Attempted Synthesis of the Imidazylate of an α-Hydroxylactone Results in Unexpected Chlorination: Synthesis and X-Ray Crystal Structure of 5-Chloro-5-deoxy-1,2-O-isopropylidene-β-l-idurono-6,3-lactone

Attempted synthesis of the imidazylate derivative of 1,2-O-isopropylidene-α-D-glucurono-6,3-lactone (2) via treatment with sulfuryl chloride in the presence of excess imidazole in DMF at either –40°C or –70°C resulted in the unexpected formation of 5-chloro-5-deoxy-1,2-O-isopropylidene-β-l-idurono-6,3-lactone (7). Chloride 7 presumably forms via the rapid S_N2 displacement by a chloride ion of an initially formed chlorosulfate ester intermediate, which is evidently unusually reactive. The identity of the product was confirmed by a single-crystal X-ray structure determination.     

Fluxional rearrangement in congested ruthenium(II) complexes containing pyrimidine- and/or pyridine-based dithioether ligands

The solvento species obtained by the treatment of cis-RuCl₂(N,N-L)₂ [L = di-2-pyridyl sulfide (dps), di-2-pyrimidyl sulfide (dprs)] with AgPF₆, reacted with dithioethers L′ [L′ = 2,6-bis(2-pyridylthiomethyl)pyridine (pytmp), 2,6-bis(2-pyrimidylthiomethyl)pyridine (prtmp) and 2,6-bis{2-(4-methyl)pyrimidylthiomethyl} pyridine (mprtmp)] to afford the compounds [Ru(N,N-L)₂(N,S-L′)][PF₆]₂. The ¹H NMR spectra indicate that L′ is chelated through S and N atoms with the formation of a four-membered ring. As a consequence, the ruthenium and sulfur atoms are stereogenic centers with ∆ and Λ and (R) and (S) configurations, respectively. NMR spectra, at low temperatures, show that two invertomers, of similar abundance, as enantiomeric couples ∆S, ΛR and ∆R, ΛS are present. In the methylene region, four AB systems are observed that in both the species contain two non-equivalent methylene groups. Variable-temperature NMR spectra and EXSY experiments show that the sulfur inversion produces an exchange between the invertomers. The one-dimensional band-shape analysis of the exchanging methylene signals showed that the energy barriers for the process are in the 43–52 kJ mol⁻¹ range. The possible mechanisms of the sulfur inversion are discussed.     

The First C 3-Symmetric P-Stereogenic Diphosphinomethane Trinuclear Palladium Clusters: Synthesis and Characterization

The enantiomeric ligands (R,R)- and (S,S)-bis(o-anisylphenylphosphino)methane (R,R-14 and S,S-14, respectively) were used to prepare the C ₃-point group clusters [Pd₃(dppm*)₃(CO)(O₂CCF₃)](CF₃CO₂) with dppm* = (R,R)-14 or (S,S)-14. The chiral structure of an enantiomeric clusters (with the chiral R,R-ligand (R,R)-14) was unambiguously demonstrated by both X-ray structure determination and by circular dichroism spectroscopy. This paper is dedicated to Professor C.N.R. Rao.     

Über 4-Alkylamino-bzw. 4-Arylamino-5,6-dihydro-2(1H)-pyridinthione

Heating 1-alkyl- or 1-aryldihydro-6-methyl-2(1H)-pyrimidinethiones5, 6 in an inert medium causes rearrangement to 4-alkylamino-(4-arylamino-)-5,6-dihydro-2(1H)-pyridinethiones11, 12, probably via the methylene form29, by thermal heterolysis of the N₁/C₂ bond and exchange of the alkylamino (arylamino) group 1 through the carbon atom of the methylene group 6. The aminodihydropyridinethiones11, which can be regarded as cyclic derivatives of 3-aminothiocrotonamide, react with bistrichlorophenylmalonate under diacylation, and with formaldehyde and primary amines to yield aminodialkylation products of the enamine system, tetrahydro-4-hydroxy-7,7-dimethyl-5-thioxopyrido[4,3-b]pyridine-2(1H)-ones13, 14 and hexahydro-7,7-dimethylpyrido[4,3-d]pyrimidine-5(6H)-thiones18, 19, 21 respectively. H₂O₂ converts11 to the corresponding 4-aminodihydro-2(1H)-pyridones22, which can be reconverted into11 with P₄S₁₀.11 reacts with alkyl halides to 2-alkylthiodihydropyridines23, 24, 25. The mechanism of the methylpyrimidine-pyridine rearrangement is discussed.     

