Synthesis of pyrrole-dihydrothiazole ensembles from 1-allenyl-1H-pyrrole,isothiocyanates, and propargyl bromide

Russian Journal of Organic Chemistry - N-Alkylidene-1-(propargylsulfanyl)-2-(1H-pyrrol-1-yl)buta-1,3-dien-1-amines at treatment by a superbasic system t-BuONa–THF–DMSO under standard...     

Are electrocyclization reactions of (3Z)-1,3,5-hexatrienone and nitrogen derivatives pseudopericyclic? A DFT study

[reactions: see text] Electrocyclization reactions of (3Z)-1,3,5-hexatrienone and nitrogen derivatives were studied by performing density functional theory (DFT) calculations together with the 6-31+G* basis set. Reactants, products, and transition states for each reaction were localized and the IRC connecting reactants and products was also obtained. Magnetic properties were evaluated along the reaction path to elucidate the characteristics of the reactions studied. As obtained from the calculations, electrocyclization of (3Z)-1,3,5-hexatrienone is a pericyclic process, as indicated by a variety of indexes, such as Nucleus Independent Chemical Shift (NICS), anisotropy of the magnetic susceptibility, or anisotropy of the current-induced density (ACID). This reaction presents characteristics of pericyclic reactions despite the activation energy lowering relative to the electrocyclization of (4Z)-1,2,4,6-heptatetraene, and the relatively small NICS values observed in the transition state. Magnetic properties indicate that an enhancement of the aromaticity relative to reactants and products occurs revealing the absence of orbital disconnections on the cyclic loop of interacting orbitals. Only two reactions among those studied exhibit pseudopericyclic character due to the in-plane attack of the lone pair on nitrogen. In these cases, the reactions showed no barrier for the electrocyclization process, and no aromaticity enhancement was observed.     

A DFT study of the pericyclic/pseudopericyclic character of cycloaddition reactions of ethylene and formaldehyde to buta-1,3-dien-1-one and derivatives

Cycloaddition reactions of ethylene and formaldehyde to buta-1,3-dien-1-one and derivatives were studied by performing a density functional theory study with the 6-31+G* basis set. Reactants, products, and transition states for each reaction were localized, and the path connecting reactants and products was also obtained. Magnetic properties were evaluated along the reaction path to elucidate the characteristics of the reactions studied. Also, a natural bond orbital analysis was performed to study the orbital interactions in the transition states. Calculations indicate that all reactions are pericyclic except three cases, which are pseudopericyclic reactions. In the latter, transition states are almost planar, and magnetic properties do not reveal aromatization enhancement in their transition states. Also, though the participation of lone pairs diminish the pericyclic character of the reactions, sometimes this participation is not enough to generate a change to a pseudopericyclic path. Overall, magnetic properties reveal as a good criterion to elucidate the characteristics of the reactions studied, though a combined application of several criteria is recommended.     

Synthesis, characterization and fluorescence studies of novel bi-phenyl based acrylate and methacrylate

4-[(1E)-3-(biphenyl-4-yl)buta-1,3-dien-1-yl]phenyl prop-2-enoate (ACH) and 4-[(1E)-3-(biphenyl-4-yl)buta-1,3-dien-1-yl]phenyl 2-methylprop-2-enoate (MCH) was synthesized from biphenyl in three steps and their structures were confirmed by elemental analysis, IR, NMR (1H, 13C, DEPT135, 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC) spectroscopic techniques. In this present study, various physicochemical characteristics we demonstrate solubility, color, absorbance and fluorescence property of novel biphenyl based acrylate and methacrylate measured in different solvents like benzene, dichloromethane, tetrahydrofuran, acetonitrile, dimethylsulfoxide and ethanol.     

