Construction of push—pull systems using β-formyl-β-nitroenamine

The review is focused on the application of β-formyl-β-nitroenamines, one of the push—pull alkenes, having the biased electron density as well as an electrophilic formyl group and a nucleophilic amino group in the organic synthesis. Due to the multi-functionality, β-formyl-β-nitroenamines exhibit versatile reactivity to facilitate the synthesis of polyfunctionalized compounds possessing push—pull property. Nitroenamines serve as a synthetic equivalent of unstable nitromalonaldehyde to afford nitropyrazoles, nitropyrimidines, nitrodiazepines, and nitrophenoles upon treatment with dinucleophiles such as hydrazines, amidines, 1,2-diamines, and ketones, respectively. When active methylene compounds allowed reacting with the nitroenamines, polyfunctionalized pyridones and 2-amino-5-nitropyridines are obtained. In addition, nitroenamines undergo [4+2] self-condensation to afford 3,5-dinitropyridinium ion, which is easily trapped by benzene derivatives leading to 4-arylated 1,4-dihydropyridines.     

One-pot reactions of nitroenamines with anilines and ethyl glyoxylate

In a simple, one-pot, catalyst-free procedure starting from heterocyclic nitroenamines, substituted anilines and ethyl glyoxylate new ethyl 2-arylamino-3-nitro-propionates were prepared in good to excellent yields. Depending on the substituent pattern of the anilines applied, two routes for the one-pot reaction are suggested. Additionally, it was demonstrated that these multifunctional compounds of aza-Morita–Baylis–Hillman type were also formed in two-step protocols either from imines and nitroenamines or from the adducts of nitroenamines and ethyl glyoxylate with anilines.     

Synthesis of Trisubstituted Isoxazoles from Nitroenamines and Aromatic Aldehydes

A novel approach for the synthesis of trisubstituted isoxazoles from nitroenamines and aromatic aldehydes is developed. L ‐Proline/potassium carbonate system was employed to promote this process. The reaction underwent nucleophilic attack of nitroenamines to aromatic aldehydes, intramolecular denitration, tautomerization and elimination of H₂O to furnish the target compounds.     

Investigation by dynamic NMR spectroscopy of the mechanism of rotation about the carbon?double bond in nitroenamines

Rapid Z,E-isomerization of nitroenamines R? NH? CH?C(NO₂)COOCH₃ in solutions was investigated by dynamic NMR spectroscopy. In weakly basic solvents all the studied nitroenamines isomerize by a thermal mechanism. In pyridine the isomerization proceeds by the thermal mechanism in aliphatic enamines with R?? CH₃, ? COCH₃ and H, but involves the formation of an intermediate mesomeric ion with kinetically controlled ionization of the N? H bond in the case of aromatic nitroenamines where R = X—Ph-.     

Hindered rotation around C-N bond in nitroenamines

Conclusions The relation between the value of the rotation barrier around the C-N bond of nitroenamines and the type of solvent is determined mainly by the solvation of the nitroenamine molecule in the ground state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2392–2395, October, 1978.     

Reaction of Naphtho- and Benzimidazolequinones with Enamines. Synthesis of Condensed Benzofurans and Indoles

The reaction of naphthoquinone with nitroenamines and the interaction of benzimidazolequinones with derivatives of -aminocrotonic ester have been studied. It was shown that in the first case only the synthesis of naphthofurans occurs but in the second imidazoindoles are formed.     

Recent advances in azaborine chemistry

The chemistry of organoboron compounds has been primarily dominated by their use as powerful reagents in synthetic organic chemistry. Recently, the incorporation of boron as part of a functional target structure has emerged as a useful way to generate diversity in organic compounds. A commonly applied strategy is the replacement of a CC unit with its isoelectronic BN unit. In particular, the BN/CC isosterism of the ubiquitous arene motif has undergone a renaissance in the past decade. The parent molecule of the 1,2-dihydro-1,2-azaborine family has now been isolated. New mono- and polycyclic B,N heterocycles have been synthesized for potential use in biomedical and materials science applications. This review is a tribute to Dewar's first synthesis of a monocyclic 1,2-dihydro-1,2-azaborine 50 years ago and discusses recent advances in the synthesis and characterization of heterocycles that contain carbon, boron, and nitrogen.     

The Chemistry of Vicinal Diamines

Especially in the field of enantioselective synthesis , vicinal diamines (1,2-diamines) 1 and compounds easily prepared from them—such as 1,2-bisimines, 1,2-diamides, or imidazolidin-2-ones—are widely used by organic chemists. Various strategies have been developed to produce these compounds selectively. Many natural products and medicinal agents also contain a 1,2-diamino unit.     