Asymmetric Synthesis of Highly Enantiomerically Enriched (S)(-)-β-Bisabolene

(S)-β-Bisabolene, (S)-1, was synthetized by a synthetic route in which (S)-4-methyl-3-cyclohexene carboxylic acid, (S)-10, which was the key intermediate, was prepared via a highly diastereoselective TiCl₄-catalyzed Diels-Alder reaction between isoprene and the acrylate of commercial (R)-pantolactone, followed by hydrolysis. Compound (S)-10 was then converted into ketone (S)-13 using two different procedures. The best one of these, as regards the degree of stereospecificity, involved the reaction of (S)-10 with 2 equiv of 4-methyl-3-penten-1-yllithium, 14, in the presence of CeCl₃, and gave (S)-13 having ca. 84% ee. The Zr-promoted methylenation of this ketone afforded highly enantiomerically enriched (S)-1.     

über 4-Alkylamino-bzw. 4-Arylamino-5,6-dihydro-2(1H)-pyridinthione

Heating 1-alkyl- or 1-aryldihydro-6-methyl-2(1H)-pyrimidinethiones5, 6 in an inert medium causes rearrangement to 4-alkylamino-(4-arylamino-)-5,6-dihydro-2(1H)-pyridinethiones11, 12, probably via the methylene form29, by thermal heterolysis of the N₁/C₂ bond and exchange of the alkylamino (arylamino) group 1 through the carbon atom of the methylene group 6. The aminodihydropyridinethiones11, which can be regarded as cyclic derivatives of 3-aminothiocrotonamide, react with bistrichlorophenylmalonate under diacylation, and with formaldehyde and primary amines to yield aminodialkylation products of the enamine system, tetrahydro-4-hydroxy-7,7-dimethyl-5-thioxopyrido[4,3-b]pyridine-2(1H)-ones13, 14 and hexahydro-7,7-dimethylpyrido[4,3-d]pyrimidine-5(6H)-thiones18, 19, 21 respectively. H₂O₂ converts11 to the corresponding 4-aminodihydro-2(1H)-pyridones22, which can be reconverted into11 with P₄S₁₀.11 reacts with alkyl halides to 2-alkylthiodihydropyridines23, 24, 25. The mechanism of the methylpyrimidine-pyridine rearrangement is discussed.     

Multifunctional coupling agents for living cationic polymerization. IV. Synthesis of end-functionalized multiarmed poly(vinyl ethers) with multifunctional silyl enol ethers

Telechelic ( 8 ) and end-functionalized four-arm star polymers ( 9 ) were synthesized through the coupling reactions of end-functionalized living poly(isobutyl vinyl ether) ( 5; DP _n ～ 10) with the bi-and tetrafunctional silyl enol ethers, H_4-nC? [CH₂OC₆H₄C(OSiMe₃) = CH₂]_n ( 3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH₃CH(Cl)OCH₂CH₂X(6), in conjunction with zinc chloride in methylene chloride at ?15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X , including acetoxy [? OC(O)CH₃], styryl (? OCH₂C₆H₄-p-CH = CH₂), and methacryloyl [? OC(O)C(CH₃) = CH₂]. The coupling reactions with 3 and 4 in methylene chloride at ?15°C for 24 h afforded the end-functionalized multiarmed polymers ( 8 and 9 ) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc.     

