共查询到20条相似文献,搜索用时 375 毫秒
1.
Thermolysis of [ arachno-4-SB 8H 12] (1) in boiling cyclohexane gives two isomers 2 and 3 of 18-vertex [S 2B 16H 16], together with known 12-vertex [ closo-1-SB 11H 11] (4) and known 11-vertex [ nido-7-SB 10H 12] (5). Compounds 2 and 3 are characterised by single-crystal X-ray diffraction analyses and single- and double-resonance 11B- and 1H-NMR spectroscopy. The [ n-S 2B 16H 16] isomer 2 takes the form of nido ten-vertex: nido ten-vertex [ anti-B 18H 22] with the 9 and 9′ positions occupied by S vertices, whereas the [ iso-S 2B 16H 16] isomer 3 takes the form of a nido 11-vertex {SB 10} subcluster fused via a common two-boron edge to a nido-type {B 8} subcluster that is additionally linked exo to the {SB 10} subcluster by a bridging S atom that is held endo to the {B 8} unit. Isomer 2 is readily deprotonated and its monoanion 6 is characterised by NMR spectroscopy and by a single-crystal X-ray diffraction analysis of its [tmndH] +[ n-S 2B 16H 15] salt 6b; deprotonation has occurred from an open-face B---H---B bridging site. 相似文献
2.
Effects of sintering atmospheres on properties of SrCo 0.4Fe 0.5Zr 0.1O 3−δ mixed-conducting membranes were in detail studied in terms of sintering behavior, electrical conductivity and oxygen permeability. The sintering atmospheres were 100% N 2, 79% N 2–21% O 2, 60% N 2–40% O 2, 40% N 2–60% O 2, 20% N 2–80% O 2 and 100% O 2 (in vol.%), and the prepared membranes were correspondingly denoted as S-0, S-21, S-40, S-60, S-80 and S-100, respectively. It was found that the properties of membranes were strongly dependent on the sintering atmosphere. As the oxygen partial pressure in the sintering atmosphere ( PO2) increased, sintering ability, electrical conductivity and oxygen permeability decreased at first, which was in the order of S-0 > S-21 > S-40. However, as PO2 increased further, sintering ability, electrical conductivity and oxygen permeability increased gradually: S-40 < S-60 < S-80 < S-100. And the S-100 membrane had the best sintering ability, electrical conductivity and oxygen permeability in all membranes. 相似文献
3.
In situ reaction of Li[ closo-1-Ph-1,2-C 2B 10H 10] with 7-azabicyclo [4.1.0] heptane results in the formation of the disubstituted carborane, closo-1-Ph-2-(2′-aminocyclohexyl)-1,2-C 2B 10H 10 (1), in 63% yield. Decapitation of (1) with potassium hydroxide in refluxing ethanol produces the cage-opened nido-carborane, K[ nido-7-Ph-8-(2′-aminocyclohexyl)-7,8-C 2B 9H 10] − (2), in 80% yield. Deprotonation of the above monoanion with two equivalents of n-butyllithium followed by reaction with anhydrous MCl 4 · 2THF (M = Zr, Ti) provides d0-half-sandwich metallocarboranes, closo-1-M(Cl)-2-Ph-3-(2′- σ-(H) N-cyclohexyl)-2,3- η5-C 2B 9H 9 (3 M = Zr; 4 M = Ti) in 53% and 42% yields, respectively. The reaction of Li[ closo-1,2-C 2B 10H 11] with 7-azabicyclo [4.1.0] heptane in THF affords closo-1-(2′-aminocyclohexyl)-1,2-C 2B 10H 10 (5) in 59% yield. Immobilization of the carboranyl amino ligand (1) to an organic support, Merrifield’s peptide resin (1%), has been achieved by the reaction of the sodium salt of (5) with polystyryl chloride in THF to produce closo-1-(2′-aminocyclohexyl)-2-polystyryl-1,2-C 2B 10H 10 (6) in 87% yield. Further reaction of the dianion derived from (6) with anhydrous ZrCl 4 · 2THF led to the formation of the organic polystyryl supported d0-half-sandwich metallocarborane, closo-1-Zr(Cl)-2-(2′- σ-(H) N-cyclohexyl)-3-polystyryl-2,3-η 5-C 2B 9H 9 (7), in 38% yield. These new compounds have been characterized by elemental analyses, NMR, and IR spectra. Polymerizations of both ethylene and vinyl chloride with (3) and (7) have been performed in toluene using MMAO-7 (13% ISOPAR-E) as the co-catalyst. Molecular weights up to 32.8 × 10 3 ( Mw/ Mn = 1.8) and 9.5 × 10 3 ( Mw/ Mn = 2.1) were obtained for PE and PVC, respectively. 相似文献
4.
