1,3-Dichloro-2-butene: a useful precursor for the 2-butene-1,3-dianion and its corresponding 1,3-dipolar synthon

The reaction of 1,3-dicloro-2-butene (1; 5:1 Z:E-mixture) with lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 1% molar) in the presence of different electrophiles [EtCHO, PrⁱCHO, Bu^tCHO, c-C₆H₁₁CHO, Me₂CO, Et₂CO, (CH₂)₄CO, (CH₂)₅CO, (c-C₃H₅)₂CO, Me₃SiCl] in THF at temperatures ranging between −78 and −50°C gives, after hydrolysis with water, the corresponding products 2 in different Z:E-ratios depending on the electrophile used. Treatment of some diols 2 with hydrochloric acid gives dienic alcohols 3 or substituted dihydropyrans 4, depending on the structure of the starting diol. Finally, the same dichlorinated starting material is transformed into the corresponding allylic amines derived from morpholine and benzyl methyl amine and submitted to the same DTBB-catalysed lithiation as above, so after reaction with different electrophiles [Bu^tCHO, c-C₆H₁₁CHO, Me₂CO, Et₂CO, (CH₂)₄CO, (CH₂)₅CO, Me₃SiCl] and final hydrolysis with water, compounds 7 are isolated having a Z-configuration. A mechanistic explanation for this behaviour is given.     

8-羟基喹啉衍生物对某些阴离子的双重光谱响应

本文以5-甲酰基-8-羟基喹啉(5M8Q)作为阴离子识别探针,通过紫外、荧光等光谱仪考察其对阴离子识别作用。实验显示:在乙腈溶液中5M8Q对F-、CH3COO-和H2PO4-等阴离子有灵敏的识别作用:F-、CH3COO-和H2PO4-可诱导5M8Q吸收光谱红移,吸收峰位置由322nm红移至400nm。当F-、CH3COO-和H2PO4-浓度为5M8Q两倍当量时,5M8Q荧光显著增强且分别增强至103、60和13倍。结果表明:5M8Q对F-、CH3COO-和H2PO4-有灵敏的双重光谱响应,并且表现出荧光增强型识别性质。     

A novel synthesis of amino-1,2-oxazinones as a versatile synthon for beta-amino acid derivatives

The radical addition-cyclisation of alpha, beta-unsaturated hydroxamates containing an oxime ether provides a novel method for the stereoselective synthesis of amino-1,2-oxazinones. Its synthetic utility is demonstrated by a stereoselective synthesis of beta-amino acid derivatives, such as alpha-alkyl-beta-amino-gamma-lactone and alpha,beta-disubstituted beta-lactam.     

A ferrocenyl-guanidine derivative as a highly selective electrochemical and colorimetric chemosensor molecule for acetate anions

A highly preorganized chemosensor molecule 1 based on a ferrocenyl-guanidine decorated with a chromogenic aryl azo moiety recognizes the acetate anion in acetonitrile solution. At first, receptor 1 underwent two-step oxidation events. Initially, oxidation of 1 occurs at the Fe(II) centre (E(p) = 440 mV) to form a ferrocenium species, followed by fast electron transfer from the guanidine moiety of the receptor to the Fe(III) centre with concomitant generation of an Fe(II) species with a radical cation centred at the nitrogen atom. In the second step, the radical cation species formed should undergo electrochemical oxidation at higher potential (E(p) = 830 mV). This assumption is supported by spectroelectrochemical studies. A remarkable cathodic shift (182 mV) of the ferrocene/ferrocenium oxidation peak (E(p) = 440 mV) and a progressive red-shift (Δλ = 30 nm) of the low energy band are observed in its absorption spectrum upon complexation of receptor 1 with the acetate anion. This change in the absorption spectrum is accompanied by a colour change from yellow to orange, which can be used for the "naked-eye" detection of this anion. Its monoprotonated form is able to selectively sense the less basic Cl(-), Br(-), NO(3)(-), and HSO(4)(-) anions: the oxidation redox peak at E(p) = 865 mV is cathodically shifted (107-182 mV).     

2-(2-Nitroethyl)-1,3-dioxolane as reagent for 3-oxopropyl anion synthon : a new route to jasmonoid and prostaglandin intermediates

2-(2-Nitroethyl)-l,3-dioxolane 18 a versatile reagent for 3-oxopropyl anion synthon. New methodology, based on nitro- aldol condensation, oxidation and direct or indirect denitration sequence is developed for the conversion of 2-(2-nitroethyl)-l,3 dioxolane into (Z)-l,4-dioxodec-7-ene, (Z)-2-(2-pentenyl)-2-cy clopenten-l-one, methyl 9,12-dioxododecanoate and methyl 7-(5- oxocyclopentenyl)heptanoate, which are popular Intermediates for syntheses of (Z)-jasmonolds and prostaglandins.     

