- Model Studies on the Enzyme-Regulated Stereodivergent Cascade Passerini Reaction
-
The synthesis of chiral α-acyloxy carboxamides containing two stereogenic centers continues to be a challenging field of organic chemistry. Herein, we have proposed and proved the feasibility of an enzyme regulated-cascade reaction, which using the same substrates enables the formation of individual stereoisomers of α-acyloxy carboxamides with up to 99 % ee. The access to the individual stereoisomeric products has been achieved by a combination of the enzymatic kinetic resolution of racemic vinyl esters, subsequent Passerini reaction, and enzymatic kinetic resolution of formed α-acyloxy carboxamides. The presented studies are promising in exploratory proof-of-concept of enzyme-controlled stereodivergent cascade to form an important class of chiral compounds for medicinal chemistry.
- Brodzka, Anna,Koszelewski, Dominik,Ostaszewski, Ryszard,Samsonowicz-Górski, Jan,Wilk, Monika
-
supporting information
p. 4161 - 4165
(2021/08/24)
-
- Controllable Intramolecular Unactivated C(sp3)-H Amination and Oxygenation of Carbamates
-
Dual catalyst-controlled intramolecular unactivated C(sp3)-H amination and oxygenation of carbamates merging visible-light photocatalysis and earth-abundant transition metal catalysis have been reported. Useful amino alcohol and diol derivatives could be selectively obtained from readily available tertiary alcohol derivatives. The possible mechanisms have been proposed via a 1,5-HAT process followed by Lewis acid-controlled cyclization. The nickel and zinc catalysts inhibit the formation of oxygenation and amination products, respectively. An interesting phenomenon of chirality transfer is also observed.
- Guo, Qihang,Ren, Xiang,Lu, Zhan
-
supporting information
p. 880 - 884
(2019/05/16)
-
- Selective hydrogenation of α,β-unsaturated carbonyl compounds on silica-supported copper nanoparticles
-
Silica-supported copper nanoparticles prepared via surface organometallic chemistry are highly efficient for the selective hydrogenation of various α,β-unsaturated carbonyl compounds yielding the corresponding saturated esters, ketones, and aldehydes in the absence of additives. High conversions and selectivities (>99%) are obtained for most substrates upon hydrogenation at 100-150 °C and under 25 bar of H2.
- Mendes-Burak, Jorge,Ghaffari, Behnaz,Copéret, Christophe
-
p. 179 - 181
(2019/01/04)
-
- Electrochemical Hydrogenation with Gaseous Ammonia
-
As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.
- Li, Jin,He, Lingfeng,Liu, Xu,Cheng, Xu,Li, Guigen
-
supporting information
p. 1759 - 1763
(2019/01/16)
-
- Preparation method for indanone compound
-
The invention especially relates to a preparation method for an indanone compound, belonging to the field of organic synthesis. The preparation method for the indanone compounds comprises the following steps: 1) subjecting a compound as shown in a formula I and a compound as shown in a formula II to a condensation reaction so as to prepare a compound as shown in a formula III; 2) subjecting the compound as shown in the formula III to hydrolysis in the presence of alkali so as to prepare a compound as shown in a formula IV; and 3) carrying out acylation and ring closure on the compound as shownin the formula IV so as to prepare the as shown in a formula V. Compared with the prior art, the preparation method for the indanone compound in the invention has the advantages of low raw material cost, simple operation, low production of waste water, waste gas and industrial residues, high yield and the like, and is more suitable for industrial production; and compared with various traditionalpreparation methods for the indanone compound, the preparation method of the invention has obvious advantages and shows good industrialization prospects.
- -
-
Paragraph 0087-0089
(2018/08/28)
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- Pyrrolidine-Based P,O Ligands from Carbohydrates: Easily Accessible and Modular Ligands for the Ir-Catalyzed Asymmetric Hydrogenation of Minimally Functionalized Olefins
-
The potential of P,O-iminosugar based ligands in the Ir-catalyzed asymmetric hydrogenation of minimally functionalized olefins is presented. These new ligands were prepared from easily available carbohydrates (D-mannose, D-ribose and D-arabinose). The stereochemical and polyfunctional diversity of carbohydrates allowed the modulation of the ligands, both from their electronic properties and the rigidity of their backbone. High enantioselectivities (ee’s up to 99 %) can be reached in the hydrogenation of selected tri- and disubstituted substrates.
