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1.
The four isomeric 5, 10-pentadecadienals 1 , 2 , 3 and 4 were prepared by stereo-selective routes from acetylenic precursors. Two of them, 2 and 4 , were also made by Wittig reaction from 2-hydroxytetrahydropyran (29) . 2-Hydroxytetrahydropyran (29) yields (Z)-5-alkenols efficiently by Wittig reaction, and (Z)-4-hexenol was similarly made from 2-hydroxytetrahydrofuran (66) .  相似文献   

2.
The structures of [Cu(2-Brbz)2(4PM)2(H2O)] (1) and [Cu(2-Brbz)2(NIA)2] · 2H2O 2 [where 2-Brbz is the 2-bromobenzoate anion, 4-PM is the 4-pyridylmethanol and NIA is nicotinamide] have been determined by X-ray and characterized by EPR spectroscopy. The Cu2+ cation in 1 is coordinated by a pair of oxygens from monodentate 2-bromobenzoate anions by a pair of pyridine nitrogens from monodentate 4-pyridylmethanol ligands and finally by a water forming a tetragonal-pyramidal coordination polyhedron. The Cu2+ cation in 2 is coordinated by two pairs of oxygens from the asymmetric bidentate 2-bromobenzoate anions and by a pair of pyridine nitrogen atoms from the monodentate nicotinamide in trans positions, forming an extremely elongated bipyramid. The molecules of both complexes are linked by O–H ··· O, C–H ··· O and for 2 by N–H ··· O hydrogen bonds, which create three-dimensional hydrogen-bonding networks. EPR spectra of 1 and 2 are in agreement with X-ray data. Nicotinamide as well as 4-pyridylmethanol are suitable ligands for construction of hydrogen bonding coordination polymers.  相似文献   

3.
The crystal and molecular structure of [Cu(nif)2(4-PM)2]·CH3OH (1) and [Cu(2-Clbz)2(4-PM)2(H2O)] (2), (where nif = niflumate anion, 2-Clbz = 2-chlorobenzoate anion and 4-PM is the 4-pyridylmethanol), have been determinated by X-ray crystallography. The Cu2+ cation in (1), is coordinated by two pairs of oxygen atoms from asymmetric bidentate niflumate anions and by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands in trans position forming an extremely elongated bipyramid. The Cu2+ cation in (2), is coordinated by a pair of oxygen atoms from monodentate 2-chlorobenzoate anions, further by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands and finally by a water oxygen atom forming a tetragonal-pyramidal coordination polyhedron. The molecules of both complexes in crystal structures are linked by O-H…O hydrogen bonds, which created a three-dimensional hydrogen-bonding networks. The Π-Π stacking interactions are also observed in crystal structures of complex 2. The spectral properties (IR and electronic spectra) of both complexes were also investigated.  相似文献   

4.
5-Propionyl-2-thiophene aldehyde, mp 101–101. 5°, is synthesized by two routes, from 2-propiothienone, and from 2-thiophene aldehyde, and its structure is confirmed by oxidation to 5-propionyl-2-thiophene carboxylic acid and thiophene-2, 5-dicarboxylic acid. The fact that 2-acetals and 2-ketals of the thiophene series are metallated only at position 5 in the ring by n-butyllithium is confirmed. Attempts to synthesize 5-propionyl-2-thiophene aldehyde by a method given by Janda and Dvorak [1, 2] were unsuccessful.  相似文献   

5.
Expulsion of CO2 from the molecular ions of the 2-(2-carboxyphenyl) derivatives of benzoxazole, benzothiazole and benzimidazole gives rise to the base peaks on electron impact. The proposed mechanism for this fragmentation process, involving the anchimeric assistance of the heteroatom by the initial abstraction of the H˙ from the carboxyl group followed by the expulsion of CO2 from the molecular ions, is supported by the study of the linked scan spectra.  相似文献   

