- Asymmetric Aminations and Kinetic Resolution of Acyclic α-Branched Ynones
-
An efficient method for asymmetric synthesis of acyclic α-tertiary amine derivatives has been achieved through enantioselective aminations of α-branched ynones with azodicarboxylates enabled by chiral phosphoric acid catalysis. Moreover, kinetic resolution of racemic starting material was realized under these conditions, which gave access to valuable enantioenriched α-substituted ketones. A wide array of α-aryl and alkyl-substitutions, and the substituted alkynyl groups were well compatible with this method, producing both the amination products and the recovered ketones with good to high enantioselectivities.
- He, Faqian,Shen, Guosong,Yang, Xiaoyu
-
supporting information
p. 15 - 20
(2021/11/20)
-
- syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
-
Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
- Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
-
supporting information
p. 3604 - 3612
(2021/07/26)
-
- Palladium-Catalyzed Carbocyclizations of Unactivated Alkyl Bromides with Alkenes Involving Auto-tandem Catalysis
-
The development of a general catalytic system for the palladium-catalyzed carbocyclization of unactivated alkyl bromides with alkenes is described. This approach uses a commercially available bisphosphine ligand and avoids the use of carbon monoxide atmosphere present in prior studies involving alkyl iodides. Detailed mechanistic studies of the transformation are performed, which are consistent with auto-tandem catalysis involving atom-transfer radical cyclization followed by catalytic dehydrohalogenation. These studies also suggest that reactions involving alkyl iodides may proceed through a metal-initiated, rather than metal-catalyzed, radical chain process.
- Venning, Alexander R. O.,Kwiatkowski, Megan R.,Roque Pe?a, Joan E.,Lainhart, Brendan C.,Guruparan, Akil A.,Alexanian, Erik J.
-
supporting information
p. 11595 - 11600
(2017/08/30)
-
- IMMUNOREGULATORY AGENTS
-
Compounds that modulate the oxidoreductase enzyme indoleamine 2,3- dioxygenase, and compositions containing the compounds, are described herein. The use of such compounds and compositions for the treatment and/or prevention of a diverse array of diseases,
- -
-
Paragraph 0552
(2016/06/01)
-
- Development of an O-Vinylation-Ring-Closing Metathesis Strategy to Access 3,3′-3,4-Dihydropyrans
-
Dihydropyrans are common structural motifs that appear in both natural products and pharmaceuticals and are intermediates for the synthesis of tetrahydropyrans. Currently, no reports exist in the literature for the synthesis of 3,3′-differentially disubst
- Dechert-Schmitt, Anne-Marie,Cabral, Shawn,Kung, Daniel W.
-
supporting information
p. 2611 - 2615
(2016/11/11)
-
- Synthesis of α-aryl esters and nitriles: Deaminative coupling of α-aminoesters and α-aminoacetonitriles with arylboronic acids
-
Transition-metal-free synthesis of α-aryl esters and nitriles using arylboronic acids with α-aminoesters and α-aminoacetonitriles, respectively, as the starting materials has been developed. The reaction represents a rare case of converting C(sp3)-N bonds into C(sp3)-C(sp2) bonds. The reaction conditions are mild, demonstrate good functional-group tolerance, and can be scaled up. Touch base: A transition-metal-free protocol for the synthesis of α-aryl esters and nitriles by deaminative coupling is presented. Strong bases and transition-metal catalysts are not needed. The new synthetic method uses readily available starting materials and demonstrates wide substrate scope.
- Wu, Guojiao,Deng, Yifan,Wu, Chaoqiang,Zhang, Yan,Wang, Jianbo
-
supporting information
p. 10510 - 10514
(2016/02/18)
-
- Reactivity of terminal phenylpentenes in a ruthenium-catalyzed cross-metathesis reaction: Construction of linear bifunctional C-8 alkenes
-
In the present study the behavior of 1-functionalized 2-phenylpent-4-enes in the presence of ruthenium-based metathesis catalysts was investigated. The experimental observations revealed that the outcome of the reaction depends very much on the combination of olefinic partners used in the reaction; only certain combinations delivered satisfactory amounts of unsymmetrical cross-metathesis products, i.e., bifunctional C-8 alkenes.