Reaction of the activated mixture of Re 2(CO) 10, Me 3NO and MeOH with a 1:1 mixture of rac ( d/ l)- and meso-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (hptpd) yields a mixture of ( d/ l)- and meso-[{Re 2(μ-OMe) 2(CO) 6} 2(μ,μ′-hptpd)] 1. The diastereomers can be easily separated by selective dissolution of d/ l-1 in benzene, and give clearly distinguishable 1H- and 31P-NMR spectra. The fluxional behavior of d/ l-1 in solution has been studied by variable-temperature 1H- and 31P-{ 1H}-NMR spectroscopy. The crystal structures of both d/ l- and meso-1 have been determined. Both molecules consist of two {Re 2(μ-OMe) 2(CO) 6} moieties which are bridged by the two P---CH 2---CH 2---P moieties of the hptpd ligand. Whilst the molecules of meso-1 possess crystallographic i-symmetry, those of d/ l-1 do not have any crystallographic symmetry. These diastereomers therefore give clearly distinguishable Raman spectra in the solid state. Reaction of tris[2-(diphenylphosphino)ethyl]phosphine (tdppep) with the activated mixture affords the complex [{Re 2(μ-OMe) 2(CO) 6}(μ,η 2-tdppep)] 2, and the analogous reaction involving bis[2-diphenylphospinoethyl)phenylphosphine (triphos) gives [{Re 2(μ-OMe) 2(CO) 6}(μ,μ′,η 3-triphos){Re 2(CO) 9}] 3 and [{Re 2(μ-OMe) 2(CO) 6}(μ,η 2-triphos)] 4. 相似文献
5.
In contrast to both its parent “troika” acid ( E-1, a phosphorylating agent at pH 7 and 25 °C) and its C-methyl isomer ( E-2, which is stable at both acidic and neutral pH), ( E)-(hydroxyimino)(hydroxymethoxyphosphinyl)acetic acid E-3 was unreactive at pH 7 and 25 °C but at pH 1.5 fragmented to methyl phosphate 10 (15%) and methyl phosphorocyanidate 11 (85%). The minor product is consistent with solvent phosphorylalion, the reaction exclusively observed with E-1. The non-phosphorylating fragmentation pathway is proposed to involve a preliminary E→ Z isomerizalion of 3 prior to C -C β cleavage. Dual fragmentation pathways were also detected ( 31P NMR) when the DCHA + salt of E-3 ( E-9) was heated in acetonitrile or EtOH; in addition to phosphorylation products (16–19%), 11 was formed (81–84%). Reaction of E-9 in refluxing EtOH: t-BuOH (1:1) showed low stereoselectivity in product formation (~3:1 ethyl methyl phosphate: t-butyl methyl phosphate), supporting a dissociative phosphorylation process. 相似文献
6.
Structures of the following compounds have been obtained: N-(2-pyridyl)- N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2 1/ c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) Å 3 and Z=4; N-2-(3-picolyl)- N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/ c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) Å 3 and Z=8; N-2-(4-picolyl)- N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2 1/ a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) Å 3 and Z=4; N-2-(5-picolyl)- N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/ c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) Å 3 and Z=8; N-2-(6-picolyl)- N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2 1/ c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) Å 3 and Z=4 and N-2-(4,6-lutidyl)- N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2 1/ c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) Å 3 and Z=4. Comparisons with other N-2-pyridyl- N′-arylthioureas having substituents in the 2-position of the aryl ring are included. 相似文献
7.