- Elías-Rodríguez, Pilar,Borràs, Carlota,Carmona, Ana T.,Faiges, Jorge,Robina, Inmaculada,Pàmies, Oscar,Diéguez, Montserrat
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p. 5414 - 5424
(2018/12/11)
-
- Synthesis and activity of putative small-molecule inhibitors of the F-box protein SKP2
-
The tetrahydropyran 4-(((3-(2,2-dimethyltetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline was reported to disrupt the SCFSKP2 E3 ligase complex. Efficient syntheses of this tetrahydropyran derivative and analogues, including the des-dimethyl derivative 4-(((3-(tetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline, are described. The enantiomers of the des-dimethyl compound were obtained using Evans' chiral auxiliaries. Structure-activity relationships for these tetrahydropyrans and analogues have been determined by measurement of growth-inhibitory activities in HeLa cells, which indicated a non-specific mechanism of action that correlates with inhibitor lipophilicity. However, preliminary data with (R)-and (S)-4-(((3-(tetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline showed enantioselective inhibition of the degradation of p27 in a cell-based assay that acts as a reporter of SKP2 activity.
- Shouksmith, Andrew E.,Evans, Laura E.,Tweddle, Deborah A.,Miller, Duncan C.,Willmore, Elaine,Newell, David R.,Golding, Bernard T.,Griffin, Roger J.
-
p. 660 - 679
(2015/04/27)
-
- An improved solvent-free system for the microwave-assisted decarboxylation of malonate derivatives based on the use of imidazole
-
A comparative study of the thermal and microwave-assisted decarboxylation of a series of mono- and disubstituted monohydrolyzed malonate derivatives has been carried out. It has been found out that in both circumstances the use of imidazole has a profound effect on the success of the reaction. In general terms the assistance of microwave irradiation accelerates the decarboxylation process significantly and, at the same time, permits the use of minored temperatures with respect to the thermal via. It has been also found that both the thermal and the microwave-assisted transformation can be developed under solvent-free conditions.
- Tellitu, Imanol,Beitia, Itziar,Díaz, Marta,Alonso, Argi?e,Moreno, Isabel,Domínguez, Esther
-
p. 8251 - 8255
(2015/10/05)
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- Iridium catalysts with Chiral bicyclic pyridine-phosphane ligands for the asymmetric hydrogenation of olefins
-
New bicyclic pyridine-phosphane ligands were prepared, and their iridium complexes were evaluated in asymmetric hydrogenation of trisubstituted olefins with non-coordinating and weakly coordinating substituents. The iridium catalysts showed high reactivity and enantioselectivity for both types of olefins. New pyridine-derived N,P-chelated iridium catalysts were prepared and evaluated in the asymmetric hydrogenation of trisubstituted olefins. High conversions and enantioselectivities were obtained. Copyright
- Quan, Xu,Parihar, Vijay Singh,Bera, Milan,Andersson, Pher G.
-
p. 140 - 146
(2014/01/06)
-
- Influence of the position of the substituent on the efficiency of lipase-mediated resolutions of 3-aryl alkanoic acids
-
Hydrolase-catalysed kinetic resolutions to provide enantioenriched α-substituted 3-aryl alkanoic acids are described. (S)-2-Methyl-3- phenylpropanoic acid (S)-1a was prepared in 96% ee by Pseudomonas fluorescens catalysed ester hydrolysis, while, Candida antarctica lipase B (immob) resolved the α-ethyl substituted 3-arylalkanoic acid (R)-1b in 82% ee. The influence of the position of the substituent relative to the ester site on the efficiency and enantioselectivity of the biotransformation is also explored; the same lipases were found to resolve both the α- and β-substituted alkanoic acids. Furthermore, the steric effect of substituents at the C2 stereogenic centre relative to that for their C3 substituted counterparts on the efficiency and stereoselectivity is discussed.
- Deasy, Rebecca E.,Moody, Thomas S.,Maguire, Anita R.