- Stefane, Bogdan,Pozgan, Franc
-
p. 633 - 640
(2013/07/26)
-
- First iodine-catalyzed deallylation of reactive allyl methylene esters
-
C-Allyl cleavage has been developed using the inexpensive and mild reagent iodine in dimethylsulfoxide. A variety of compounds with active methylene groups were C-deallylated using this reagent. This method is efficient and operationally simple in comparison to the methods using transition-metal complexes. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Nawghare, Beena R.,Lokhande, Pradeep D.
-
p. 1955 - 1963
(2013/06/05)
-
- Carbon-carbon bond-forming reactions of α-carbonyl carbocations: Exploration of a reversed-polarity equivalent of enolate chemistry
-
Carbon-carbon bond-forming reactions of putative α-carbonyl carbocation intermediates generated by Lewis acid- or silver-promoted ionizations of toluenesulfonate or halide leaving groups are described. This under-exploited mode of reactivity represents an 'umpolung' of conventional enolate chemistry, and enables C-C bond construction in both intra- and intermolecular contexts. Attempts to develop diastereoselective variants of this process using chiral ester and oxazolidinone-based auxiliaries are discussed.
- Lai, Ping-Shan,Dubland, Joshua A.,Sarwar, Mohammed G.,Chudzinski, Michael G.,Taylor, Mark S.
-
p. 7586 - 7592
(2011/10/12)
-
- Evidence for a non-concerted, dissoziative mechanism of the palladium-catalyzed enolate Claisen rearrangement of allylic esters
-
In an enolate Claisen rearrangement, deprotonated allyl phenylacetate undergoes a smooth conversion at -78 °C to 2-phenyl-4-pentenoic acid under palladium(O) catalysis. By using labelled starting materials in crossover experiments, the reaction is shown to follow a dissoziative, non-concerted, non-[3,3]-sigmatropic mechanism that involves palladium complexes and carboxylic-acid dianions as intermediates.
- Braun, Manfred,Meletis, Panos,Schrader, Wolfgang
-
scheme or table
p. 5369 - 5372
(2010/11/18)
-
- Diastereoselective access to trans -2-substituted cyclopentylamines
-
A highly diastereoselective synthesis of trans-2-substituted cyclopentylamines via a tandem hydrozirconation/Lewis acid-mediated cyclization sequence applied to butenyl oxazolidines is described. The method allows an easy preparation of diversely substituted cyclopentylamines which appear to be useful synthetic intermediates. This was further illustrated by the syntheses of (±)-Rodocaine, (±)-trans-pentacin, and enantiomerically enriched trans-cyclopentane-1,2-diamine.
- Joosten, Antoine,Lambert, Emilie,Vasse, Jean-Luc,Szymoniak, Jan
-
supporting information; experimental part
p. 5128 - 5131
(2011/01/05)
-
- Trimethylsilyl triflate mediated new carbon-carbon bond forming reactions between benzyl diphenylphosphinates and organosilicon compounds
-
The trimethylsilyl triflate mediated reaction of benzyl diphenylphosphinate with allyltrimethylsilane or trimethylsilyl enolate afforded the corresponding cross-coupling products in good yields. Copyright
- Kobashi, Yohei,Minowa, Tomofumi,Mukaiyama, Teruaki
-
p. 756 - 757
(2007/10/03)
-
- Design of polyaromatic hydrocarbon-supported tin reagents: A new family of tin reagents easily removable from reaction mixtures
-
We report in this paper the preparation and use of stannanes 11, 12a, and 12b, compounds whose 3-pyrenylpropyl side chain affinity for activated carbon simplifies tin removal and product isolation. Our pyrene-supported reagents can be used for radical reductions and cyclizations (11), radical and cationic allylations (12a), and Stille couplings (12b) in much the same way as tributyltin derivatives.