endo-Dicyclopentadiene (1) can be metalated by use of simple procedures with good overall yields. The attack occurs at the various vinyl, rather than at the allyl, positions of 1 as was confirmed by trapping the carbanions with Me 3SnCl. When t-BuLi/TMEDA are used, the 8- and 9-stannyl derivatives (3 and 4) are formed, whereas an excess of n-BuLi/t-BuOK leads to doubly stannylated derivatives with Me 3Sn groups in position 4/8 (6), 4/9 (7), and 3/9 (8) in addition to 3 and 4. Furthermore the latter reaction yields 5,5-bis(trimethylstannyl)cyclopentadiene (5). With stoichiometric amounts of n-BuLi/t-BuOK the formation of 3 and 4 predominates over that of 5–8. 5 is obtained from 1 after deprotonation at the allyl position, followed by an extremely fast retro-Diels-Alder reaction and then by further deprotonation. This follows from two experiments: (1) exo- and endo-5-trimethylstannyl- endo-dicyclopentadiene (11 and 12) which are synthesized from 1 in three steps give cyclopentadienyllithium and 1 when treated with methyllithium at −78°C; (2) cyclopentadiene reacts with an excess of n-BuLi/t-BuOK and Me 3SnCl to give 5. When 12 is heated syn-10-trimethylstannyl- endo-dicyclopentadiene (13) is obtained. The eight stannyl derivatives of 1 are identified mainly from the following NMR parameters: δ( 119Sn), δ( 13C), δ( 1H), nJ( 119/117Sn--- 13C), and 6J( 119Sn--- 119/117Sn). The 13C NMR satellite spectrum of 1 yields the isotope shifts 1Δ 13( i( 13C( j)) and 1J( 13C--- 13C). The latter lead to the revision of earlier signal assignments. 相似文献
8.
Reduction of trans-1-oxo-7-methoxy-1,2,3,4,9,10,11,12-octahydrophenanthrene (XI) by lithium tri-t-butoxyaluminohydride gave trans-1β-hydroxy-7-methoxy-1,2,3,4,9,10,11,12-octahydrophenanthrene (XII) which on lithium—liquid ammonia reduction gave trans-anti-1β-hydroxy-7-oxo-Δ 8(14)-dodecahydrophenanthrene (XIII). Reduction of cis-1-oxo-7-methoxy-1,2,3,4,9,10,11,12-octahydrophenanthrene (XV) by sodium borohydride gave cis-1-hydroxy-7-methoxy-1,2,3,4,9,10,11,12-octahydrophenanthrene (XVI) which on lithium—liquid ammonia reduction gave cis-syn-1-hydroxy-7-oxo-Δ 8(14)-dodecahydrophenanthrene (XVII). 相似文献
9.
The molecular and crystal structure of the nido-6-tungstadecaborane [6,6,6,6-(CO) 2(PPh 3) 2- nido-6-WB 9H 13] (1) has been determined showing that the tungsten atom is incorporated into the 6-position of a nido 10-vertex (WB 9) cage. The tungsten atom has a seven-coordinate capped trigonal prismatic environment and is bonded to two hydrogen and three boron atoms of the {B 9H 13} cage, in addition to two CO groups and two PPh 3 ligands. Variable-temperature (−90°C to +50°C) 31P{ 1H} NMR spectroscopy of 1 reveals that the exo-polyhedral ligands about the tungsten atom are fluxional with respect to PPh 3 site exchange with an activation energy (Δ G‡), at the coalescence temperature (−73°C), of <38 kJ mol −1. 相似文献
10.
Native and three selectively methylated β-cyclodextrin (β-CD)-bonded stationary phases without an unreacted spacer arm for liquid chromatography were prepared, where heptakis(2- O-methyl)-β-CD, heptakis(3- O-methyl)-β-CD and heptakis(2,3-di- O-methyl)-β-CD were used as the methylated β-CDs. The enantiomer separation abilities of the resulting β-CD stationary phases for 12 pairs of dansylamino acid enantiomers and six pairs of N-3,5-dinitrobenzoyl amino acid methyl esters as model solutes were investigated. The effects of pH and methanol content of the mobile phase on the retention and resolution were examined to optimize the mobile phase conditions. The optimum resolution for the dansylamino acids was achieved using a mobile phase consisting of 1.0% triethylammonium acetate buffer (pH 5.0)–methanol (v/v 4/6) on the β-CD stationary phase. Heptakis(3- O-methyl)- and heptakis(2,3-di- O-methyl)-β-CD-bonded stationary phases showed little enantiomer separation abilities for the dansylamino acids. The heptakis(2- O-methyl)-β-CD-bonded stationary phase exhibited no enantioselectivities for those solutes. For the N-3,5-dinitrobenzoyl amino acid methyl esters, the optimum resolution was achieved using a mobile phase consisting of 1.0% triethylammonium acetate buffer (pH 5.0)–methanol (v/v 9/1) on a heptakis(2-O-methyl)-β-CD stationary phase. The heptakis(2,3-di-O-methyl)-β-CD-bonded stationary phases exhibited no enantioselectivities for the N-3,5-dinitrobenzoyl amino acid methyl esters. β-CD and heptakis(3-O-methyl)-β-CD-bonded stationary phases had no enantiomer separation abilities for those solutes except for the N-3,5-dinitrobenzoyl phenylalanine methyl ester. 相似文献
11.