Synthesis and structural characterization of ruthenium complexes with 1-aryl-imidazole-2-thione

Treatment of [RuCl₂(PPh₃)₃] with 2 equiv. Himt^MPh (Himt^MPh?=?1-(4-methyl-phenyl)-imidazole-2-thione) in the presence of MeONa afforded cis-[Ru(κ ²-S,N-imt^MPh)₂(PPh₃)₂] (1), while interaction of [RuCl₂(PPh₃)₃] and 2 equiv. Himt^MPh in tetrahydrofuran (THF) without base gave [RuCl₂(κ ¹-S-Himt^MPh)₂(PPh₃)₂] (2). Treatment of [RuHCl(CO)(PPh₃)₃] with 1 equiv. Himt^MPh in THF gave [RuHCl(κ ¹-S-Himt^MPh)(CO)(PPh₃)₂] (3), whereas reaction of [RuHCl(CO)(PPh₃)₃] with 1 equiv. of the deprotonated [imt^MPh]^? or [imt^NPh]^? (imt^NPh?=?1-(4-nitro-phenyl)-2-mercaptoimidazolyl) gave [RuH(κ ²-S,N-imt^RPh)(CO)(PPh₃)₂] (R?=?M 4a, R?=?N 4b). The ruthenium hydride complexes 4a and 4b easily convert to their corresponding ruthenium chloride complexes [RuCl(κ ²-S,N-imt^MPh)(CO)(PPh₃)₂] (5a) and [RuCl(κ ²-S,N-imt^NPh)(CO)(PPh₃)₂] (5b), respectively, in refluxing CHCl₃ by chloride substitution of the RuH. Photolysis of 5a in CHCl₃ at room temperature afforded an oxidized product [RuCl₂(κ ²-S,N-imt^MPh)(PPh₃)₂] (6). Reaction of 6 with excess [imt^MPh]^? afforded 1. The molecular structures of 1·EtOH, 3·C₆H₁₄, 4b·0.25CH₃COCH₃, and 6·2CH₂Cl₂ have been determined by single-crystal X-ray crystallography.     

Dielectric relaxation of a short molecule in a liquid-crystalline solvent

Abstract

Dielectric relaxation measurements of 5 mole % 4-n-hexyloxycyanobenzene (I) dissolved in 4-n-pentyloxyphenyl-trans-4-n-octylcyclohexylcarboxylate (II) were carried out from 1 kHz to 10 MHz in the nematic, smectic A and smectic B phases. The relaxation frequency of I parallel to the director is about 05 MHz in the S_Bphase and increases rapidly at the transition from S_B to S_A.     

Hydrogen bonding or deprotonation: on fluoride ion fluorescence sensing with 1,1′-bi-2-naphthol derivatives

The isolation and structural characterisation of two ionic complexes (S)-3 and(S)-4 based on fluoride ion-mediated deprotonation of 1,1′-bi-2-naphthol (BINOL) derivatives (S)-1 and (S)-2 have been carried out for the first time. X-ray crystallographic study showed that the deprotonated forms (S)-3 and (S)-4 adopt remarkably different molecular geometries, bond parameters as well as molecular packing modes from their neutral analogs, in agreement with their significant fluorescence changes upon the addition of fluoride ion, giving insights into the actual mechanism of fluoride ion fluorescence sensing. The deprotonation–protonation processes in two BINOL derivatives were also investigated by both fluorescence measurements and X-ray structural analyses. Such chiral basic compounds can be promising organocatalysts for asymmetric reactions.     

Stereoselectivity in Reactions of Metal Complexes. Part XV. Structure and stability of chiral cobalt(III) complexes with pentadentate ligands

The syntheses and characterization of four new linear pentadentate ligands and their Co^III complexes are described: N,N′-[(pyridine-2,6-diy)bis(methylene)]bis[sarcosine] (sarmp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[(R)- or (S)-proline] ((R,R)- or (S,S)-promp), N,N′-[(pyridine-2,6-diyl)bis(methylene)]bis[N-(methyl)-(R)- or (S)-alanine] ((R,R)- or (S,S)-malmp); 2,2′-[pyridine-2,6-diyl]bis[(S)- or rac-N-(acetic acid)pyrrolidine] ((S,S)- or rac-bapap). The complexes were characterized and, with but one exception, complex formation is stereospecific: Δ-exo-(R,R) (or Λ-exo-(S,S)) for promp and Λ-(R,R) (or Δ-(S,S)) for bapap. The exception is [Co((R,R)- or (S,S)-malmp)H₂O]ClO₄ for which two forms are obtained, to which Λ-endo-(R,R) (or Δ-endo-(S,S)) and, tentatively, Δ-unsymmetric-(R,R)- (or Λ-unsymmetric-(S,S)-) configurations are assigned. X-Ray crystal structures are presented for the complexes [Co(sarmp)H₂O]ClO₄, [Co((S,S)-promp)H₂O]ClO₄, [Co(rac-bapap)H₂O]ClO₄ and endo-[Co(rac-malmp)H₂O]ClO₄. Ligand acid dissociation and Co^II and Fe^II complex-formation constants are reported.     

