Synthesis of some derivatives of 3-amino-3-desoxyerythrose and 3-amino-3-desoxy-D-3-erythrose

The synthesis of derivatives of 3-amino-3-deoxy-L-erythrose by LAH or LAD reduction of the oxime of 1,2-O-isopropylidene α-L -glycero-tetros-3-ulofuranose is described.     

1H and13C NMR spectra of 3-methyl-3-cyanocyclopropene and 3-phenyl-3-methylcyclopropene

Conclusions The¹H and¹³C NMR spectral parameters were found for 3-methyl-3-cyanocyclopropene and 3-phenyl-3-phenyl-3-methylcyclopropene. The proton-carbon coupling constants indicate the acetylenic nature of bonding in the cyclopropene ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1405–1408, June, 1985.     

Syntheses and Crystal Structures of the Novel Ternary Thioborates Na3BS3, K3BS3, and Rb3BS3

The orthothioborates Na₃BS₃, K₃BS₃ and Rb₃BS₃ were prepared from the metal sulfides, amorphous boron and sulfur in solid state reactions at temperatures between 923 and 973 K. In a systematic study on the structural cation influence on this type of ternary compounds, the crystal structures were determined by single crystal X‐ray diffraction experiments. Na₃BS₃ crystallizes in the monoclinic space group C2/c (No. 15) with a = 11.853(14) Å, b = 6.664(10) Å, c = 8.406(10) Å, β = 118.18(2)° and Z = 4. K₃BS₃ and Rb₃BS₃ are monoclinic, space group P2₁/c (No. 14) with a = 10.061(3) Å, b = 6.210(2) Å, c = 12.538(3) Å, β = 112.97(2) and a = 10.215(3) Å, b = 6.407(1) Å, c = 13.069(6) Å, β = 103.64(5)°, Z = 4. The potassium and rubidium compounds are not isotypic. All three compounds contain isolated [BS₃]^3– anions with boron in a trigonal‐planar coordination. The sodium cations in Na₃BS₃ are located between layers of orthothioborate anions, in the case of K₃BS₃ and Rb₃BS₃ stacks of [BS₃]^3– entities are connected via the corresponding cations. X‐ray powder patterns were measured and compared to calculated ones obtained from single crystal X‐ray structure determinations.     

3-cyclobutyl-3-ferrocenylcyclopropene and 3-cyclobutylidene-3-ferrocenylpropyne Synthesis and chemical properties

3-Cyclobutyl-3-ferrocenylcyclopropene was synthesized by the reactions of mono- or dibromoferrocenylcyclopropanes with Bu^tOK in DMSO. Treatment of dibromoferro-cenylcyclopropane with Bu^tOK in THF afforded 3-cyclobutylidene-3-ferrocenylpropyne in 52% yield. Heterolysis of the C-C bond in the three-membered ring of 3-cyclobutyl-3-ferrocenylcyclopropene at low and high temperatures was studied. Hydrolysis yielded 3-cyclobutyl-1H-cyclopentaferrocene and products with linear structures,viz., 3-cyclobutylidene-3-ferrocenylpropene,E- andZ-I-ferrocenyl-1-cyclobutylpropenes, and 1-cyclobutylidene-1-ferrocenylacetone. Cyclopropene reacts with 1,3-diphenylisobenzofuran to form two Diels-Alder adducts, while the enyne does not react with 1,3-diphenylbenzofuran. Facultad de Quimica, Universidad Nacional Autónoma de México, Cd. Universitaria, C.P. 04510, México D. F., México. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2177–2181, November, 1999.     

Total synthesis of stevastelins B3 and C3: structure confirmation of stevastelin B3 and revision of stevastelin C3

The total synthesis of stevastelin B3, stevastelin C3 and 5-deoxy derivative of stevastelin C3, novel 13-membered cyclic depsipeptides, is described. This study unambiguously confirmed the proposed absolute structure of stevastelin B3, and revealed that the structure of stevastelin C3 is incorrect. The correct structure of stevastelin C3 was established by the total synthesis to be 5-deoxy derivative of the proposed structure.     

