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1.
Halogenation of the potassium or silver salts of bis((trifluoromethyl)sulfonyl)methane(CF3SO2)2CH2 and its cyclo analogues (CF2)nSO2‐CH2SO2CF2 with N‐fluoro‐bis((trifluoromethyl)sul‐fonyl)imine (CF3SO2)2NF, chlorine or bromine gave good yields of the corresponding α‐halo disulfones (CF3SO2)2CHX and (CF2)nSO2CHXSO2CF2 (X: F, Cl, Br; n = 1,2). Some chemical transformations of these fluorinated α‐halo‐disulfones are described. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 147–151, 1999  相似文献   

2.
Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral CuII/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β‐amino alcohol derivatives.  相似文献   

3.
α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CXn (n=1–2, X=Cl, Br) or a H?CAr bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX2 interaction.  相似文献   

4.
A AgF‐mediated fluorination with a concomitant cross‐coupling between a gem‐difluoroolefin and a non‐fluorinated olefin is reported. This highly efficient method provides facile access to both α‐CF3 alkenes and β‐CF3 ketones, which otherwise remain challenging to be directly prepared. The application of this method is further demonstrated by the synthesis of bioactive isoxazoline derivatives. This approach represents a conceptually novel route to trifluoromethylated compounds that combines the in situ generation of the CF3 moiety and a C? H functionalization in a single reaction system.  相似文献   

5.
A stereospecific synthesis of (2S)3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph3P catalyzed reaction of the latter with C2Cl6 followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield.  相似文献   

6.
Catalytic enantioselective α‐fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α‐fluorinated carbonyl compounds. Nevertheless, α‐fluorination of α‐nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α‐hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3‐(2‐naphthyl)‐l ‐alanine‐derived amides are highly effective catalysts for the enantio‐ and site‐selective α‐fluorination of N‐(α‐arylacetyl) and N‐(α‐alkylacetyl) 3,5‐dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α‐fluorinated α‐amino acid derivative). α‐Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield.  相似文献   

7.
The Oshima? Nozaki (Et2AlI) condensation of isolevoglucosenone ( 4 ) with 2,6‐anhydro‐3,4,5,7‐tetra‐O‐benzyl‐D ‐glycero‐D ‐gulo‐heptose ( 5 ) gave an enone 6 that was converted with high stereoselectivity to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐2,3‐dideoxy‐D ‐arabino‐hexose ( 1 ; 1 : 1 mixture of α‐ and β‐D ‐pyranose), and to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐2,3‐dideoxy‐D ‐lyxo‐hexose ( 2 ; 2.7 : 1.4 : 1.0 : 1.4 mixture of α‐D ‐furanose, β‐D ‐furanose, α‐D ‐pyranose, and β‐D ‐pyranose). The Oshima? Nozaki (Et2AlI) condensation of levoglucosenone ( 17 ) with aldehyde 5 gave an enone 18 that was converted with high stereoselectivity to 3‐C‐[(1R)‐2,6‐anhydro‐D ‐glycero‐D ‐gulo‐heptitol‐1‐C‐yl]‐3,4‐dideoxy‐α‐D ‐arabino‐hexopyranose ( 3 ; single anomer).  相似文献   

8.
Starting from methyl 2,3‐O‐isopropylidene‐α‐D ‐mannofuranoside ( 5 ), methyl 6‐O‐benzyl‐2,3‐O‐isopropylidene‐α‐D ‐lyxo‐hexofuranosid‐5‐ulose ( 12 ) was prepared in three steps. The addition reaction of dimethyl phosphonate to 12 , followed by deoxygenation of 5‐OH group, provided the 5‐deoxy‐5‐dimethoxyphosphinyl‐α‐D ‐mannofuranoside derivative 15a and the β‐L ‐gulofuranoside isomer 15b . Reduction of 15a and 15b with sodium dihydrobis(2‐methoxyethoxy)aluminate, followed by the action of HCl and then H2O2, afforded the D ‐mannopyranose ( 17 ) and L ‐gulopyranose analog 21 , each having a phosphinyl group in the hemiacetal ring. These were converted to the corresponding 1,2,3,4,6‐penta‐O‐acetyl‐5‐methoxyphosphinyl derivatives 19 and 23 , respectively, structures and conformations (4C1 or 1C4, resp.) of which were established by 1H‐NMR spectroscopy.  相似文献   