-
p. 1480 - 1487
(2013/12/04)
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- Synthesis of iridium and rhodium complexes with new chiral phosphine-NHC ligands based on 1,1′-binaphthyl framework and their application in asymmetric hydrogenation
-
The first series of chiral phosphine-imidazole carbene ligands based on a 1,1′-binaphthyl framework were synthesized from (R)-2-amine-2′- (diphenylphosphino)-1,1′-binaphthyl (1) in a four-step pathway. After deprotonation of these phosphine-imidazolium sa
- Gu, Peng,Zhang, Jun,Xu, Qin,Shi, Min
-
p. 13599 - 13606
(2013/09/23)
-
- Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
-
α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
- Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
-
supporting information
p. 10609 - 10616
(2012/11/07)
-
- Recent advances in iridium-catalyzed asymmetric hydrogenation: New catalysts, substrates and applications in total synthesis
-
Iridium-catalyzed asymmetric hydrogenation has emerged as a highly efficient method for the synthesis of enantiomerically pure compounds. This account summarizes our recent efforts in this field. We have developed a new type of P,O-ligand that was success
- Ganic, Adnan,Rageot, Denise,Troendlin, Lars,Pfaltz, Andreas
-
scheme or table
p. 187 - 191
(2012/09/21)
-
- Asymmetric hydrogenation of α,β-unsaturated carboxylic esters with chiral iridium N,P ligand complexes
-
Enantioselective conjugate reduction of a wide range of α,β-unsaturated carboxylic esters was achieved using chiral Ir N,P complexes as hydrogenation catalysts. Depending on the substitution pattern of the substrate, different ligands perform best. α,β-Unsaturated carboxylic esters substituted at the α position are less problematic substrates than originally anticipated and in some cases α-substituted substrates actually reacted with higher enantioselectivity than their β-substituted analogues. The resulting saturated esters with a stereogenic center in the α or β position were obtained in high enantiomeric purity. Copyright
- Woodmansee, David H.,Mueller, Marc-Andre,Troendlin, Lars,Hoermann, Esther,Pfaltz, Andreas
-
supporting information
p. 13780 - 13786
(2013/01/15)
-
- Chiral imidate-ferrocenylphosphanes: Synthesis and application as P,N-ligands in iridium(i)-catalyzed hydrogenation of unfunctionalized and poorly functionalized olefins
-
A small library of chiral imidate-ferrocenylphosphane ligands was efficiently synthesized (8 examples) and evaluated in the iridium(i)-catalyzed hydrogenation of unfunctionalized and poorly functionalized olefins. These catalysts perform very well in a range of examples (yields and ee's up to 100%).
- Bert, Katrien,No?l, Timothy,Kimpe, Wim,Goeman, Jan L.,Van Der Eycken, Johan
-
p. 8539 - 8550
(2013/01/15)
-
- A novel alkaline esterase from sporosarcina sp. nov. strain eSP04 catalyzing the hydrolysis of a wide variety of aryl-carboxylic acid esters
-
A novel esterase showing activity specific for esters of aryl-carboxylic acids was discovered in Sporosarcina sp. nov., which was identified by the 16S rDNA sequencing method in addition to morphological and physiological analyses. The aryl-carboxylesterase (named EstAC) was purified 780-fold from crude cell extracts by a 5-step procedure. EstAC was characterized as a monomeric protein with a molecular weight of 43,000, an optimum pH of around 9.0, and an optimum temperature of 40 °C. The pH optimum and the effects of inhibitors together with an internal amino acid sequence suggested that EstAC is a member of family VIII esterases. EstAC was found to be highly active on a wide variety of substrates such as alkyl benzoates, alkyl phenylacetates, ethyl α- or β-substituted phenylpropionates, dialkyl terephthalates, dimethyl isophthalate, and ethylene glycol dibenzoate. However, monomethyl terephthalate was not hydrolyzed. It was suggested that EstAC had 4-hydroxybenzoyl and cinnamoyl esterase activities as well.