6.
Vijay Singh  Sanjay Batra 《Tetrahedron》2006,62(43):10100-10110
The formation of substituted 2-pyrrolidinones and indoles by the reduction of the secondary nitro group in appropriate 3-aryl-2-methylene-4-nitroalkanoates afforded by Baylis-Hillman chemistry via different reducing agents is described. The 3-aryl-2-methylene-4-nitroalkanoate obtained from SN2 nucleophilic reaction between the acetate of Baylis-Hillman adducts and ethyl nitroacetate upon reduction with indium-HCl furnishes a mixture of cis and trans substituted phenyl-3-methylene-2-pyrrolidinones. In contrast, similar reductions of analogous substrates derived from nitroethane stereoselectively furnished only the trans substituted phenyl-3-methylene-2-pyrrolidinones. On the other hand the SnCl2·2H2O-promoted reductions of substrates derived from nitro ethylacetate give oxime derivatives while the ones obtained from nitroethane yield a mixture of cis and trans 4-aryl-3-methylene-2-pyrrolidinones. Alternatively, the SnCl2·2H2O-promoted reduction of substituted 2-nitrophenyl-2-methylene-alkanoate furnished from ethyl nitroacetate yield 3-(1-alkoxycarbonyl-vinyl)-1H-indole-2-carboxylate while indium-promoted reaction of this substrate leads to a complex mixture. Analogous reactions with SnCl2·2H2O of substituted 2-nitrophenyl-2-methylene-alkanoate obtained from nitroethane yield 4-alkyl-3-methylene-2-quinolones in moderate yields.  相似文献   

7.
Crystal Packings with Linearly Coordinated Atoms Formally, crystal structures containing linearly coordinated atoms can be derived from simple structure types in various ways. In a systematic way, this can be done with the aid of crystallographic group‐subgroup relationships. One way is shown for K2HgO2 and KAgO, the structures of which result from the NaCl type by vacating certain Cl positions. Another way is the expansion of a crystal packing in order to obtain linearly coordinated atoms from octahedral coordination. This way, α‐HgO2 results from the pyrite type, HgBr2 and HgI2 from SnS2‐4H, HgCl2 from diaspore (AlOOH), and HgO from NaCl. Na2PdC2 results from the NiAs type, when half of the Ni atoms are substituted by acetylide groups and the structure is expanded perpendicular to c . A third procedure is to formally insert an atom between two adjacent atoms, such as the insertion of O atoms between the metal atoms of the polonium structure to obtain the ReO3 structure. Insertion of Au atoms into the NaCl type results in the KAuS structure, and insertion of Cu atoms between O atoms of anatase results in the SrCu2O2 type. Further insertion products are LiAg3O2 (Ag inserted in the SiS2 type) and NaHgPO4 (Hg inserted in the CrVO4 type). Insertion of atoms between spheres of the body‐centered cubic structure yields the structures of PtHg4, Cu2O, AuCl and CS2. Insertion of Cu atoms into the O—O bonds of β‐O2 and simultaneous occupation of the octahedral voids with Fe atoms results in the delafossite structure (FeCuO2), which is also adopted by oxide‐hydroxides like CrOHO and by LiFHF and NaN3. Insertion of Hg atoms between the chalcogen atoms of the α‐Se structure results in the cinnabar structure (HgS); however, due to the widening of the spiral chains, the S atoms then adopt a different packing, and the structure is more adequately described by a hexagonal sphere packing of spheres having coordination number 10 and Hg atoms occupying certain voids. The quartz structure can also be derived from this sphere packing (of Si atoms) by inserting O atoms.  相似文献   

8.
New copper complexes with two structural isomeric ligands, 2-(indazol-1-yl)-2-thiazoline (TnInA) and 2-(indazol-2-yl)-2-thiazoline (TnInL), have been synthesized and characterized by magnetic measurements, IR, electronic and EPR spectroscopies. Moreover, the molecular structures of [Cu(NO3)(TnInA)2(H2O)](NO3) · (H2O) (1) and [Cu(NO3)2(TnInL)(H2O)] (2) have been resolved by single-crystal X-ray diffraction studies. In compound 1 the copper ion is in a distorted octahedral geometry, with the equatorial plane formed by four nitrogen donor atoms from two organic ligands and the axial positions occupied by two oxygen atoms from a water molecule and a mono-coordinated nitrate anion. The coordination geometry around the copper atom in compound 2 can be described basically as a square pyramid with two nitrogen atoms from TnInL ligand, one oxygen atom from a water molecule and one oxygen atom from a nitrate group in the equatorial plane. The axial position is occupied by one oxygen atom from a nitrate group. Likewise, a second oxygen atom from the last nitrate group in equatorial position might involve in a weak sixth coordination position to give a (4 + 1 + 1) coordination mode.  相似文献   