Synthesis of 2,4-diphenyl-1H-pyrrol-1-amine derivatives

The direction of the reaction of 4-bromo-1,3-diphenyl-2-buten-1-one (γ-bromodypnone) with hydrazines depends on the nature of the substituent they contain. Reaction with 1-methylhydrazinium hydrosulfate gives 1-methyl-3,5-diphenylpyridazin-1-ium bromide but carboxylic acid hydrazides give N-(2,4-diphenyl-1H-pyrrol-1-yl)carboxylic acid amides. γ-Bromodypnone and phenylhydrazine give both 1,3,5-triphenyl-1,4-dihydropyridazine and N,2,4-triphenyl-1H-pyrrol-1-amine (15%). 1-(2,4-Dinitrophenyl)hydrazine gives the 2,4-dinitrophenylhydrazone of (Z)-4-bromo-1,3-diphenyl-2-buten-1-one. Condensation of 2,4-diphenyl-1H-pyrrol-1-amine with aromatic aldehydes readily leads to N-(arylmethylidene)-2,4-diphenyl-1H-pyrrol-1-amines and alkylation with methyl iodide gives N,N-dimethyl-2,4-diphenyl-1H-pyrrol-1-amine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 404–414, March, 2009.     

Identity double-proton transfer in (3Z)-3-hydroxy-1,4-di(quinolin-2-yl)but-3-en-2-one

Although there is a very fast (on the NMR timescale) double-proton transfer in (1Z,3Z)-3-hydroxy-4-quinolin-2-yl-1-quinolin-2(1H)-ylidenbut-3-en-2-one (the product of the condensation of ethyl oxalate with 2lithiomethylquinoline), it is the only species present in chloroform solution. Comparison of the product of condensation of ethyl oxalate with 2lithiomethyl derivatives of pyridine (recent studies) and quinoline (present studies) shows that benzoannulation considerably affects the tautomeric equilibrium. The observed changes are not only quantitative but also qualitative. Moreover, contrary to the proton transfer in the pyridine tautomers, this process is fast in the quinoline tautomers. Comparison of the experimental and ab initio/DFT GIAO-calculated (13)C and (15)N chemical shifts for the transition states in the proton-transfer reactions between (1Z,3Z)- 3-hydroxy-4-quinolin-2-yl-1-quinolin-2(1H)-ylidenbut-3-en-2-one and its tautomers support the theory that a concerted identity reaction takes place between the enolimine-enaminone and enaminone-enolimine tautomeric forms. As a consequence, the most stable tautomeric form, (1Z,3Z)-1,4-di(quinolin-2-yl)buta-1,3-diene-2,3-diol, is not present in the tautomeric mixture.     

Synthesis and structure of 1-(buta-1,3-dien-2-yl)pyrazoles and their behavior in Diels-Alder reactions

A convenient procedure has been developed for the synthesis of cis-and trans-isomeric 1-(buta-1,3-dien-1-yl)-1H-pyrazoles by reaction of the corresponding pyrazoles with β-methylacrolein diethyl acetal and subsequent 1,4-cleavage of the nucleophilic substitution products. The behavior of the title compounds in Diels-Alder reactions with maleic anhydride has been studied. According to the ¹H NMR data, 1-(buta-1,3-dien-1-yl)-1H-pyrazole is a mixture of cis and trans isomers. Butadienylpyrazoles having methyl groups in the pyrazole ring do not react with maleic anhydride.     

An ab initio/RRKM study of product branching ratios in the photodissociation of buta-1,2- and -1,3-dienes and but-2-yne at 193 nm