- Takehara, Munenori,Kinoshita, Kaori,Miyamoto, Masahiro,Hirohara, Hideo
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p. 1721 - 1727,7
(2012/12/11)
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- Asymmetric hydrogenation of alkenes with planar chiral 2-phosphino-1- aminoferrocene-iridium(I) complexes
-
The first highly enantioenriched and enantiopure planar chiral 2-phosphino-1-aminoferrocene ligands and their Ir(COD)BArF complexes are reported. The ligands display bidentate coordination behavior towards iridium, as indicated by trends in 31P and 1H NMR spectra of the phosphine moieties and the α to nitrogen substituents of the amines. All of the new complexes showed good reactivity as catalysts in promoting asymmetric hydrogenation of several prochiral alkenes, with enantioselectivities up to 92%. Iridium complexes of dimethylaminoferrocene derivatives containing P-Ar groups [PPh2 and P(o-tol)2] gave the highest levels of asymmetric induction.
- Metallinos, Costa,Van Belle, Lori
-
scheme or table
p. 141 - 149
(2011/02/17)
-
- Proline-based P,O ligand/iridium complexes as highly selective catalysts: Asymmetric hydrogenation of trisubstituted alkenes
-
P,O joins the mix: P,O ligands (L1) form efficient iridium catalysts for the asymmetric hydrogenation of olefins. The proline-derived ligands lead to high enantioselectivities with several classes of alkenes, most notably with α,β-unsaturated carboxylic e
- Rageot, Denise,Woodmansee, David H.,Pugin, Benoet,Pfaltz, Andreas
-
supporting information; experimental part
p. 9598 - 9601
(2011/12/05)
-
- Rh-catalyzed asymmetric hydroformylation of functionalized 1,1-disubstituted olefins
-
The first method for the highly enantioselective rhodium-catalyzed hydroformylation of 1,1-disubstituted olefins has been developed. By employing either of the P-chirogenic phosphine ligands BenzP* and QuinoxP*, linear aldehydes with β-chirality can be prepared in a highly enantioselective fashion with good chemo- and regioselectivities.
- Wang, Xiao,Buchwald, Stephen L.
-
supporting information; scheme or table
p. 19080 - 19083
(2012/01/05)
-
- Iridium-catalyzed asymmetric hydrogenation of olefins using TIQ phosphine-oxazoline ligands
-
A novel family of tetrahydroisoquinoline (TIQ) phosphine-oxazoline ligands and four corresponding iridium complexes have been developed and applied to the asymmetric hydrogenation of unfunctionalized olefins. The results showed that the best conversion rates were observed in up to 99% with an enantiomeric excess of 91%.
- Chakka, Sai Kumar,Peters, Byron K.,Andersson, Pher G.,Maguire, Glenn E.M.,Kruger, Hendrik G.,Govender, Thavendran
-
experimental part
p. 2295 - 2301
(2010/11/04)
-
- Bicyclic phosphine-thiazole ligands for the asymmetric hydrogenation of olefins
-
New bicyclic thiazole-based chiral N,P-chelating ligands were developed. High activities and enantioselectivities were achieved in the iridium-catalyzed asymmetric hydrogenation of olefins with the new ligands.
- Li, Jia-Qi,Paptchikhine, Alexander,Govender, Thavendran,Andersson, Pher G.
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experimental part
p. 1328 - 1333
(2010/10/21)
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- Iridium catalysts with chiral imidazole-phosphine ligands for asymmetric hydrogenation of vinyl fluorides and other olefins
-
New chiral bidentate imidazole-phosphine ligands have been prepared and evaluated for the iridium-catalysed asymmetric hydrogenation of olefins. The imidazole-phosphine-ligated iridium catalysts hydrogenated trisubstituted olefins with the same sense of enantiodiscrimination as known iridium catalysts possessing oxazole and thiazole as N-donors. The imidazole-based catalysts were shown to hydrogenate vinyl fluorides, in some cases with the highest ee values published to date.
- Kaukoranta, Paeivi,Engman, Mattias,Hedberg, Christian,Bergquist, Jonas,Andersson, Pher G.