The reactions of RNHSi(Me) 2Cl (1, R= t-Bu; 2, R=2,6-(Me 2CH) 2C 6H 3) with the carborane ligands, nido-1-Na(C 4H 8O)-2,3-(SiMe 3) 2-2,3-C 2B 4H 5 (3) and Li[ closo-1-R′-1,2-C 2B 10H 10] (4), produced two kinds of neutral ligand precursors, nido-5-[Si(Me) 2N(H)R]-2,3-(SiMe 3) 2-2,3-C 2B 4H 5, (5, R= t-Bu) and closo-1-R′-2-[Si(Me) 2N(H)R]-1,2-C 2B 10H 10 (6, R= t-Bu, R′=Ph; 7, R=2,6-(Me 2CH) 2C 6H 3, R′=H), in 85, 92, and 95% yields, respectively. Treatment of closo-2-[Si(Me) 2NH(2,6-(Me 2CH) 2C 6H 3)]-1,2-C 2B 10H 11 (7) with three equivalents of freshly cut sodium metal in the presence of naphthalene produced the corresponding cage-opened sodium salt of the “carbons apart” carborane trianion, [ nido-3-{Si(Me) 2N(2,6-(Me 2CH) 2C 6H 3)}-1,3-C 2B 10H 11] 3− (8) in almost quantitative yield. The reaction of the trianion, 8, with anhydrous MCl 4 (M=Ti and Zr) in 1:1 molar ratio in dry tetrahydrofuran (THF) at −78 °C, resulted in the formation of the corresponding half-sandwich neutral d 0-metallacarborane, closo-1-M[(Cl)(THF) n]-2-[1′-η 1σ-N(2,6-(Me 2CH) 2C 6H 3)(Me) 2Si]-2,4-η 6-C 2B 10H 11 (M=Ti (9), n=0; M=Zr (10), n=1) in 47 and 36% yields, respectively. All compounds were characterized by elemental analysis, 1H-, 11B-, and 13C-NMR spectra and IR spectra. The carborane ligand, 7, was also characterized by single crystal X-ray diffraction. Compound 7 crystallizes in the monoclinic space group P2 1/ c with a=8.2357(19) Å, b=28.686(7) Å, c=9.921(2) Å; β=93.482(4)°; V=2339.5(9) Å 3, and Z=4. The final refinements of 7 converged at R=0.0736; wR=0.1494; GOF=1.372 for observed reflections. 相似文献
12.
13C and 31P{ 1H} NMR data at low temperature prompted us to characterize cis-[Rh(CO) 2(PR 3)Cl] (3) (3a, PR 3 = PPh 3; 3b, PR 3 = PMe 2Ph), as surprisingly stable products of the reaction between [{Rh(CO) 2(μ-Cl)} 2] (1) and tertiary phosphines in toluene (P : Rh = 1). Every attempt to isolate solid 3a led to the cis- and trans- halide-bridged dimers [{Rh(CO) 2(μ-Cl)} 2] (5a) and 6a which are formed from 3a by slow decarbonylation, a process which is greatly accelerated by the evaporation of the solvent under vacuum. The analogous reaction of 1 with dimethylphenylphosphine follows a similar pathway; in this case, however, low temperature NMR spectra allowed us to characterize the pentacoordinated dinuclear species [{Rh(CO)2(μ-Cl)}2] (2b) as the unstable intermediate of the bridge-splitting process. The reaction of 3 with a second equivalent of phosphine (P : Rh = 2) leads, at room temperature, to the well known product trans-[Rh(CO)(PR3)2Cl] (8) accompanied by evolution of CO; however our data show that when the reaction is performed at 200 K, decarbonylation is prevented and spectroscopic evidence of trigonal bipyramidal pentacoordinate [Rh(CO)2(PR3)2Cl] (7), stable only at low temperature, can be obtained. 相似文献
13.