Ab initio G2M(MP2)//B3LYP/6-311G** calculations have been performed to investigate the reaction mechanism of photodissociation of buta-1,2- and -1,3-dienes and but-2-yne after their internal conversion into the vibrationally hot ground electronic state. The detailed study of the potential-energy surface was followed by microcanonical RRKM calculations of energy-dependent rate constants for individual reaction steps (at 193 nm photoexcitation and under collision-free conditions) and by solution of kinetic equations aimed at predicting the product branching ratios. For buta-1,2-diene, the major dissociation channels are found to be the single Cbond;C bond cleavage to form the methyl and propargyl radicals and loss of hydrogen atoms from various positions to produce the but-2-yn-1-yl (p1), buta-1,2-dien-4-yl (p2), and but-1-yn-3-yl (p3) isomers of C(4)H(5). The calculated branching ratio of the CH(3) + C(3)H(3)/C(4)H(5) + H products, 87.9:5.9, is in a good agreement with the recent experimental value of 96:4 (ref. 21) taking into account that a significant amount of the C(4)H(5) product undergoes secondary dissociation to C(4)H(4) + H. The isomerization of buta-1,2-diene to buta-1,3-diene or but-2-yne appears to be slower than its one-step decomposition and plays only a minor role. On the other hand, the buta-1,3-diene-->buta-1,2-diene, buta-1,3-diene-->but-2-yne, and buta-1,3-diene-->cyclobutene rearrangements are significant in the dissociation of buta-1,3-diene, which is shown to be a more complex process. The major reaction products are still CH(3) + C(3)H(3), formed after the isomerization of buta-1,3-diene to buta-1,2-diene, but the contribution of the other radical channels, C(4)H(5) + H and C(2)H(3) + C(2)H(3), as well as two molecular channels, C(2)H(2) + C(2)H(4) and C(4)H(4) + H(2), significantly increases. The overall calculated C(4)H(5) + H/CH(3) + C(3)H(3)/C(2)H(3) + C(2)H(3)/C(4)H(4) + H(2)/C(2)H(2) + C(2)H(4) branching ratio is 24.0:49.6:4.6:6.1:15.2, which agrees with the experimental value of 20:50:8:2:2022 within 5 % margins. For but-2-yne, the one-step decomposition pathways, which include mostly H atom loss to produce p1 and, to a minor extent, molecular hydrogen elimination to yield methylethynylcarbene, play an approximately even role with that of the channels that involve the isomerization of but-2-yne to buta-1,2- or -1,3-dienes. p1 + H are the most important reaction products, with a branching ratio of 56.6 %, followed by CH(3) + C(3)H(3) (23.8 %). The overall C(4)H(5) + H/CH(3) + C(3)H(3)/C(2)H(3) + C(2)H(3)/C(4)H(4) + H(2)/C(2)H(2) + C(2)H(4) branching ratio is predicted as 62.0:23.8:2.5:5.7:5.6. Contrary to buta-1,2- and -1,3-dienes, photodissociation of but-2-yne is expected to produce more hydrogen atoms than methyl radicals. The isomerization mechanisms between various isomers of the C(4)H(6) molecule including buta-1,2- and -1,3-dienes, but-2-yne, 1-methylcyclopropene, dimethylvinylidene, and cyclobutene have been also characterized in detail.     

近红外菁染料敏化的准固态太阳电池的光电化学研究

一个新型的近红外五甲川菁染料敏化剂(Cy)通过3,3-二甲基-1-乙基-2-[4-(N-苯乙酰氨基]-1,3-丁二烯-1-基]-3H-苯并[e]吲哚碘盐和5-羧基-1-丁基-2,3,3-三甲基-3H-吲哚碘盐的Knoevenagel缩合反应合成, 其结构用核磁、质谱和紫外等方法进行了确定; 使用疏水性气相法纳米SiO2 R974固化1-丁基-3-丙基咪唑碘离子液体制备了一种新的准固态电解质, 将其应用于菁染料(Cy)敏化的太阳电池, 对该染料敏化的准固态太阳电池的光电化学性能进行了研究. 在AM1.5G标准光源下, 得到1.49%的光电转换效率. 此方法对拓展准固态染料敏化太阳电池的研究具有一定的意义.     

Transmetallation of beta-allenyl silanes: efficient synthesis of dienyl chlorostannanes and chlorostibines

The reaction of 1-trimethylsilylbuta-2,3-diene with tin tetrachloride, antimony trichloride or antimony pentachloride gave the corresponding buta-1,3-dien-2-yl halostannane or stibine derivatives; this ligand exchange was extended to other beta-allenylsilanes.     