- Stien, Didier,Gastaldi, Stephane
-
p. 4464 - 4470
(2007/10/03)
-
- Synthesis and structure-antifungal activity relationships of 3-aryl-5-alkyl-2,5-dihydrofuran-2-ones and their carbanalogues: Further refinement of tentative pharmacophore group
-
Two series of 3-(substituted phenyl)-5-alkyl-2,5-dihydrofuran-2-ones related to a natural product, (-)incrustoporine, were synthesized and their in vitro antifungal activity evaluated. The compounds with halogen substituents on the phenyl ring exhibited selective antifungal activity against the filamentous strains of Absidia corymbifera and Aspergillus fumigatus. On the other hand, the influence of the lenghth of the alkyl chain at C(5) was marginal. The antifungal effect of the most active compound against the above strains was higher than that of ketoconazole, and close to that of amphotericin B. In order to verify the hypothesis about a possible relationship between the Michael-accepting ability of the compounds and their antifungal activity, a series of simple carbanalogues, 2-(substituted phenyl)cyclopent-2-enones, was prepared and subjected to antifungal activity assay as well.
- Pour, Milan,Spulak, Marcel,Balsanek, Vojtech,Kunes, Jiri,Kubanova, Petra,Buchta, Vladimir
-
p. 2843 - 2866
(2007/10/03)
-
- Predominant 1,2-insertion of styrene in the Pd-catalyzed alternating copolymerization with carbon monoxide
-
The regioselectivity of styrene insertion to an acyl-Pd bond was studied by NMR in (i) a stoichiomeric reaction and (ii) a copolymerization with CO. In the stoichiometric reaction of styrene with [(CH3CO)Pd-(CH3CN){(R,S)-BINAPHOS}] ·[B{3,5-(CF3)2C6 H3}4], both 1,2-and 2,1-products were given. To mimic the real polymerization conditions, a polyketone-substituted complex [{CH3(CH2CHCH3CO)n}Pd{(R,S)-BINAP HOS}]·[B(3,5-(CF3)2C6 H3)4] (n ≈ 14) was prepared. When this polymer-attached Pd species was treated with styrene, the 1,2-insertion product was the only detectable species. Thus, exclusive 1,2-insertion is demonstrated to be responsible for the styrene-CO copolymerization, in sharp contrast to the predominant 2,1-insertion with conventional nitrogen ligands. Chain-end analysis revealed that β-hydride elimination took place from the 2,1-complex but not from the 1,2-complex. Thus, once 2,1-insertion occurs, rapid β-hydride elimination proceeds to terminate the polymerization, as is common to the other phosphorus-ligand systems. The resulting Pd-H species re-initiates the copolymerization, as was proven by MALDI-TOF mass analysis of the product copolymers.
- Nozaki,Komaki,Kawashima,Hiyama,Matsubara
-
p. 534 - 544
(2007/10/03)
-
- 3-Phenyl-5-methyl-2H,5H-furan-2-ones: Tuning antifungal activity by varying substituents on the phenyl ring
-
A series of racemic 3-phenyl-5-methyl-2H,5H-furan-2-ones related to a natural product, (-)incrustoporine, was synthesized, and their antifungal activity evaluated. The key structural feature, furanone ring, was closed via H2SO4-mediated cyclization of 2-phenylpent-4-enoic acids. The compounds displayed antifungal activity, especially against filamentous fungi. Expressed as the minimum inhibition concentration (MIC) in μmol/L, the activity of the most promising derivative against Absidia corymbifera matched that of ketoconazole (31.25 μmol/L). In terms of μg/mL, the substance was more active (7.6 μg/mL) than this standard antifungal drug (16.6 μg/mL). (C) 2000 Elsevier Science Ltd. All rights reserved.