Synthesis of 2, 5, 5-Trimethylhepta-2, 6-Dien-4-One (Artemisia Ketone): II. Using A Thioacetal Monoxide

The polymer-bound catalyst 3a-e inserted some spacer ([-NHCO(CH_{2 10- n}; n = 0,1,2,3,4) connecting the catalytic moiety [cyclo(-(S)-Phe-(S)-His)], [(S,S)-1] and 2% cross-linked Merrifield's polymer, have been prepared and their catalytic efficiency for the enantioselective hydrocyanation of 3-phenoxybenzaldehyde was studied.     

Synthesis of 20<Emphasis Type="Italic">S</Emphasis>-protopanaxadiol <Emphasis Type="Italic">β</Emphasis>-D-galactopyranosides

20S-Protopanaxadiol (3β,12β,20S-trihydroxydammar-24-ene) 3-, 12-, and 20-O-β-D-galactopyranosides were synthesized for the first time. Condensation of 12β-acetoxy-3β,20S-dihydroxydammar-24-ene (1) and 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosylbromide (α-acetobromogalactose) (2) under Koenigs–Knorr conditions with subsequent removal of the protecting groups resulted in regio- and stereoselective formation of 20S-protopanaxadiol 3-O-β-D-galactopyranoside, an analog of the natural ginsenoside Rh₂. Glycosylation of 12β,20S-dihydroxydammar-24-en-3-one (5) by 2 with subsequent treatment of the reaction products with NaBH₄ in isopropanol and deacetylation with NaOMe gave 20S-protopanaxadiol 12- and 20-O-β-Dgalactopyranosides.     

乳酸类合成子构建的四连接螺旋手性配位聚合物的合成、结构和光催化性质

通过乳酸衍生物和3-溴-4-羟基苯甲酸的组合得到对映体3-溴-4-(((1R)-1-羧基乙基)氧基)苯甲酸(R-H₂bba)和3-溴-4-(((1S)-1-羧基乙基)氧基)苯甲酸(S-H₂bba)。以其为手性合成子在水热条件下分别与1,3-二(吡啶-4-基)丙烷(1,3-dpp)和Ni²⁺反应,构建了对映手性配位聚合物{[Ni(R-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n(HU12-R)和{[Ni(S-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n(HU12-S)。结构分析揭示HU12-R和HU12-S是具有dia网络特征的三维螺旋骨架。在骨架中,阴离子配体R-bba^2-和S-bba^2-分别与Ni²⁺中心连接在一起围绕2,螺旋轴得到一对小的对映螺...     

乳酸类合成子构建的四连接螺旋手性配位聚合物的合成、结构和光催化性质

通过乳酸衍生物和3-溴-4-羟基苯甲酸的组合得到对映体3-溴-4-(((1R)-1-羧基乙基)氧基)苯甲酸(R-H₂bba)和3-溴-4-(((1S)-1-羧基乙基)氧基)苯甲酸(S-H₂bba)。以其为手性合成子在水热条件下分别与1,3-二(吡啶-4-基)丙烷(1,3-dpp)和Ni²⁺反应,构建了对映手性配位聚合物{[Ni(R-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n (HU12-R)和{[Ni(S-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n (HU12-S)。结构分析揭示HU12-R和HU12-S是具有dia网络特征的三维螺旋骨架。在骨架中,阴离子配体R-bba^2-和S-bba^2-分别与Ni²⁺中心连接在一起围绕2₁螺旋轴得到一对小的对映螺旋链,而1,3-dpp与Ni²⁺中心则围绕4₁螺旋轴构建出另外一对大的对映螺旋链。电化学测试显示HU12-R属n型半导体,具有低阻抗性质,对紫外可见光有很强的吸收能力。进一步光催化实验证实在紫外光照射下所得配合物对染料降解有明显催化效果。     