DFT studies on tautomeric preferences of 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione in the gas phase and in solution

Density functional theory (DFT) calculations show that in vacuum such α-diketone as 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione is much less stable than its enolimine–enaminone ((1Z,3Z)-3-hydroxy-4-(pyridin-2-yl)-1-(quinolin-2(1H)-ylidene)but-3-en-2-one) and dienaminone tautomers ((1Z,3Z)-1-(pyridin-2-yl)-4-(quinolin-2-yl)buta-1,3-diene-2,3-diol). Other its tautomers (multiple basic and acidic centers in their molecules enable multiple proton transfer to take place) are even more labile. Strength of the intramolecular hydrogen bonds and aromatic character of the (quasi)rings [proved by the Harmonic Oscillator Model of Aromaticity (HOMA) index] in their molecules were found to be responsible for the observed tautomeric preferences. Polar and basic solvent disfavors and favors the enolimine and enaminone tautomers, respectively.     

Reactions of but-2-yne-1,4-diylbis(triphenylphosphonium) dihalides with SH- and NH-nucleophiles

But-2-yne-1,4-diylbis(triphenylphosphonium) diiodide reacts with 2-sulfanylethan-1-ol in the presence of triethylamine to form a 1 : 1 adduct. Under similar conditions, ethane-, butane- and 2-methylbutane- 1-thiols form [4-(alkylsulfanyl)buta-1,3-dien-1-yl]triphenylphosphonium iodides, probably via β-cleavage of the original salt involving vinylethynyl intermediate. Features of the reaction of but-2-ynebisphosphonium salt with 3,5-dimethylpyrazole, hydrazine and its derivatives have been studied.     

(1Z,3Z)-1,4-Di(pyridin-2-yl)buta-1,3-diene-2,3-diol: the planar highly conjugated symmetrical enediol with multiple intramolecular hydrogen bonds

1H, (13)C, and (15)N NMR spectral data show that in chloroform solution (1Z,3Z)-1,4-di(pyridin-2-yl)buta-1,3-diene-2,3-diol, OO, is in ca. 9:1 equilibrium with (3Z)-3-hydroxy-1,4-di(pyridin-2-yl)but-3-en-2-one, OK, while no 1,4-di(pyridin-2-yl)-2,3-butanedione, KK, was detected. The species present in the tautomeric mixture were identified by comparing their experimental chemical shifts with those known for similar compounds as well as with the theoretically calculated (GIAO-HF/DFT) values. Ab initio calculations show that OK and especially the highly conjugated OO forms are preferred in the tautomeric mixtures both in vacuo and in chloroform solution. Comparison of experimental (Arrhenius) and calculated (ab initio) energies of OK shows that the MP2/6-31G//RHF/6-31G method gives the most precise results. There are one and two strong O-H.N hydrogen bonds present in the molecules of the former and latter compound, respectively. Other tautomeric forms, e.g., dienaminedione [(1Z,4Z)-1,4-di[pyridin-2(1H)-ylidene]butane-2,3-dione], and their rotamers were found to have higher energies. The single-crystal X-ray diffraction studies show that dienediol OO is the only tautomeric form present in the crystal at 173 K. Its almost perfectly planar molecule is stabilized by two strong intramolecular O-H.N hydrogen bonds.     

Metal-assisted synthesis of enantiopure spirocyclic β-lactams from azetidine-2,3-diones

A novel approach to enantiopure spirocyclic β-lactams has been developed by using different intramolecular metal-catalyzed cyclization reactions in monocyclic unsaturated alcohols. The access to cyclization precursors, 2-azetidinone-tethered homoallylic alcohols, (buta-1,3-dien-2-yl)methanols, and α-allenols was achieved by regio and stereoselective addition of stabilized organo-indium reagents to azetidine-2,3-diones in aqueous environment.     