The Reaction of Cyclic Nitroenamines with Isocyanates. Synthesis of 1,6-Polymethylene-6-nitromethyl-1,3,5-triazine-2,4-dione Derivatives

Summary. The reactions of cyclic nitroenamines with isocyanates were investigated. It was found that two different products could be obtained: in inert media -carbamoyl products were observed and when a strong base was used 1,6-polymethylene-6-nitromethyl-1,3,5-triazine-2,4-dione derivatives were isolated.     

The Reaction of Cyclic Nitroenamines with Isocyanates. Synthesis of 1,6-Polymethylene-6-nitromethyl-1,3,5-triazine-2,4-dione Derivatives

The reactions of cyclic nitroenamines with isocyanates were investigated. It was found that two different products could be obtained: in inert media -carbamoyl products were observed and when a strong base was used 1,6-polymethylene-6-nitromethyl-1,3,5-triazine-2,4-dione derivatives were isolated.     

Fluorescent property of 3-hydroxymethyl imidazo[1,2-a]pyridine and pyrimidine derivatives

ABSTRACT: BACKGROUND: Imidazo[1,2-a]pyridines and pyrimidines are important organic fluorophores which have been investigated as biomarkers and photochemical sensors. The effect on the luminescent property by substituents in the heterocycle and phenyl rings, have been studied as well. In this investigation, series of 3-hydroxymethyl imidazo[1,2-a]pyridines and pyrimidines were synthesized and evaluated in relation to fluorescence emission, based upon the hypothesis that the hydroxymethyl group may act as an enhancer of fluorescence intensity. RESULTS: Compounds of both series emitted light in organic solvents dilutions as well as in acidic and alkaline media. Quantitative fluorescence spectroscopy determined that both fused heterocycles fluoresced more intensely than the parent unsubstituted imidazo[1,2-a]azine fluorophore. In particular, 3-hydroxymethyl imidazo[1,2-a]pyridines fluoresced more intensely than 3-hydroxymethyl imidazo[1,2-a]pyrimidines, the latter emitting blue light at longer wavelengths, whereas the former emitted purple light. CONCLUSION: It was concluded that in most cases the hydroxymethyl moiety did act as an enhancer of the fluorescence intensity, however, a comparison made with the fluorescence emitted by 2-aryl imidazo[1,2-a]azines revealed that in some cases the hydroxymethyl substituent decreased the fluorescence intensity.     

Chemistry of 1,2-diphospholide anions and 1,2-diphospholes

The main trends in the chemistry of 1,2-diphosphacyclopentadienes (1,2-diphospholes) and their derivatives 1,2-diphosphacyclopentadienide anions (1,2-diphospholide anions) were systematized, analyzed, and generalized. Methods for the generation of 1,2-diphospholide anions and their reactions with organic and organoelement electrophiles, as well as with transition metal complexes, were considered. Particular attention was paid to the cycloaddition reactions of 1-alkyl-1,2-diphospholes to obtain polycyclic chiral phosphines. A comparative analysis of the reactivity of 1,2-diphospholes and 1,2-diphospholide anions with respect to other representatives of phosphacyclopentadienes and phosphacyclopentadienide anions was carried out. The potential of application of 1,2-diphosphacyclopentadiene derivatives for the design of materials with magnetic, catalytic, and optical properties was shown.

     

Reactions of 2-Arylthio- and 2-Arylsulfonyl-1-nitro-1-phenylethenes with Amines

2-Arylthio- and 2-arylsulfonyl-1-nitro-1-phenylethenes react with amines to give the corresponding nitroenamines whose configuration (E or Z) depends on the amine structure. Primary amines gives rise to Z-nitroenamines, secondary cyclic amines with 2-arylthio-1-nitroalkenes form E-nitroenamines, and with more reactive 2-arylsulfonyl-1-nitroalkenes E/Z-isomeric mixtures are obtained.     

有机硅骨架修饰的磷酸铝分子筛VPI-5的合成

分别以1,2-双(三乙氧基硅基)乙烷(BTESE)、1,2-双(三乙氧基硅基)乙烯(BTESEE)和苯基三乙氧基硅烷(PTES)为硅源, 通过一步法直接合成有机硅骨架修饰的磷酸铝分子筛VPI-5. 系统考察了各反应参数对产物结构与性质的影响, 并对产物的结构进行了表征. 表征结果表明, 有机基团通过硅原子被引入到分子筛骨架中. 有机基团的引入增加了分子筛的亲油性, 并且不同的有机基团对分子筛的亲油性的提高程度不同.     