Synthesis and Dehydrobromination of 3-Bromomethyl- and 3-Bromo-3-methoxymethylcyclobutane-1-carbonitriles and Methyl 3-Bromomethyl- and 3-Bromo-3-methoxymethylcyclobutane-1-carboxylates

The anti-Markownikoff products of bromination and bromomethoxylation of 3-methylenecyclobutane-1-carbonitrile and methyl 3-methylenecyclobutane-1-carboxylate were subjected to dehydrobromination by the action of potassium tert-butoxide in THF. The reaction takes two elimination pathways: 1,3-dehydrobromination to give bicyclobutane derivatives and 1,2-dehydrobromination leading to substituted methylenecyclobutane. Structural factors in the substrate were revealed, which are responsible for the ratio of the two concurrent elimination processes.     

Syntheses and Crystal Structures of BaAgTbS3, BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and CsAgUTe3

Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS₃, BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and CsAgUTe₃, were synthesized by the reactions of the elements at 1173–1273 K. For CsAgUTe₃ CsCl flux was used. Their crystal structures were determined by single‐crystal X‐ray diffraction studies. The sulfide BaAgTbS₃ crystallizes in the BaAgErS₃ structure type in the monoclinic space group C³,_2h‐C2/m, whereas the tellurides BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and CsAgUTe₃ crystallize in the KCuZrS₃ structure type in the orthorhombic space group D¹_,2⁷_,h‐Cmcm. The BaAgTbS₃ structure consists of edge‐sharing [TbS₆^9–] octahedra and [AgS₅^9–] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features ²_∞[MLnTe₃^2–] layers for BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and ²_∞[AgUTe₃^1–] layers for CsAgUTe₃. These layers comprise [MTe₄] tetrahedra and [LnTe₆] or [UTe₆] octahedra. Ba or Cs atoms separate these layers. As there are no short Q ··· Q (Q = S or Te) interactions these compounds achieve charge balance as Ba²⁺M⁺Ln³⁺(Q^2–)₃ (Q = S and Te) and Cs⁺Ag⁺U⁴⁺(Te^2–)₃.     

An improved synthesis of 3-deazaeytosine, 3-deazauracil, 3-deazacytidine,and 3-deazauridine

3-Dcazacytosine (4-amino-2-pyridone, 3 ), 3-doazauracil (4-hydroxy-2-pyridone, 5 ), 3-deaza-cytidine (4-amino-1-β-D-ribofuranosyl-2-pyridonc, 9 ), and 3-deazauridine (4-hydroxy-1-β-D-ribo-furanosyl-2-pyridone, 11 ) were prepared in high overall yields from 1-methoxy-1-buten-3-yne ( 1 ). Ethyl 3,5,5-triethoxy-3-pentenoate ( 2 ), obtained from acylatioti of 1 with diethyl carbonate and subsequent in situ conjugate addition of ethoxide, was cyelized with ammonia to provide 3 . Diazotization of 3 and subsequent in situ hydroxydediazotization afforded 5 . Nucleoside 9 was obtained from the stannic chloride-catalyzed condensation of bis-trimethylsilylated 3 and 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 7 ), followed by ammonolysis of the blocking groups. Diazotization of 9 and subsequent in situ hydroxydediazotization afforded nucleosidc 11 .     

Preparation of 3-Oxo- and 3-Ethylideneazetidine Derivatives

The preparation of 3-azetidinones with different N-substituents and their transformation to 3-ethylideneazetidines has been studied in relation with a projected synthesis of 3-ethylideneazetidine-2-carboxylic acid (= polyoximic acid; 1 ). The stable crystalline 3-azetidinone hydrochloride ( 18 ), obtained by hydrogenolysis of the known 1-(diphenylmethyl)-3-azetidenone ( 4 ), is described for the first time, From this key intermediate, 3-oxoazetidine-derived amides, exemplified by benzamide 12 ,urethanes (e.g. 17 ), and ureas (e.g. 20 ) can be prepared in good yield (Scheme 3). The olefination of 3-azetidinones with alkylidene(triphenyl)phosphoranes is a perparatively useful process only for derivatives with a pyramidal N-atom, e.g. the diphenylmethyl derivative 4 , and not for the amide 12 or the urethane 17 (Scheme 4). 3-Alkylidene-azetidines with an amide N-atom should, therefore, be prepared by exchange of the N-substituent after the introduction of the double bond.     

Synthesis of 3-epistrophanthidin and 3-epistrophanthidol

Chemistry of Natural Compounds - 3-Epistrophanthidin and 3-epistrophanthidol have been synthesized from strophanthidin and strophanthidol with yields of 10 and 40%, respectively. The substances...     