2-Deuterio-1,3-benzodithiolium perchlorate: A useful synthon for the preparation of aldehydes-1-d

2-Deuterio-1,3-benzodithiolium perchlorate reacted with Grignard reagents to give 2-alkyl or 2-aryl-2-deuterio-1,3-benzodithioles, which in turn could be hydrolysed to corresponding aldehydes-1-d.     

A Lewis acid-catalyzed tandem reaction enabling 2-arylglycerol derivative as a versatile 1,3-biselectrophile for the synthesis of 4H-chromenes and 2-pyridinones

Acid-catalyzed tandem reactions were established by employing a novel class of 2-arylglycerol derivative,5-aryl-1,3-dioxan-5-ol, as versatile 1,3-biselectrophile. In the reactions, 5-aryl-1,3-dioxan-5-ol works like atropaldehydes or 2-aryl malondialdehydes, and can react with 2-naphthols and β-keto amides, allowing the synthesis of 4H-chromenes and 5-aryl-2-pyridinones. High yields, good functional group tolerance,broad substrate scope and simple reaction operation make this protocol attractive.     

Structural model of silica nanowire assembled from a highly stable (SiO2)8 unit

The ground-state structures of silica clusters (SiO2)n for n = 1-8 were studied by performing calculations at the B3LYP/6-311+G(d) level of density functional theory. The results indicate that the growth mode of a silica nanowire based on small silica clusters may change at different wire lengths. A linear chain might be assembled from the smallest clusters of rhombic two-membered ring (2MR) with n < or = 5, while the growth motif changes at n = 6 into a more compact form composed of three-membered-rings (3MRs). The 3MR-containing structures become energetically favorable configurations for even longer silica clusters. In particular, the closed molecular ring consisting of 3MRs at n = 8 (i.e., (SiO2)8) with a high symmetry shows extreme energetic stability and relatively high chemical reactivity and thus is considered to be an important building block to assemble into silica nanowires. The relative stability of so-assembled silica nanowires were evaluated and compared with the models of silica nanowires in the literature.     

Coordinating ability of the heterocycles 1,3-dithia-2-arsa- and stiba-cyclopentanes. Part III. Dithioacid and dithiocarbamate complexes containing a free functional group. Crystal structure of 2-pyrrolidonedithiocarbamate of 1,3-dithia-arsa-cyclopentane

Three 1,1-dithioacids containing an additional functional group, 2-pyrrolidone-1-carbodithioic acid, 2-hydroxycyclopentene-1-carbodithioic acid, and 2-pyrrolidone-1,3-bis(carbodithioic) acid, were reacted with the Group 15 heterocycles 2-chloro-1,3-dithia-2-arsa- and stiba-cyclopentanes (CIMS₂C₂H₄; M = As, Sb). The dithiocomplexes obtained were characterized by spectroscopic methods and elemental analyses. The X-ray structure determination of the 2-pyrrolidonedithiocarbamate of 1,3-dithia-arsacyclopentane shows a monodentate behavior of the dithiocarbamate entity and the absence of participation of the carbonyl oxygen in the coordination.     

Synthesis and reactions of a stable 1,2-diaryl-1,2-dibromodisilene: a precursor for substituted disilenes and a 1,2-diaryldisilyne

Synthesis and isolation of the stable diaryldibromodisilene, Bbt(Br)SiSi(Br)Bbt, has been accomplished for the first time. The dibromodisilene underwent substitution reactions with organometallic reagents on the low-coordinated silicon atom to afford the corresponding substituted disilenes. Furthermore, the reaction of 1 with t-BuLi afforded the corresponding 1,2-diaryldisilyne, BbtSi[triple bond]SiBbt, the characters of which were revealed by spectroscopic and crystallographic analyses.     

Coordination ability of the heterocycles 1,3-dithia-2-arsa- and -stiba-cyclopentanes towards sulfur containing ligands,part II. Diheterocyclic dithiocarbamate complexes. X-ray structure of the 4-morpholinecarbodithioate of 1,3-dithia-2-arsa-cyclopentane

Summary A series of diheterocyclic dithiocarbamate complexes of the typeRNCS₂ MS₂C₂H₄, whereR=pyrrolidyl, 3-pyrrolyl, 4-morpholyl, 3-methlpiperidyl andM=As or Sb were obtained and characterized by IR,¹H, and¹³C-NMR, mass spectroscopy and elemental analyses. The X-ray crystal structure determination of the 4-morpholinecarbodithioate of 1,3-dithia-2-arsa-cyclopentane shows a monodentate behaviour of theRNCS₂ entity.Dedicated to Dr. Lydia Rodríguez on the Occasion of her 60th Birthday.     