9.
As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C16H14F6N2O2, contains the smallest fluorinated group, viz. CF3. The molecule resides on a crystallographic inversion centre at the mid‐point of the pyridine Cipso—Cipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C—H...N and C—H...O interactions are observed, similar to those in related polyfluorinated bpy–metal complexes. A π–π interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C—H...N hydrogen bonding is present between one of the CF3CH2– methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl‐type C—H...F interactions to atoms of the terminal CF3 group. It is of note that the O—CH2CF3 bond is almost perpendicular to the bpy plane.  相似文献   

10.
The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C15H26O12·H2O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ~0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ~16°) than for ? (Δ = ~6°).  相似文献   

11.
A catalytic and stereoselective glycosylation of several glycosyl acceptors with β‐D ‐glycosyl fluoride was successfully performed in the presence of a catalytic amount of trityl tetrakis(pentafluorophenyl)borate (TrB(C6F5)4) or trifluoromethanesulfonic acid (TfOH). When TrB(C6F5)4 was used as a catalyst in the solvent pivalonitrile/(trifluoromethyl)benzene 1 : 5, the glycosylation proceeded smoothly to afford the glycosides in high yields with high β‐D ‐stereoselectivities (see Table 3). Further, the glycosylation by the armed‐disarmed strategy in the presence of this catalyst was established (see Table 4). Similarly, glycosylation catalyzed by the strong protic acid TfOH afforded the corresponding β‐D ‐glycosides in good‐to‐excellent yields on treating β‐D ‐ glycosyl fluorides having a 2‐O‐benzoyl group with various glycosyl acceptors including thioglycosides (see Tables 6 and 7).  相似文献   

12.
Six 4‐alkyl‐4‐azaheptane‐1,7‐diamines, characterized as their solid bis(D ‐gluconamides), were prepared in a two‐step synthesis: bis(cyanoethylation) of the primary alkylamines (C8–C18, even‐numbered) followed by an efficient lithium aluminum hydride reduction of the resulting bisnitriles. The azadiamines were then used as monomers in condensation polymerizations with methyl D ‐glucarate 1,4‐lactone in a methanol solution, yielding polyhydroxypolyaminopolyamides isolated directly as white solids with varying hydrophobic/hydrophilic character. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3892–3899, 2000  相似文献   

13.
The polyfluorinated title compounds, [MBr2(C18H16F8N2O2)] or [4,4′‐(HCF2CF2CH2OCH2)2‐2,2′‐bpy]MBr2, ( 1 ) (M = Pd and bpy is bipyridine) and ( 2 ) (M = Pt), have –CH(α)2OCH(β)2CF2CF2H side chains with methylene H‐atom donors at the α and β sites, and methine H‐atom donors at the terminal sites, in addition to aromatic H‐atom donors. In contrast to the original expectation of isomorphous structures, ( 1 ) crystallizes in the space group C2/c and ( 2 ) in P21/n, with similar unit‐cell volumes and Z = 4. The asymmetric unit of ( 1 ) is one half of the molecule, which resides on a crystallographic twofold axis. Both ( 1 ) and ( 2 ) display stacking of the molecules, indicating a planar (bpy)MBr2 skeleton in each case. The structure of ( 1 ) exhibits columns with C—H(β)…Br hydrogen bonds between consecutive layers which conforms to a static (β,β) linkage between layers. In the molecular plane, ( 1 ) shows double C—H(α)…Br hydrogen bonds self‐repeating along the b axis, the planar molecules being connected into infinite belts. Compound ( 2 ) has no crystallographic symmetry and forms π‐dimer pairs as supermolecules, which then stack parallel to the a axis. The π‐dimer‐pair supermolecules exhibit (Pt—)Br…Br(—Pt) contacts [3.6937 (7) Å] to neighbouring π‐dimer pairs crosslinking the columns. The structure of ( 2 ) reveals many C—H…F(—C) interactions between F atoms and aromatic C—H groups, in addition to those between F atoms and methylene C—H groups.  相似文献   