9.
4-Acetylbenzoxazolin-2(3H)-one has been prepared biomimetically during attempts to synthesize the hemiacetalic hydroxamic acid 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one by the immediate degradation of this unstable compound generated as an intermediate. Thus, 4-acetylbenzoxazolin-2(3H)-one recently isolated from Zea mays kernels, and similar to other benzoxazolin-2(3H)-ones known from plant sources, is assumed to have originated from the degradation of natural 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one which in turn could have been enzymatically released by a β-glucosidase from the corresponding 2-β-D-glucoside.  相似文献   

10.
A previously unknown transformation of aldehydes, ketones, and carboxylic acid derivatives leads to the formation of substituted oxiranes, aziridines, and azirines as shown by DFT and MP2 computations. Formations of 2,2-dimethyloxirane-d8 from acetone-d6, phenylazirine-d2 from benzonitrile and 2-methyl-2-(4-hydroxyphenyl)-oxirane from 4-hydroxyacetophenone were detected experimentally by electrospray ionization mass-spectrometry with a heated desolvating capillary. This reaction is a truly concerted process characterized by high activation barriers (activation enthalpies 320–480 kJ mol−1).  相似文献   

11.
The photochemical reactions of α,β-acetylenic ketones have been examined. Irradiation of 1-p-substituted phenyl-2-propyn-1-ones 2–4 in primary alcohols gave 2,5-disubstituted furans 2a–4c. The formation of furans can be explained in terms of cyclization, followed by dehydration of the 1:1-adduct of acetylenic ketone and alcohol, which was formed initially by hydrogen atom abstraction from alcohol by the excited acetylenic ketone. Irradiation of 1-p-tolyl-2-propyn-1-one ( 2 ) in ethanol-d1 yielded 2-methyl-5-p-tolylfuran ( 2b ) containing no deuterium. This result was consistent with a mechanism that involves hydrogen atom abstraction from alcohol by the carbon of triple bond rather than abstraction by carbonyl oxygen.  相似文献   

12.
The MÖSSBAUER spectra of various samples of differently prepared SnII and SnIV iodides have been investigated. — An SnI2 sample, prepared by dissolving elemental tin in hydroiodic acid, was shown to be strongly contamined with SnI4; by recrystallisation from ethanol no purification was achieved. However, SnI2 samples being free from SnI4 were obtained by precipitation from SnCl2 solutions by means of HI, KI or NaI. The isomeric shift value of SnI2 is 3.8 mm/sec. — SnI4 may be easily prepared from metallic tin and elemental iodine in CHCl3 or py precipitation from an SnCl4 solution by means of HI or KI.  相似文献   

13.
The adsorption of Pb(II) ions from aqueous solutions by chitosan flakes and beads was studied. The chitosan beads were prepared by casting an acidic chitosan solution into alkaline solution. Experiments were carried out as a function of pH, agitation period and initial concentration of Pb2+ ions. The uptake of Pb2+ ions from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The maximum uptake of Pb2+ ions on chitosan beads was greater than that on chitosan flakes. Adsorption isothermal data could be interpreted by the Langmuir equation. The experimental data of the adsorption equilibrium from Pb2+ ion solutions correlated well with the Langmuir isotherm equation. SEM analyses were also conducted for visual examination of the chitosan flakes and beads. Physical properties including surface area and average pore diameter were characterized by N2 adsorption experiment.  相似文献   

14.
A variety of optically active 2‐hydroxyalkanoates and the corresponding 2‐acyloxyalkanoates are produced by the kinetic resolution of racemic 2‐hydroxyalkanoates by using achiral 2,2‐diarylacetic acid with hindered carboxylic anhydrides as the coupling reagents. The combined use of diphenylacetic acid, pivalic anhydride, and (+)‐(R)‐benzotetramisole ((R)‐BTM) effectively produces (S)‐2‐hydroxyalkanoates and (R)‐2‐acyloxyalkanoates from the racemic 2‐hydroxyalkanoates (s‐values=47–202). This protocol directly provides the desired chiral 2‐hydroxyalkanoate derivatives from achiral diarylacetic acid and racemic secondary alcohols that do not include the sec‐phenethyl alcohol moiety by using the transacylation process to generate the mixed anhydrides from the acid components with bulky carboxylic anhydrides under the influence of the chiral acyl‐transfer catalyst. The transition state that provides the desired (R)‐2‐acyloxyalkanoate from (R)‐2‐hydroxyalkanoate included in the racemic mixture is disclosed by DFT calculations, and the structural features of the transition form are also discussed.  相似文献   