- Pour, Milan,Spulak, Marcel,Balsanek, Vojtech,Kunes, Jiri,Buchta, Vladimir,Waisser, Karel
-
p. 1893 - 1895
(2007/10/03)
-
- Acid-catalyzed cyclization of vinylsilanes bearing a hydroxy group: A new method for stereoselective synthesis of disubstituted tetrahydrofurans
-
In the presence of a catalytic amount of TsOH or TiCl4, (Z)-5-silyl-4-penten-1-ols ((Z)-1) are smoothly cyclized to 2-silylmethyl-substituted tetrahydrofurans. This cyclization is applicable to the construction of a tetrahydropyran ring. The silyl group and the geometry of the C-C double bond strongly influence the cychzation rate. TBDMS and benzyldimethylsilyl groups considerably accelerate the cyclization in comparison with a dimethylphenylsilyl group, and (E)-vinylsilanes show much lower reactivity than the corresponding (Z)-isomers. The cyclization proceeds by stereospecific syn addition of the hydroxy group. Vinylsilanes 17, 19, and 21, (Z)-5-silyl-4-penten-1-ols bearing a substituent on the methylene tether, smoothly undergo the acid-catalyzed cyclization to give trans-2,5-, cis-2,4-, and trans-2,3-disubstituted tetrahydrofurans, respectively, with moderate to high stereoselectivity. The silyl group of some cychzed products can be easily converted into a hydroxy group with stereochemical retention.
- Miura,Okajima,Hondo,Nakagawa,Takahashi,Hosomi
-
p. 11348 - 11357
(2007/10/03)
-
- A practical new chiral controller for asymmetric Diels-Alder and alkylation reactions
-
(formula presented) The enantiomerically pure hydroxy sulfones (+)- and (-)-2 have been prepared from 1,2-epoxycyclohexane by a simple and practical procedure. The acrylate esters of these alcohols undergo BCl3-catalyzed Diels-Alder reactions with a variety of dienes at -78 to -55°C in CH2Cl2 or C7H8 with high dienophile face selectivity (Table 1). The chiral esters so formed are readily cleaved with recovery of the controllers (+)- or (-)-2. Esters of (+)- and (-)-2 can be converted to Z-polassium enolates and alkylated with high face selectivity.
- Sarakinos, Georgios,Corey
-
p. 1741 - 1744
(2008/02/11)
-
- The Stereochemistry of Ring Closure of Some Monosubstituted o-(But-3-enyl)phenyl Radicals
-
The rates and diastereoselectivity of cyclization of o-(but-3-enyl)phenyl radicals bearing substituents on the 1- or 2-position of the side chain have been examined. 1-Substituted radicals afford only 1,5-cyclization products, but 2-substituted radicals a
- Beckwith, Athelstan L. J.,Gerba, Sendaba
-
p. 289 - 308
(2007/10/02)
-
- Allylic Carbonates. Efficient Allylating Agents of Carbonucleophiles in Palladium-Catalyzed Reactions under Neutral Conditions
-
Allylation of β-keto esters or malonates was carried out in good yields under neutral conditions by using allylic carbonates in the presence of palladium-phospine catalyst.Although simple ketones, esters, nitriles, and sulfones hardly react with allylic carbonates, α-alkenyl or α-aryl ketones, esters, nitriles, and sulfones were also allylated by using palladium-bis(diphenylphosphino)ethane catalyst under neutral conditions.
- Tsuji, Jiro,Shimizu, Isao,Minami, Ichiro,Ohashi, Yukihiro,Sugiura, Teruo,Takahashi, Kazuhiko
-
p. 1523 - 1529
(2007/10/02)
-
- PALLADIUM-CATALYZED PREPARATION OF α-ALLYL ESTERS AND α,β-UNSATURATED ESTERS FROM SATURATED ESTERS VIA THEIR KETENE SILYL ACETALS
-
Reaction of ketene silyl acetals with allylic carbonates in the presence of palladium-phosphine catalyst in dioxane gives α-allyl esters in high yields.When the reaction is carried out with phosphine-free palladium catalyst in nitriles, α,β-unsaturated esters are obtained in good yields.
- Tsuji, Jiro,Takahashi, Kazuhiro,Minami, Ichiro,Shimizu, Isao
-
p. 4783 - 4786
(2007/10/02)
-