For a closed-shell MO configuration with 2 n electrons which occupy n non-degenerate canonical MOs, it is deduced that the RHF energy, Σ ni=1[2 H0n+Σ nj-1(2 Jij-K ij)], may be expressed in Hückel-like form as 2Σ ni-1ε, −Σ ni-1[ ji(λ+1)+1,(λ+2)] with λ=2( n- i). The l i(λ+1) and Ii(λ+2) are the ionization potentials for the HOMO ψ, which arises after λ and λ+1 electrons have been successively removed from the initial configuration. 相似文献
14.
The π-allyltricarbonyliron lactone complex (7), formed by reaction of E-1,2-epoxy-2-methyl-6,6-dimethoxyhex-3-ene(5) with co-ordinatively unsaturated iron carbonyl species, was reacted with benzylamine to give a lactam complex (8) by an S N'-like mechanism. This complex upon oxidation with Ce(IV) afforded cis-3-isopropenyl-4-[(2',2'-dim (9) which was chemically modified into trans-3-(1'-hydroxyethyl)-4-[(2',2-dimethoxy)ethyl] azetidin-2-one (13), a key intermediate previously used in the synthesis of the antibiotic thienamycin. Similar reaction with ( S)-(-)--methylbenzylamine afforded a separable mixture of diastereoisomeric iron lactam complexes (16 and 17). These complexes could be individually converted to the corresponding optically active β-lactam derivatives (27 and 28) and, hence, are precursors for the synthesis of either natural (+)-thienamycin or unnatural (-)-thienamycin. 相似文献
15.
Reaction of phenyl magnesium bromide with the ,β-unsaturated ketone 3-methyl-2,3,4,5,6,7-hexahydroind-8(9)-en-1-one, followed by an aqueous work-up, generates the pro-chiral tetra-substituted cyclopentadiene, 1-phenyl-3-methyl-4,5,6,7-tetrahydroindene, Cp ‡H, a precursor to the η 5-cyclopentadienyl ligand in (Cp ‡) 2Fe and [(Cp ‡)Fe(CO)] 2(μ-CO) 2. Both complexes were generated as mixtures of rac-( RR and SS)- and meso-( RS)-isomers, and in either case pure meso-isomer was isolated by crystallisation and characterised by single crystal X-ray structure, both molecules having crystallographic Ci symmetry. Reduction with Na/Hg cleaves meso-( RS)-[(Cp ‡)Fe(CO)] 2(μ-CO) 2 and the resulting mixture of ( R)- and ( S)-[(Cp ‡)Fe(CO) 2] − anions reacts with MeI to give racemic (Cp ‡)Fe(CO) 2Me, which was characterised by the X-ray crystal structure. The Cp ‡ ligand is more electron donating than (η-C 5H 5) as revealed by the reduction potential of the (Cp ‡) 2Fe +/(Cp ‡) 2Fe couple, E°=−0.127 V (vs. Ag AgCl). Reaction of LiCp ‡ with ZrCl 4 yields the zirconocene dichloride [Zr(Cp ‡) 2Cl 2] as mixture of rac- and meso-isomers, from which pure rac-isomer is obtained as a mixture of RR and SS crystals by recrystallisation. The reaction of rac-[Zr(Cp ‡) 2Cl 2] with LiMe gives rac-[Zr(Cp ‡) 2Me 2]. The structures of RR-[Zr(Cp ‡) 2Cl 2] and rac-[Zr(Cp ‡) 2Me 2] have been determined by X-ray diffraction. The structural studies reveal the influence of the bulky substituted cyclopentadienyl ligand on the metal---Cp ‡ distances and other metric parameters. 相似文献
16.
N-2-(4-picolyl)- N′-2-chlorophenylthiourea, 4PicTu2Cl, monoclinic, P2 1/ c, a=10.068(5), b=11.715(2),
β=96.88(4)°,
and Z=4; N-2-(6-picolyl)- N′-2-chlorophenylthiourea, 6PicTu2Cl, triclinic, P-1, a=7.4250(8), b=7.5690(16), c=12.664(3) Å, =105.706(17), β=103.181(13), γ=90.063(13)°, V=665.6(2) Å 3 and Z=2 and N-2-(6-picolyl)- N′-2-bromophenylthiourea, 6PicTu2Br, triclinic, P-1, a=7.512(4), b=7.535(6), c=12.575(4) Å, a=103.14(3), β=105.67(3), γ=90.28(4)°, V=665.7(2) Å 3 and Z=2. The intramolecular hydrogen bonding between N′H and the pyridine nitrogen and intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen, as well as the planarity of the molecules, are affected by the position of the methyl substituent on the pyridine ring. The enthalpies of fusion and melting points of these thioureas are also affected. 1H NMR studies in CDCl 3 show the NH′ hydrogen resonance considerably downfield from other resonances in their spectra. 相似文献
17.