Synthesis and Some Transformations of Derivatives of Pyrido[3,2-b]indole (δ-Carboline)

The reactions of 2-dimethyliminomethyl-3-(p-nitrophenyl)aminoindole chloride with compounds with an active methylene center have been studied. A series of derivatives of -carboline have been synthesized. By the reaction of 3-ethoxycarbonyl-2-methyl-1-p-nitrophenylpyrido[3,2-b]indolinium chloride with the diethyl acetal of DMF the corresponding 2-dimethylaminovinyl derivative was synthesized which was converted into 5-p-nitrophenyl-1-oxo-1,10-dihydropyrano[3',4':5,6]pyrido[3,2-b]indol-5-ium chloride in the presence of acid.     

Single-crystal-to-single-crystal Transformation of the Dichloromethane Solvate of the Shiff Base Manganese(III) Complex to a Solvent Free Material

The chloride complex of Mn(III)with an optically active Schiff base derived from3,5-tert-butyl-salicyl aldehyde and(1R,3S)-1,2,2,-trimethylcyclopentane-1,3-diaminecrystallizes as a 1 : 1 solvate (I) withCH₂Cl₂ and transforms at room temperature toa solvent-free compound (II) without destructionof the crystals. Two X-ray diffraction experimentscarried out on the same crystal at 120 K revealed thatthe guest CH₂Cl₂ molecules are completelyenclosed in the host matrix and that drasticconformational changes of the complex molecules occurduring removal of solvent. A possible mechanism of thecrystal transformation is disscused. The spectralevidence on association of the metal complex withdichloromethane in solution are demonstrated.     

Technetium(V) complexes of dithiocarbazate derivatives

The neutral complex [TcOCl(hdc)] (1) (hdc?=?S-methyl-β-N-(2-hydroxyphenylethylidene)dithiocarbazate) was prepared by reaction of (n-Bu₄N)[TcOCl₄] with an equimolar amount of H₂hdc in ethanol/dichloromethane at room temperature. With a fourfold mol excess of H₂hdc in methanol/acetone, the ‘3?+?2’ complex [TcO(hdc)(adc)] (2) (adc?=?S-methyl-β-N-(prop-2-ylidene)dithiocarbazate) was isolated. Adc was formed by ketone exchange between solvent acetone and the hydroxyacetophenone fragment of hdc. Compounds 1 and 2 were characterized by infrared spectroscopy, ¹H NMR spectrometry, elemental analysis and single-crystal X-ray crystallography. Complex 1 has square-pyramidal geometry with the SNO-donor atoms of the tridentate chelate hdc and chloride forming a square plane, with the oxo oxygen atom in the apical position. Complex 2 has a distorted octahedral geometry, with an S₂N₂ donor set in the equatorial plane and the oxo and phenolate oxygen atoms in trans apical positions.     

Enantioselective fluorescent recognition of mandelate by substituted BINOL in aqueous solutions

The fluorescent photo-induced electron transfer chemosensors (R)-1, (R)-2, (S)-1 and (S)-2 based on the 3,3′-positions of 1,1′-bi-2-naphthol were designed for their recognition of mandelate. The binding properties for mandelate were examined by the fluorescence spectra. The high fluorescence sensitivity and enantioselectivity make compound (R)-2 a practically useful sensor for the recognition of mandelate in CH₃OH/H₂O system (1:1, 0.01 M Tris–HCl buffer, pH 7.4).     

BiCl3-Catalyzed Diastereoselective Intramolecular [4+2] Cycloaddition Reactions Leading to Pyrazole Annulated New Sulfur Heterocycles

Abstract

Intramolecular [4+2] cycloaddition reactions of N-aryl imines generated in situ from anilines and the S-allyl derivatives of pyrazole aldehydes have been carried out in the presence of catalytic amounts of BiCl₃ to provide the corresponding hexahydropyrazolo [4′,3′:5,6]thiopyrano[4,3-b]quinolines in excellent yields. The reactions are highly diastereoselective and the only cis products are isolated exclusively.