Non-Isothermal Kinetics of the Decomposition Reaction of Cluster [Ag3WS3Br]（PPh3）3 and [Cu3WS3Br]（PPh3）3

The thermal behaviors of clusters [Ag3WS3Br](PPh3)3 and [Cu3WS3Br](PPh3)3 (PPh3=triphenyl phosphine) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC and EDS techniques. The results showed that the evolution of PPh3 generally proceeded before the release of the other moiety in one or two step-mode. The mechanisms, the kinetic and the thermodynamic parameters for decomposition of PPh3 of both clusters were determined and calculated by jointly using several methods, which showed that its evolution was controlled by Avrami-Erofeev equation. The results also showed that there was no new stable phase composed of W-Ag(Cu)-S-Br after release of organic moiety PPh3 and that CVD method was not applicable to their further processing.     

Synthesis and characterization of the phosphorus triazides OP(N3)3 and SP(N3)3

Two explosive triazides of phosphorus(V), OP(N(3))(3) and SP(N(3))(3), have been prepared as neat substances and structurally characterized. Both compounds can be handled in gas, liquid, and solid states in submillimolar quantities. The melting points of OP(N(3))(3) and SP(N(3))(3) are +22 and -30 °C, respectively. The two triazides have been characterized by IR (Ar matrix and gas phase) and Raman (solid) spectroscopies. Their single-crystal structures were obtained by X-ray diffraction and found to be significantly distorted from the predicted ideal C(3) symmetry because of intermolecular interactions. The spectroscopic and structural properties are discussed in combination with density functional theory calculations.     

Nonadiabatic coupling in the 3 3Pi and 4 3Pi states of NaK

The excited 3 (3)Pi and 4 (3)Pi electronic states of the NaK molecule exhibit an avoided crossing, leading to the anomalous behavior of many features of the rovibrational energy levels belonging to each state. A joint experimental and theoretical investigation of these states has been carried out. Experimental measurements of the vibrational, rotational, and hyperfine structure of numerous levels of the 3 (3)Pi state were recently obtained using the Doppler-free, perturbation-facilitated optical-optical double resonance technique. Additional measurements for the 4 (3)Pi state as well as bound-free emission spectra from selected 3 (3)Pi, 4 (3)Pi, and mixed 3 (3)Pi to approximately 4 (3)Pi rovibrational levels are reported here. A model is also presented for calculating the mixed rovibrational level energies of the coupled 3 (3)Pi-4 (3)Pi system, starting from a 2x2 diabatic electronic Hamiltonian. The 3 (3)Pi and 4 (3)Pi potential curves and the coupling between them are simultaneously adjusted to fit the observed rovibrational levels of both states. The energy levels of the potential curves determined by the fit are in excellent agreement with experiment. The nonadiabatic coupling is sufficiently strong to cause an overall shift of 2-3 cm(-1) for many rovibrational levels as well as somewhat larger shifts for certain pairs of 3 (3)Pi to approximately 4 (3)Pi levels that would otherwise be very close together.     

Understanding the rate of spin-forbidden thermolysis of HN3 and CH3N3

The pyrolysis of the simplest azides HN(3) and CH(3)N(3) has been studied computationally. Nitrogen extrusion leads to the production of NH or CH(3)N. The azides have singlet ground states but the nitrenes CH(3)N and NH have triplet ground states. The competition between spin-allowed decomposition to the excited state singlet nitrenes and the spin-forbidden N(2) loss is explored using accurate electronic structure methods (CASSCF/cc-pVTZ and MR-AQCC/cc-pVTZ) as well as statistical rate theories. Nonadiabatic rate theories are used for the dissociation leading to the triplet nitrenes. For HN(3), (3)NH formation is predicted to dominate at low energy, and the calculated rate constant agrees very well with energy-resolved experimental measurements. Under thermal conditions, however, the singlet and triplet pathways are predicted to occur competitively, with the spin-allowed product increasingly favored at higher temperatures. For CH(3)N(3) thermolysis, spin-allowed dissociation to form (1)CH(3)N should largely dominate at all temperatures, with spin-forbidden formation of (3)CH(3)N almost negligible. Singlet methyl nitrene is very unstable and should rearrange to CH(2)NH immediately upon formation, and the latter species may lose H(2) competitively with vibrational cooling, depending on temperature and pressure.     