A new series of rigid-rod alkynylferrocenyl precursors with central fluoren-9-one bridge, 2-bromo-7-(2-ferrocenylethynyl)fluoren-9-one (1b), 2-trimethylsilylethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (2) and 2-ethynyl-7-(2-ferrocenylethynyl)fluoren-9-one (3), have been prepared in moderate to good yields. The ferrocenylacetylene complex 3 can provide a direct access to novel heterometallic complexes, trans-[(η 5-C 5H 5)Fe(η 5-C 5H 4)CCRCCPt(PEt 3) 2Ph] (4), trans-[(η 5-C 5H 5)Fe(η 5-C 5H 4)CCRCCPt(PBu 3) 2CCRCC(η 5-C 5H 4)Fe(η 5-C 5H 5)] (5), [(η 5-C 5H 5)Fe(η 5-C 5H 4)CCRCCAu(PPh 3)] (6) and [(η 5-C 5H 5)Fe(η 5-C 5H 4)CCRCCHgMe] (7) (R=fluoren-9-one-2,7-diyl), following the CuI-catalyzed dehydrohalogenation reactions with the appropriate metal chloride compounds. All the new complexes have been characterized by FTIR, 1H-NMR and UV–vis spectroscopies and fast atom bombardment mass spectrometry. The solid state molecular structures of 3, 5, 6 and 7 have been established by X-ray crystallography. The redox chemistry of these mixed-metal species has been investigated by cyclic voltammetry and oxidation of the ferrocenyl moiety is facilitated by the presence of the heavy metal centre and increased conjugation in the chain through the ethynyl and fluorenone linkage units. 相似文献
18.
Acylrhodium(III)-η 3-1-ethylallyl complex (7) was prepared by the reaction of 8-quinolinecarboxaldehyde (3) and 1,4-pentadienerhodium(I) chloride (2) by C---H bond activation, followed by hydrometallation, and double bond migration. Higher concentrations of pyridine as coordinating ligand transforms η 3-1-ethylallylrhodium(III) complexes (8a,8b) into η 1-pent-2-enylrhodium(III) complex (11a). Acylrhodium(III)-η 3- syn,anti-1,3-dimethylallyl complex (14) was also prepared from 1,3-pentadienerhodium(I) chloride (16) and 3. The reductive elimination of acylrhodium(III)-η 1- and -η 3-1-alkylallyl complexes by trimethylphosphite gives various β,γ-unsaturated ketones. 相似文献
19.
Optically active nitroalkenes 4 were synthesized via Henry reaction. Conjugate addition of vinylmagnesium bromide to 4 gave nitroalkane syn-5 while cyclopropanation with sulfur ylides or dibromocarbene afforded nitrocyclopropanes 8, 10 and 11 in a diastereoselective manner. These products were used to synthesize optically active β-amino acids 7 and 16 as well as cyclopropane γ-amino acids 19 and 20 by reduction of the nitro group and oxidative cleavage of the dioxolane substituent. 相似文献
20.
Vinyl substituted (1 R,2 S)-amino alcohols 5 were obtained by addition of vinyl magnesium bromide to the corresponding cyanohydrin O-trimethylsilyl ethers ( R)-2. The O- and N-protected vinyl amino alcohols 6 were ozonized at −78°C in methanol yielding (1 R,2 S)-2-amino-1,3-diols7 in high enantiomeric and diastereomeric excesses. For purification, compounds 7 in some cases were acetylated to give the derivatives (1 R,2 S)-8. Racemic 6a was converted by oxidative ozonolysis at −78°C in methanolic NaOH solution to the corresponding methyl N-acetyl-β-hydroxy propanoate 9a. The configuration of (1 R,2 S)-8 a was confirmed by x-ray crystallographic analysis. 相似文献
|