-
supporting information; experimental part
p. 1168 - 1176
(2009/05/27)
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- Chiral bis(N-arylamino)phosphine-oxazolines: Synthesis and application in asymmetric catalysis
-
N-Arylation or N-alkylation of chiral 1,2-diamines followed by ring closure with phosphorus trichloride (PCl3) and subsequent coupling with an oxazoline alcohol resulted in a new class of N,P ligands. The corresponding iridium tetrakis[3,5-bis(trifluormethyl)phenyl]borate (BArF) complexes were found to be efficient catalysts for the enantioselective hydrogenation of unfunctionalized olefins and α,β-unsaturated carboxylic esters.
- Schoenleber, Marc,Hilgraf, Robert,Pfaltz, Andreas
-
supporting information; experimental part
p. 2033 - 2038
(2009/08/07)
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- Borrowing hydrogen in an indirect asymmetric Wittig reaction
-
An asymmetric C-C bond formation has been achieved by iridium-catalysed coupling of benzyl alcohol with a phosphonium ylide using a borrowing hydrogen strategy.
- Shermer, Duncan J.,Slatford, Paul A.,Edney, Dean D.,Williams, Jonathan M.J.
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p. 2845 - 2848
(2008/09/17)
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- Enantioselective hydrogenation of olefins with axial chiral iridium QUINAP complex
-
(S)-QUINAP reacted with [Ir(cod)Cl]2 to form a new chelating iridium complex in 77.4% yield. The iridium complex was proved to be a highly efficient catalyst for the enantioselective hydrogenation of olefins. 33.4-95.1% ee were obtained for the hydrogenation of unfunctionalized olefins and 90.8-96.1% ee were obtained for functionalized olefins.
- Li, Xinsheng,Kong, Lichun,Gao, Yongguang,Wang, Xiaoxia
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p. 3915 - 3917
(2008/02/03)
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- Development of pinene-derived N,P ligands and their utility in catalytic asymmetric hydrogenation
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New diastereomeric N,P-ligands, derived from the natural product (+)-α-pinene, have been synthesized and evaluated in iridium-catalyzed asymmetric hydrogenation. The ligands are tetrahydroquinoline derivatives synthesized directly from commercially available α-pinene utilizing resolution or recrystallization to separate diastereomers. In reduction of a range of different trisubstituted alkenes the catalysts express very different activities ranging from no activity to high activity. One of the catalysts gives good ee values for some substrates. The Royal Society of Chemistry.
- Verendel, J. Johan,Andersson, Pher G.
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p. 5603 - 5610
(2008/09/17)
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- Asymmetric hydrogenation of trisubstituted olefins with iridium-phosphine thiazole complexes: A further investigation of the ligand structure
-
New chiral bidentate phoshine thiazoles have been prepared and successfully applied as ligands in the homogeneous iridium-catalyzed asymmetric hydrogenation of aryl alkenes and aryl alkene esters. The ligands are designed to be highly modular and have one common chiral intermediate, from which diversity can be introduced at a late stage in the synthetic pathway. It was found that a six-member-ring backbone of the rigid ligand structure was preferred over seven- or five-member rings. In this study it is shown that the substituent pattern of the ligands has a major influence on the stereochemical outcome of the products. By applying the selectivity model proposed in this study, it is possible to match different substrates against different catalysts. In this way, good to excellent enantioselectivity can be obtained for typically difficult substrates. Geometrically different derivatives of α- and β-methyl cinnamic acid ethyl esters were hydrogenated, to demonstrate the validity of the selectivity model and to verify the importance of steric and electronic matching of the catalyst and the substrate.
- Hedberg, Christian,Kaellstroem, Klas,Brandt, Peter,Hansen, Lars Kristian,Andersson, Pher G.
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p. 2995 - 3001
(2007/10/03)
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- Asymmetrie hydrogenation of imines and olefins using phosphine-oxazoline iridium complexes as catalysts
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Herein we describe the synthesis of a new class of chiral phosphine-oxazolines and their application as ligands in iridium-catalyzed hydrogenations. Mechanistic aspects of olefin hydrogenation with this class of iridium catalysts are discussed and a selec
- Trifonova, Anna,Diesen, Jarle S.,Andersson, Pher G.