Five-Membered 2,3-dioxoheterocycles: XCV. Recyclization of 4-benzoyl-5-phenylfuran-2,3-dione at the action of substituted 1,3,3-trimethyl-2-azaspiro[4.5]dec-1-enes. Crystal and molecular structure of substituted 5-(2-azaspiro[4.5]dec-1-ylidene)cyclopent-3-ene-1,2-dione

4-Benzoyl-5-phenylfuran-2,3-dione reacts with 2′,5′,5′-trimethyl-4′,5′-dihydro-4H-spiro[naphthalene-1,3′-pyrrol]-4-one and 8-(2-methoxy-5-methylphenyl)-1,3,3,9-tetramethyl-2-azaspiro[4.5]deca-1,7-dien-6-one with the formation of (Z)-3-benzoyl-5-(5′,5′-dimethyl-4-oxo-4H-spiro[naphthalene-1,3′-pyrrolidin]-2′-ylidene)-4-phenylcyclopent-3-ene-1,2-dione, whose structure was proved by XRD analysis, and of (Z)-3-benzoyl-5-{8-(2-methoxy-5-methylphenyl)-3,3,9-trimethyl-6-oxo-2-azaspiro[4.5]dec-7-en-1-ylidene}-4-phenylcyclopent-3-ene-1,2-dione.     

Reaction of 2-aza-1,3,5-trienes with superbases: an unexpected approach towards exomethylene tetrahydroazepines

Russian Chemical Bulletin - Reaction of 2-methoxy-N-(1-methylpropylidene)-1-(methylsulfanyl)buta-1,3-dien-1-amine with ButOK resulted in...     

Magnetic properties and aromaticity of o-, m-, and p-benzyne

The relative aromaticities of the three singlet benzyne isomers, 1,2-, 1,3-, and 1,4-didehydrobenzenes have been evaluated with a series of aromaticity indicators, including magnetic susceptibility anisotropies and exaltations, nucleus-independent chemical shifts (NICS), and aromatic stabilization energies (all evaluated at the DFT level), as well as valence-bond Pauling resonance energies. Most of the criteria point to the o-benzyne相似文献   

Reaction of cytisine with alka-1,3- and -2,3-dien-2-ylphosphonates

Methods have been developed for functionalizing the alkaloid cytisine via introduction of alka-1,3- and -2,3-dien-2-ylphosphonate fragments. The main pathway of the reaction of cytisine with 2-(diethoxyphosphoryl) alka-2,3-dien-1-yl methanesulfonates is nucleophilic substitution of the methanesulfonyloxy group with retention of the alkadiene skeleton. A minor reaction pathway is nucleophilic substitution with formation of alka-1,3-dien-2-ylphosphonates. Cytisine conjugates with exclusively alka-1,3-dien-2-ylphosphonate fragment have been synthesized by copper(I)-catalyzed 1,3-dipolar cycloaddition of N-(prop-2-yn-1-yl)cytisine to 3-azidoalka-1,3-dien-2-ylphosphonates.     

Efficient entry to diversely functionalized spirocyclic oxindoles from isatins through carbonyl-addition/cyclization reaction sequences

A novel approach to diversely functionalized spirocyclic oxindoles has been developed by using different metal-mediated carbonyl-addition/cyclization reaction sequences. Spirocyclization precursors, 2-indolinone-tethered homoallylic alcohols, (buta-1,3-dien-2-yl)methanols, and alpha-allenols have been obtained by regioselective addition of stabilized organoindium reagents to isatins in aqueous environment. Ruthenium-, silver-, and palladium-catalyzed reactions of the above unsaturated alcohol derivatives provided oxaspiro oxindoles.     

Synthesis of Fluorine-Containing 2-Pyrrolyl- and 2-Indolyl-Substituted 1,3-Benzothiazin-4-ones

Russian Journal of Organic Chemistry - New 2-(1-methyl-1H-pyrrol-2-yl)- and 2-(1-methyl-1H-indol-3-yl)-5-fluoro- and -6,7,8-trifluoro-1,3-benzothiazin-4-ones have been synthesized in high yields by...