2-Lithiated-2-phenyloxetane: a new attractive synthon for the preparation of oxetane derivatives

A valuable and direct method to access 2-substituted-2-phenyloxetanes by electrophilic quenching of the corresponding 2-lithiated derivative has, for the first time, been described. 2-Lithiated-2-phenyloxetane was found to be configurationally unstable. Evidence is presented to show that electron-transfer processes are also operative in the coupling reactions with electrophiles.     

1-Oxo-2-hydroxy-1,2-dihydroacronycine: a useful synthon in the acronycine series for the introduction of amino substituents at 6-position and for the conversion into isopropylfuroacridones

Thermic aromatic nucleophilic displacement of the methoxy group at C-6 of (+/-)-1-oxo-2-hydroxy-1,2-dihydroacronycine (2) by an amine is a reaction that gives a facile entry to acronycine derivatives bearing an amino substituent at this position. The introduction of the amino substituents was confirmed with a long-range 1H-15N correlation NMR spectrum at natural abundance. Under basic conditions, compound 2 can also be rearranged to the corresponding isopropylfuroacridone 12, in 80% yield.     

4,4-Bis(methylthio)azetidin-2-ones as synthons of 1,2- and 1,3-dicarbonyl systems

The importance of β-lactams as synthetic building blocks has been widely recognized in organic synthesis due to possible ring cleavage at any of the four single bonds of the β-lactam ring. We now report reactions involving breaking of the N1-C4 bond in differently substituted at C3 4,4-bis(methylthio)azetidin-2-ones, leading to formation of 1,2- and 1,3-dicarbonyl systems.     

Addition of 1,2- and 1,3-Dithiols to 2-alkoxypropenals - a New Method for the Production of Substituted Dithiacycloalkanes

The reaction of 2-alkoxypropenals with ethane-1,2-dithiols and propane-1,3-dithiols under various conditions was studied by ¹H NMR and chromato-mass spectrometry. Under kinetically controlled conditions at 20° in the absence of catalysts the addition of dithiols takes place according to the Markovnikov rule. The primary adducts are unstable and are quickly converted into the corresponding substituted 1,4-dithiacycloheptane or 1,4-dithiane. The latter in turn can be converted under the reaction conditions or at high temperature into a thiolane derivative. The reaction of 2-ethoxypropenal with a twofold excess of ethane-1,2-dithiol at 60°C in the presence of p-toluenesulfonic acid leads to 2-methyl-2,2'-bi(dithiolane)     

Theoretical study of the isomers of the anions N2 −, P3 −, N2P−, and NP2 −

It has been shown by nonempirical calculations of the potential surfaces of the isomers that for the anions N₃ ^– and N₂P^– linear structures are somewhat more favorable than others. For P₃ ^– and P₂N^– there are several isomers lying close together: linear, angular, and cyclic. The stability of the cyclic relative to the linear isomers increases sharply when two or all of the atoms of the 2nd period are replaced by their analogs in the subgroups of the 3rd or later periods.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1590–1597, July, 1990.     

New method for the synthesis and the mechanism of formation of 1,2-di-and 1,2,3-trialkyldiaziridines

A new simple approach to the synthesis of 1,2-di-and 1,2,3-trialkyldiaziridines has been developed based on direct chlorination of a mixture of the corresponding aldehyde and an excess of primary aliphatic amine in water. The mechanism of this reaction is proposed and confirmed by quantum chemical calculations at the density functional theory level. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1978–1982, November, 2006.     

Synthesis of a hexahydropyrimido[1,2-a]azepine-2-carboxamide derivative useful as an HIV integrase inhibitor

The hexahydropyrimido[1,2-a]azepine-2-carboxamide derivative 1 could be obtained by three synthetic strategies, which allowed access to multigram amounts of material of high purity and ee. Two strategies involved alternative approaches to the bicyclic pyrimidone core, with the most efficient one being a two-step sequence from commercially available starting materials exploiting a little precedented cyclisation reaction. The remaining steps to 1 included an efficient crystallisation of an intermediate as a single stereoisomer. An alternative strategy employing a chiral starting material led to products of low optical purity but allowed the assignment of the configuration of the stereogenic centre of 1.