14.
The migratory insertions of cis or trans olefins CH(X)?CH(Me) (X = Ph, Br, or Et) into the metal–acyl bond of the complex [Pd(Me)(CO)(iPr2dab)]+ [B{3,5‐(CF3)2C6H3}4]? ( 1 ) (iPr2dab = 1,4‐diisopropyl‐1,4‐diazabuta‐1,3‐diene = N,N′‐(ethane‐1,2‐diylidene)bis[1‐methylethanamine]) are described (Scheme 1). The resulting five‐membered palladacycles were characterized by NMR spectroscopy and X‐ray analysis. Experimental data reveal some important aspects concerning the regio‐ and stereochemistry of the insertion process. In particular, the presence of a Ph or Br substituent at the alkene leads to the formation of highly regiospecific products. Moreover, in all cases, the geometry of the substituents in the formed palladacycle was the same as in the starting olefin, as a consequence of a cis addition of the Pd–acyl fragment to the C?C bond. Reaction with CO and MeOH of the five‐membered complex derived from trans‐β‐methylstyrene (= [(1E)‐prop‐1‐enyl]benzene) insertion, yielded the 2,3‐substituted γ‐keto ester 9 with an (2RS,3SR)‐configuration (Scheme 3).  相似文献   

15.
Methyl β‐d ‐galactopyranosyl‐(1→4)‐α‐d ‐mannopyranoside methanol 0.375‐solvate, C13H24O11·0.375CH3OH, (I), was crystallized from a methanol–ethanol solvent system in a glycosidic linkage conformation, with ϕ′ (O5Gal—C1Gal—O1Gal—C4Man) = −68.2 (3)° and ψ′ (C1Gal—O1Gal—C4Man—C5Man) = −123.9 (2)°, where the ring is defined by atoms O5/C1–C5 (monosaccharide numbering); C1 denotes the anomeric C atom and C6 the exocyclic hydroxymethyl C atom in the βGalp and αManp residues, respectively. The linkage conformation in (I) differs from that in crystalline methyl α‐lactoside [methyl β‐d ‐galactopyranosyl‐(1→4)‐α‐d ‐glucopyranoside], (II) [Pan, Noll & Serianni (2005). Acta Cryst. C 61 , o674–o677], where ϕ′ is −93.6° and ψ′ is −144.8°. An intermolecular hydrogen bond exists between O3Man and O5Gal in (I), similar to that between O3Glc and O5Gal in (II). The structures of (I) and (II) are also compared with those of their constituent residues, viz. methyl α‐d ‐mannopyranoside, methyl α‐d ‐glucopyranoside and methyl β‐d ‐galactopyranoside, revealing significant differences in the Cremer–Pople puckering parameters, exocyclic hydroxymethyl group conformations and intermolecular hydrogen‐bonding patterns.  相似文献   

16.
Mixtures of N‐alkyl pyridinium compounds [py‐N‐(CH2)nOC6H3‐3,5‐(OMe)2]+(X?) ( 1b Cl: n=10, X=Cl; 1c Br: n=12, X=Br) and α‐cyclodextrin (α‐CD) form supramolecular hydrogels in aqueous media. The concentrations of the two components influences the sol–gel transition temperature, which ranges from 7 to 67 °C. Washing the hydrogel with acetone or evaporation of water left the xerogel, and 13C CP/MAS NMR measurements, powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) revealed that the xerogel of 1b Cl (or 1c Br) and α‐CD was composed of pseudorotaxanes with high crystallinity. 13C{1H} and 1H NMR spectra of the gel revealed the detailed composition of the components. The gel from 1b Cl and α‐CD contains the corresponding [2]‐ and [3]pseudorotaxanes, [ 1b? (α‐CD)]Br and [ 1b? (α‐CD)2]Br, while that from 1c Br and α‐CD consists mainly of [3]pseudorotaxane [ 1c? (α‐CD)2]Br. 2D ROESY 1H NMR measurements suggested intermolecular contact of 3,5‐dimethoxyphenyl and pyridyl end groups of the axle component. The presence of the [3]pseudorotaxane is indispensable for gel formation. Thus, intermolecular interaction between the end groups of the axle component and that between α‐CDs of the [3]pseudorotaxane contribute to formation of the network. The supramolecular gels were transformed into sols by adding denaturing agents such as urea, C6H3‐1,3,5‐(OH)3, and [py‐NnBu]+(Cl?).  相似文献   