15.
2‐Amino‐1,2,3,4‐tetrahydronaphthalene‐6,7‐diol ( 2 ; 6,7‐ADTN) was synthesized starting from naphthalene‐2,3‐diol in seven steps and with an overall yield of 44%. Methylation of naphthalene‐2,3‐diol with dimethyl sulfate, followed by Friedel? Crafts acylation with AcCl, gave 2‐acetyl‐6,7‐dimethoxynaphthalene. 2‐Acetyl‐6,7‐dimethoxynaphthalene was converted to 6,7‐dimethoxynaphthalene‐2‐carboxylic acid by a haloform reaction. Birch reduction of the carboxylic acid with 4 mol‐equiv. of Na in liquid ammonia afforded 1,2,3,4‐tetrahydro‐6,7‐dimethoxynaphthalene‐2‐carboxylic acid, from which 2 was obtained by a Curtius reaction, followed by hydrogenolysis and demethylation.  相似文献   

16.
杨金会  孟丽聪 《有机化学》2008,28(5):918-921
1,3-二-(2-羟基-4-甲氧基苯基)丙烷(1)和1,3-二-(2,4-二羟基苯基)丙烷(2)是从菊叶薯蓣(Dioscorea composita Hemsl.)分离出来的天然产物, 以间苯二酚为起始原料, 分别经甲酰化和乙酰化得到2,4-二羟基苯甲醛和2,4-二羟基苯乙酮, 然后经选择性地甲基化、甲氧甲基化、羟醛缩合、还原、脱保护等步骤完成了上述两种天然产物的首次全合成. 产物通过1H NMR, IR, MS进行了结构确证.  相似文献   

17.
The structure of the polycrystalline adduct bis(diethyldithiocarbamato)-pyridine zinc(II) depends on the pathway of physico-chemical conditions during the preparation procedure, as was revealed by solid state 15N CP/MAS spectroscopy in good correlation with known single crystal X-ray diffraction structures of this adduct. Two isomorphs of the adduct, namely α-[Zn(Py)(S2CNEt2)2] and β-[Zn(Py)(S2CNEt2)2], are the two molecules in the asymmetric unit of a single crystal (or polycrystalline) sample that can be obtained by recrystallization from toluene of the equimolar solution of the initial diethyldithiocarbamate zinc(II) complex and pyridine. The third isomorph, γ-[Zn(Py)(S2CNEt2)2], can be obtained by recrystallization from pure pyridine of the diethyldithiocarbamate zinc(II) complex, or by its equimolar absorption of pyridine, or by desorption of pyridine from the clathrated adduct, [Zn(Py)(S2CNEt2)2]·Py. Finally, the γ-[Zn(Py)(S2CNEt2)2] isomorph recrystallizes from the melt into α/β-isomorphs of the adduct.  相似文献   

18.
Fragmentations of the carboxyl group are not generally observed from molecular anions produced by the capture of slow electrons. Enhancement of the internal energy of the molecular anions by collision excitation allows the detection of the fragmentations of the substituent in the field free regions of the mass spectrometer. Fragmentations include the losses of CO2 or ·CO2H from molecular anions, and the elimination of CO2 from fragment ions.  相似文献   

19.
The photocatalytic evolution of H2 from ethanol and aqueous solutions of Na2SO3 and Na2S by suspensions of CdS/Cu2+ and CdS/Bi3+ microheterojunctions has been investigated. The appearance of autocatalysis has been obtained, attributed to a lowering of the energy barrier of the reaction; it is caused by a change in the work function of an electron from the palladium co-catalyst, due to its saturation by the product (hydrogen).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 5, pp. 435–440, September–October, 1993.  相似文献   

20.
The D2 loss from C2D+6 ions and the HD loss from C2D5H+ ions has been investigated in a photoelectron photoion coincidence experiment employing a reflecting ion time of a flight mass spectrometer (Reflectron). The experiment is able to distinguish the metastable formation of C2D+4 ions (m/z = 32) from C2D+6 ions by D2 loss and from C2D5H+ ions by HD loss simultaneously in a mixture of deuterated ethanes. The breakdown curves of the title reactions are presented and compared to the H2 loss from C2H+6 ions. The HD loss from C2D5H+ is shifted by 67 meV and the D2 loss from C2D+6 is shifted by 108 meV with respect to the H2 loss from C2H+6. This shift reflects a strong kinetic isotope effect which is most likely due to tunneling of H/D atoms through a barrier.  相似文献   

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