KMgF3:Ce3+,Tb3+纳米粒子中Ce3+→Tb3+的发光及能量传递

利用微乳液方法,合成了铈、铽共掺杂的氟镁钾纳米粒子,研究了体系中Ce3+→Tb3+的发光特性以及它们之间的相互作用,结果表明KMgF3:Ce3+Tb3+纳米粒子中存在Ce3+→Tb3+的能量传递过程,即Ce3+可以将吸收的能量直接传递给Tb3+离子,使得Tb3+的绿色发光强度大为增加.     

Mechanochemical synthesis and crystal structure of alpha'-AlD3 and alpha-AlD3

AlD3 AlD3 was synthesized by ball milling of 3LiAlD4 + AlCl3. Planetary ball milling at room temperature resulted in a mixture of AlD3 (alpha and alpha') and Al in addition to LiCl, whereas cryomilling at 77 K resulted in only AlD3 and LiCl. The AlD3 obtained was a mixture of about 2/3alpha and 1/3alpha'. Alpha' was determined by powder neutron diffraction to take the beta-AlF3 structure with space group Cmcm and a = 6.470(3), b = 11.117(5), and c = 6.562(2) A. It is built up of corner-sharing AlD6 octahedra in an open structure with hexagonal holes of radius 3.9 A. Alpha' slowly decomposes during storage at 40 degrees C. Alpha-AlD3 is also described by a corner-sharing AlD6 network but in a more dense ReO3-type arrangement. Both AlD3 modifications have slightly shorter Al-D distances compared to Na3AlD6, Na2LiAlD6, and K2NaAlH6.     

Pros and cons of σ -aromaticity

A discussion of σ-aromaticity requires a distinction between σ-conjugation, σ-electron delocalization, and σ-bond delocalization, all of which can be considered as prerequisites of σ-aromatic character. All molecules with three or more atoms encounter σ-conjugative interactions. Also, all σ-electrons are delocalized if the term delocalization is taken in its quantum theoretical meaning. However, σ-conjugation and σ-electron delocalization do not necessarily imply σ-bond delocalization. - One can distinguish between three different modes of σ-delocalization: ribbon delocalization in acyclic molecules and larger rings, surface delocalization in small rings, and volume delocalization in cage compounds. Surface delocalization of σ-electrons is found to lead to σ-bond delocalization. An example is cyclopropane. Bonding in cyclopropane can only be described in terms of nonclassical 2-electron 3-center and 4-electron 3-center bonds. Application of the criteria used to define π-aromaticity reveals that the properties of cyclopropane are in line with these criteria and that the term σ-aromaticity cannot be rejected on the grounds that aromaticity is restricted to π-electrons. The pros and cons of using the term σ-aromaticity in chemical discussions are presented.     

Chemoenzymatic syntheses of iGb3 and Gb3

[STRUCTURE: SEE TEXT] Efficient chemoenzymatic syntheses of iGb3 and Gb3 have been developed. Isoglobotrihexose and globotrihexose were enzymatically synthesized by a three-enzyme system in both solid and solution phases. Then iGb3 and Gb3 were chemically synthesized by coupling of the corresponding trisaccharides with lipid.     

Condensation of 5-bromo-, 3-bromo-, and 3-iodoacenaphthenequinones with 3-hydroxythionaphthene and its derivatives

The oxidation of 3-bromo-and 3-iodoacenaphthene has given 3-bromo-and 3-iodoacenaphthenequinones. The condensation of 5-bromo-, 3-bromo-, and 3-iodoacenaphthenequinones with 3-hydroxythionaphthene and its derivatives has yielded indigoid dyes, and the main light absorption maxima of these dyes have been determined.     

Condensation of 5-bromo-, 3-bromo-, and 3-iodoacenaphthenequinones with 3-hydroxythionaphthene and its derivatives

The oxidation of 3-bromo-and 3-iodoacenaphthene has given 3-bromo-and 3-iodoacenaphthenequinones. The condensation of 5-bromo-, 3-bromo-, and 3-iodoacenaphthenequinones with 3-hydroxythionaphthene and its derivatives has yielded indigoid dyes, and the main light absorption maxima of these dyes have been determined.