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p. 2318 - 2328
(2008/02/03)
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- Borrowing hydrogen: Indirect "Wittig" olefination for the formation of C-C bonds from alcohols
-
The successful development of an indirect three-step domino sequence for the formation of C-C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C-C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C-C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Black, Phillip J.,Edwards, Michael G.,Williams, Jonathan M. J.
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p. 4367 - 4378
(2007/10/03)
-
- Synthesis and enzymatic resolution of Cα-dialkylated α-azido carboxamides: New enantiopure α-azido acids as building blocks in peptide synthesis
-
α-Azido carboxylic acids have recently emerged as versatile N-protected equivalents for α-amino acids, especially valuable when the sterically hindered Cα-dialkylated α-amino acids have to be incorporated. Unsymmetrically substituted Cα/s
- Jost, Micha,Sonke, Theo,Kaptein, Bernard,Broxterman, Quirinus B.,Sewald, Norbert
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p. 272 - 278
(2007/10/03)
-
- Ring expansion-annulation strategy for the synthesis of substituted azulenes and oligoazulenes. 2. Synthesis of azulenyl halides, sulfonates, and azulenylmetal compounds and their application in transition-metal-mediated coupling reactions
-
A "ring expansion-annulation strategy" for the synthesis of substituted azulenes is described based on the reaction of β'-bromo- α-diazo ketones with rhodium carboxylates. The key transformation involves an intramolecular Buechner reaction followed by β-elimination of bromide, tautomerization, and in situ trapping of the resulting 1-hydroxyazulene as a carboxylate or triflate ester. Further synthetic elaboration of the azulenyl halide and sulfonate annulation products can be achieved by employing Heck, Negishi, Stille, and Suzuki coupling reactions. Reaction of the azulenyl triflate 84 with pinacolborane provides access to the azulenylboronate 91, which participates in Suzuki coupling reactions with alkenyl and aryl iodides. The application of these coupling reactions to the synthesis of biazulenes, terazulene 101, and related oligoazulenes is described, as well as the preparation of the azulenyl amino acid derivative 110.
- Crombie, Aimee L.,Kane Jr., John L.,Shea, Kevin M.,Danheiser, Rick L.
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p. 8652 - 8667
(2007/10/03)
-
- 5,5-Dimethyl-1,4,2-dioxazoles as versatile aprotic hydroxamic acid protecting groups
-
5,5-Dimethyl-1,4,2-dioxazoles are readily installed by transketalization of 2,2-diethoxypropane, where both the NH and OH moieties are protected in a nonprotic form. The dioxazoles are stable to a wide variety of reaction conditions and readily revert back to the hydroxamic acid by treatment with Nafion-H in 2-propanol. The method is applicable to primary, secondary, tertiary, and aromatic hydroxamic acids, and the acidity of the protons adjacent to the dioxazole allows α-functionalization.
- Couturier, Michel,Tucker, John L.,Proulx, Caroline,Boucher, Ghislain,Dube, Pascal,Andresen, Brian M.,Ghosh, Arun
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p. 4833 - 4838
(2007/10/03)
-
- Reduction of ethyl t-cinnamates by samarium diiodide
-
Rate constants directly measured from the GC-analyzed method for SmI2 reduction of ethyl t-cinnamate and its substituted derivatives in the presence of HMPA and t-butanol were obtained. HMPA exhibits a stronger catalytic effect than t-butanol. Dependence of reaction rates on concentration of SmI2 and temperature were studied. Electron-donating groups retard this reduction; the electron-withdrawing groups, on the other hand, enhance the reaction rates dramatically.
- Lin, Tzuen-Yeuan,Fuh, Ming-Ren,Chan, I-San
-
p. 843 - 847
(2007/10/03)
-
- Conjugate addition of arylsilanes to unsaturated carbonyl compounds catalyzed by rhodium in air and water
-
ArSiCl3 and Ar2SiCl2, believed to be unstable in aqueous media, reacted efficiently with α,β-unsaturated ketones and esters in air and water (in the presence of sodium fluoride and a rhodium catalyst), giving good to excellent yields of the desired conjugate addition products.
