °C, in particular, it was found that a YSZ catalyst with a Y2O3 content of 3.2 wt.% exhibited an excellent stable catalytic activity: the highest selectivity to unsaturated alcohols such as 2-buten-1-ol and 3-buten-2-ol over 98% was obtained at a conversion of 66%. Structures of active sites for the dehydration of 1,3-butanediol were discussed using a crystal model of tetragonal ZrO2 and a probable model structure of active site was proposed. The well-crystalized YSZ inevitably has oxygen defect sites on the most stable surface of tetragonal ZrO2 (101). The defect site, which exposes three cations such as Zr4+ and Y3+, is surrounded by six O2? anions. The selective dehydration of 1,3-butanediol to produce 3-buten-2-ol over the YSZ could be explained by tridentate interactions followed by sequential dehydration: the position-2 hydrogen is firstly abstracted by a basic O2? anion and then the position-1 hydroxyl group is subsequently or simultaneously abstracted by an acidic Y3+ cation. Another OH group at position 3 plays an important role of anchoring 1,3-butanediol to the catalyst surface. Thus, the selective dehydration of 1,3-butanediol could proceed via the speculative base-acid-concerted mechanism.
Encapsulation of Crabtree's Catalyst in Sulfonated MIL-101(Cr): Enhancement of Stability and Selectivity between Competing Reaction Pathways by the MOF Chemical Microenvironment
Grigoropoulos, Alexios,McKay, Alasdair I.,Katsoulidis, Alexandros P.,Davies, Robert P.,Haynes, Anthony,Brammer, Lee,Xiao, Jianliang,Weller, Andrew S.,Rosseinsky, Matthew J.
supporting information, p. 4532 - 4537 (2018/03/26)
Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL-101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non-functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well-defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.
Total Synthesis of the Marine Macrolide Amphidinolide F
Ferrié, Laurent,Fenneteau, Johan,Figadère, Bruno
supporting information, p. 3192 - 3196 (2018/06/11)
A new and efficient convergent approach toward the synthesis of amphidinolide F is described through the assembly of three fragments. The two trans-tetrahydrofurans were built by a diastereoselective C-glycosylation with titanium enolate of bulky N-acetyloxazolidinethiones. The side chain was inserted by a Liebeskind-Srogl cross-coupling reaction. A sulfone condensation/desulfonylation sequence, a Stille cross-coupling, and a macrolactonization were applied to connect the fragments.
Total Synthesis of Putative Chagosensine
Heinrich, Marc,Murphy, John J.,Ilg, Marina K.,Letort, Aurélien,Flasz, Jakub,Philipps, Petra,Fürstner, Alois
supporting information, p. 13575 - 13581 (2018/09/25)
The marine macrolide chagosensine is the only natural product known to date that embodies a Z,Z-configured chloro-1,3-diene unit. This distinguishing substructure was prepared by a sequence of palladium-catalyzed 1,2-distannation of an alkyne precursor, regioselective Stille cross-coupling at the terminus of the resulting bisstannyl alkene with an elaborated alkenyl iodide, followed by chloro-destannation of the remaining internal site. The preparation of the required substrates centered on cobalt-catalyzed oxidative cyclization reactions of hydroxylated olefin precursors, which allowed the 2,5-trans-disubstituted tetrahydrofuran rings, embedded into each building block, to be formed with excellent selectivity. The highly strained macrolactone could ultimately be closed under forcing Yamaguchi conditions. Comparison of the spectral data of the synthetic sample with those of authentic chagosensine methyl ester confirmed that the structure of this intriguing compound has been mis-assigned by the isolation team.