17.
We have unfolded a convenient and mild protocol for the synthesis of diaryl ketones via Pd‐ NHC catalysed carbonylative Suzuki coupling reaction. Notably, this method offers advantages like no use of toxic CO gas, shorter reaction time, high yield, and broad substrate scope. Several sensitive functional groups (like‐COMe, ‐COOMe, ‐F, ‐Cl, ‐Br, ‐NH2, ‐CN) are well tolerated in this reaction. In addition, we have also demonstrated a new efficient route for the synthesis of biologically active and pharmaceutically important 2‐substituted 3‐Aroylquinolin‐4(1H)‐ones and acridone scaffolds.  相似文献   

18.
The known glucaro‐1,5‐lactam 8 , its diastereoisomers 9 – 11 , and the tetrahydrotetrazolopyridine‐5‐carboxylates 12 – 14 were synthesised as potential inhibitors of β‐D ‐glucuronidases and α‐L ‐iduronidases. The known 2,3‐di‐O‐benzyl‐4,6‐O‐benzylidene‐D ‐galactose ( 16 ) was transformed into the D ‐galactaro‐ and L ‐altraro‐1,5‐lactams 9 and 11 via the galactono‐1,5‐lactam 21 in twelve steps and in an overall yield of 13 and 2%, respectively. A divergent strategy, starting from the known tartaric anhydride 41 , led to the D ‐glucaro‐1,5‐lactam 8 , D ‐galactaro‐1,5‐lactam 9 , L ‐idaro‐1,5‐lactam 10 , and L ‐altraro‐1,5‐lactam 11 in ten steps and in an overall yield of 4–20%. The anhydride 41 was transformed into the L ‐threuronate 46 . Olefination of 46 to the (E)‐ or (Z)‐alkene 47 or 48 followed by reagent‐ or substrate‐controlled dihydroxylation, lactonisation, azidation, reduction, and deprotection led to the lactams 8 – 11 . The tetrazoles 12 – 14 were prepared in an overall yield of 61–81% from the lactams 54, 28 , and 67 , respectively, by treatment with Tf2O and NaN3, followed by saponification, esterification, and hydrogenolysis. The lactams 8 – 11 and 40 and the tetrazoles 12 – 14 are medium‐to‐strong inhibitors of β‐D ‐glucuronidase from bovine liver. Only the L ‐ido‐configured lactam 10 (Ki = 94 μM ) and the tetrazole 14 (Ki = 1.3 mM ) inhibit human α‐L ‐iduronidase.  相似文献   

19.
Practical syntheses of 2‐keto‐3‐deoxy‐D ‐xylonate (D ‐KDX) and 2‐keto‐3‐deoxy‐L ‐arabinonate (L ‐KDA) that rely on reaction of the anion of ethyl 2‐[(tert‐butyldimethylsilyl)oxy]‐2‐(dimethoxy phosphoryl) acetate with enantiopure glyceraldehyde acetonide, followed by global deprotection of the resultant O‐silyl‐enol esters, have been developed. This has enabled us to confirm that a 2‐keto‐3‐deoxy‐D ‐gluconate aldolase from the archaeon Sulfolobus solfataricus demonstrates good activity for catalysis of the retro‐aldol cleavage of both these enantiomers to afford pyruvate and glycolaldehyde. The stereochemical promiscuity of this aldolase towards these enantiomeric aldol substrates confirms that this organism employs a metabolically promiscuous pathway to catabolise the C5‐sugars D ‐xylose and L ‐arabinose.  相似文献   

20.
Fluoroalkylsulfonyl chlorides, RfSO2Cl, in which Rf=CF3, C4F9, CF2H, CH2F, and CH2CF3, are used as a source of fluorinated radicals to add fluoroalkyl groups to electron‐deficient, unsaturated carbonyl compounds. Photochemical conditions, using Cu mediation, are used to produce the respective α‐chloro‐β‐fluoroalkylcarbonyl products in excellent yields through an atom transfer radical addition (ATRA) process. Facile nucleophilic replacement of the α‐chloro substituent is shown to lead to further diverse functionalization of the products.  相似文献   

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