- Huang,Li
-
p. 2348 - 2349
(2007/10/03)
-
- A ring expansion-annulation strategy for the synthesis of substituted azulenes. Preparation and suzuki coupling reactions of 1-azulenyl triflates
-
(matrix presented) A new strategy for the synthesis of substituted azulenes is reported, based on the reaction of β′-bromo-α-diazo ketones with rhodium carboxylates The key transformation involves intramolecular addition of a rhodium carbenoid to an arene π-bond, electrocyclic ring opening, β-elimination, tautomerization, and trapping to produce 1-hydroxyazulene derivatives. The synthetic utility of the method is enhanced by the ability of the triflate derivatives to participate in Suzuki coupling reactions, as illustrated in a synthesis of the antiulcer drug egualen sodium (KT1-32).
- John L Jr., Kane,Shea, Kevin M.,Crombie, Aimee L.,Danheiser, Rick L.
-
p. 1081 - 1084
(2007/10/03)
-
- Enantiomerically pure cyclopropyl hemiacetals: Lipase-catalyzed synthesis of chiral, nonracemic ester homoenolate equivalents
-
equation presented Enantiomerically pure cyclopropyl hemiacetals can be obtained by lipase-catalyzed kinetic resolution of their acylated congeners. It is demonstrated that lipases from Candida antarctica and Pseudomonas cepacia show enantiodivergent beha
- Westermann, Bernhard,Krebs, Birte
-
p. 189 - 191
(2007/10/03)
-
- Ynenol Lactones: Synthesis and Investigation of Reactions Relevant to Their Inactivation of Serine Proteases
-
The syntheses of ynenol lactones which are designed as serine protease suicide substrates have b
- Spencer, Robin W.,Tam, Tim Fat,Thomas, Everton,Robinson, Valerie J.,Krantz, Allen
-
p. 5589 - 5597
(2007/10/02)
-
- YNENOLACTONE PROTEASE INHIBITORS
-
Compounds of the formula STR1 wherein n is 1-3; R 1, R. sup.2 and R 3 are the same or different and are hydrogen, lower alkyl, lower alkenyl, lower alkynyl, aryl or aryl lower alkyl wherein when aryl is phenyl it is unsubstituted or independently substituted with one or more halo, lower alkyl or lower alkoxy groups; and R 4 is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, trialkylsilyl, aryl or aryl lower alkyl wherein when aryl is phenyl it is unsubstituted or independently substituted by one or more halo, lower alkyl or lower alkoxy groups; excluding those compounds wherein R. sup.1 and R 2 are hydrogen and R 4 is ethyl, propyl or butyl. These compounds are useful as protease inhibitors.
- -
-
-
- 2-Methyl-1-phenyl-1-propenyllithium. A Vinyllithium Derivative Showing Catalyzed Transmetalation
-
Full preparative and kinetic details are given for the apparent vinyl-to-allyl anion rearrangement of the title compound 1.The rapid and quantitative formation of the allyllithium derivative 7 is shown to be catalyzed by 2-methyl-1-phenyl-1-propene (2).An intermolecular transmetalation mechanism with de-aggregation and ionization steps is suggested to explain the orders of reaction, parameters of activation, and solvent dependency.
- Knorr, Rudolf,Lattke, Ernst
-
p. 2116 - 2131
(2007/10/02)
-
- Synthesis of Carboxylic Acids and Esters Using Polymer-Bound Oxazolines
-
2,4-Dimethyl-4-(hydroxymethyl)-2-oxazoline was attached to cross-linked polystyrene, giving the polymer-bound oxazoline 3.Alkylation of 3, followed by hydrolysis or ethanolysis, provided α and α,α' mono- and dialkylated acetic acids or their ethyl esters
- Colwell, Arthur R.,Duckwall, Louis R.,Brooks, Reda,McManus, Samuel P.
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p. 3097 - 3102
(2007/10/02)
-
- Friedel-Crafts Reactions of Ethyl Cyclopropanecarboxylate
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The reaction of ethyl cyclopropanecarboxylate with benzene in the presence of aluminum chloride gives 2-methyl-1-indanone in excellent yield.
- Pinnick, Harold W.,Brown, Stephen P.,McLean, Elizabeth A.,Zoller, Linwood W.
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p. 3758 - 3760
(2007/10/02)
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