Conformational and vibrational analysis with the aid of normal coordinate calculations

Many organic compounds exist as equilibrium mixtures of two or more molecular conformations, and vibrational spectroscopy can be used to obtain information about the structure of those conformations. Normal coordinate calculations are often an aid to those conformational studies and to making vibrational assignments for the different conformers. However, sometimes those calculations are partially inconclusive, and a few results are briefly discussed in which both conclusive and inconclusive results were obtained from calculations. Calculations are then applied to some 1,2-dichloro- and 1,2-dibromo-alkanes. Previous calculations on 1,2-dichloropropane and 1,2-dichlorobutane are revised, and calculations are reported for 1,2-dibromopropane, 1,2-dibromopropane-d₆, and 1,2-dibromobutane. Spectra are given for the last two of these compounds. A modified valence force field was determined for each family of 1,2-dihaloalkane that should be transferable to other members of the family.     

Electroreduction of Benzoylformic Acid in 1-Ethyl-3-methylimidazolium Bromide Room Temperature Ionic Liquid

The chemical industry is under considerable pressure to replace many volatile organic compounds that are widely used as solvents in organic synthesis. This trend leads to the exploration for novel reaction media. Room temperature ionic liquids as environmentally benign media for organic synthesis and catalytic reactions have been gradually recognized and accepted Owing to their unique chemical and physical properties, ionic liquids become promising candidates as recyclable reaction media for “ Green” applications. These nonvolatile solvents have been used as media or catalysts in dozens of fields, such as organic synthesis, organometallic catalytic reactions, separation and extraction processes.     

Carbazole-based donor-acceptor compounds: highly fluorescent organic nanoparticles

Carbazole-based donor-acceptor compounds 1,2-dicyano-trans-1,2-bis-4-(carbazolyl)phenylethylene (1) and 1,2-dicyano-trans-1,2-bis-4-(3,6-di-tert-butylcarbazolyl)phenylethylene (2) were synthesized. 1 and 2 show negative solvatochromic absorption behavior, but show both positive and negative solvatochromic behavior in the fluorescence spectra. In a water/THF mixture, 1 as well as 2 aggregate into 50-150 nm nanoparticles. The emission of nanoparticles of the new types of fluorescent organic nanoparticles (FONs) 1 and 2 is much higher than that of either 1 or 2 in solution.     

Synthesis of 3-aryl-4-methyl-1,2-benzenedisulfonimides, new chiral Brønsted acids. A combined experimental and theoretical study

We have recently reported the use, in catalytic amounts, of 1,2-benzenedisulfonimide as a safe Brønsted acid in some acid-catalyzed organic reactions. With the design of new and chiral acid organocatalysts with the structure of 1,2-benzenedisulfonimide in mind, we herein propose a synthesis of 1,2-benzenedisulfonimide derivatives bearing an aryl group in the 3-position with good overall yields. The chirality of these compounds is due to the hindered rotation of the aryl group (atropisomerism). We resolved the atropisomers of one of these compounds.     

小分子伯胺催化异噁唑有氧还原开环反应(英文)

有机催化是催化领域的前沿.在水介质中,以水合肼作为还原剂研究了小分子有机胺催化3-甲基蒽醌-[1,2-c]-异噁唑有氧还原开环反应高效合成1-氨基-2-乙酰基蒽醌,详细考察了不同种类有机胺对异噁唑有氧还原开环反应的催化性能,发现小分子有机伯胺具有很好的还原开环催化性能.在1倍水合肼存在下室温反应3 h,3-甲基蒽醌-[1,2-c]-异噁唑转化率和目标产物1-氨基-2-乙酰基蒽醌选择性均可达到97.2%.产物的分子结构经氢核磁谱和质谱得以确证.此外,提出了小分子有机伯胺催化3-甲基蒽醌-[1,2-c]-异噁唑有氧还原开环反应合成1-氨基-2-乙酰基蒽醌的可能反应机理.     

Directed Asymmetric Nickel-Catalyzed Reductive 1,2-Diarylation of Electronically Unactivated Alkenes

Transition-metal catalyzed intermolecular 1,2-diarylation of electronically unactivated alkenes has emerged as an extensive research topic in organic synthesis. However, most examples are mainly limited to terminal alkenes. Furthermore, transition-metal catalyzed asymmetric 1,2-diarylation of unactivated alkenes still remains unsolved and is a formidable challenge. Herein, we describe a highly efficient directed nickel-catalyzed reductive 1,2-diarylation of unactivated internal alkenes with high diastereoselectivities. More importantly, our further effort towards enantioselective 1,2-diarylation of the unactivated terminal and challenging internal alkenes is achieved, furnishing various polyarylalkanes featuring benzylic stereocenters in high yields and with good to high enantioselectivities and high diastereoselectivities. Interestingly, the generation of cationic Ni-catalyst by adding alkali metal fluoride is the key to increased efficiency of this enantioselective reaction.