New Routes to β-Iminophosphonates,Phosphineoxides, and Sulfides

Abstract

Two synthetic methods leading to β-iminophosphonates, phosphineoxides, and sulfides 2 are reported. The first method involves the reaction of imines with chlorophosphines and phosphites followed by oxidation or sulfurization. The second one utilizes the reaction of imines with diethylchlorophosphate and thiophosphate. The stereochemistry of the obtained products is discussed, and their structure is confirmed by NMR (¹H, ³¹P, ¹³C) and IR spectroscopies, and by mass spectrometry.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT      

Modular approach to saturated and α,β-unsaturated ketones

2-Fluoro-6-pyridinyloxy derivatives of 2-ethoxyvinyl carbinols react with radicals derived from xanthates by an addition-fragmentation pathway to give highly functionalized ketones after acid hydrolysis. 1,4-Diketones are readily accessible by this approach. α,β-Unsaturated ketones can be obtained by starting with geminal acetoxy xanthates prepared by addition of a simpler xanthate to vinyl acetate.     

Synthetic Approaches to α-, β-, γ-, and δ-Lycoranes

Lycorane is a pentacyclic core presented in alkaloids isolated from the Amaryllidaceae family of herbaceous flowering plants. Members of this class of natural products have shown to display important biological properties including analgesic, antiviral, and antiproliferative activities. This review presents the known synthetic routes toward α-, β-, γ-, and δ-lycoranes. α-(19 routes), β-(10 routes), γ-(38 routes), and δ-(6 routes).     

Peptide binding to β-cyclodextrins: structure, dynamics, energetics, and electronic effects

Peptide-cyclodextrin and protein-cyclodextrin host-guest complexes are becoming more and more important for industrial applications, in particular in the fields of pharmaceutical and food chemistry. They have already deserved many experimental investigations although the effect of complex formation in terms of peptide (or protein) structure is not well-known yet. Theoretical calculations represent a unique tool to analyze such effects, and with this aim we have carried out in the present investigation molecular dynamics simulations and combined quantum mechanics-molecular mechanics calculations. We have studied complexes formed between the model Ace-Phe-Nme peptide and the β-cyclodextrin (β-CD) macromolecule, and our analysis focuses on the following points: (1) how is the peptide structure modified in going from bulk water to CD environment (backbone torsion angles), (2) which are the main peptide-CD interactions, in particular in terms of hydrogen bonds, (3) which relative peptide-CD orientation is preferred and which are the structural and energetic differences between them, and (4) how the electronic properties of the peptide changes under complex formation. Overall, our calculations show that in the most stable configuration, the backbone chain lies in the narrow rim of the CD. Strong hydrogen bonds form between the H atoms of the peptidic NH groups and oxygen atoms of the secondary OH groups in the CD. These and other (weaker) hydrogen bonds formed by the carbonyl groups reduce considerably the flexibility of the peptide structure, compared to bulk water, and produce a marked increase of the local dipole moment by favoring configurations in which the two C═O bonds point toward the same direction. This effect might have important consequences in terms of the peptide secondary structure, although this hypothesis needs to be tested using larger peptide models.     

Four‐Component Cyclocondensation of Aminodiazines,Glyoxal, Formaldehyde,and Methanol to Imidazolidines

Four‐component reaction of aminodiazines (2‐aminopyrimidine and 2‐aminopyrazine), glyoxal, formaldehyde, and methanol yields trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrimidinyl)imidazolidine (5a) and trans‐4,5‐dimetoxy‐1,3‐bis(2‐pyrazinyl)imidazolidine (5b), respectively. Changing methanol to acetonitrile leads to the formation of the corresponding 1,3‐bis(2‐pyrimidinyl) and‐1,3‐bis(2‐pyrazinyl)‐ derivatives of trans‐4,5‐dihydroxyimidazolidine (6). Details of the proposed mechanism are discussed.     

Synthesis,structure and chiroptical spectra of the bicyclic α-diketones,imides and dithioimides related to santenone

Isomeric α-diketones, imides and dithioimides related to santenone were prepared in a multistep synthesis from (+)-camphor and their CD spectra compared with those of analogous chromophoric systems related to camphor. In the case of conformationally rigid α-diketones the methyl substituents at C-7, lying on the symmetry plane of the chromophore, exert only a weak contribution to the n–π* Cotton effects. In contrast, the Cotton effect magnitudes of the anhydrides, imides and dithioimides are significantly affected by the substituents at C-8. The steric interaction of these chromophores with the syn-methyl group at C-8, leading to the chromophore distortion, was confirmed by X-ray crystallographic studies.     

From Monomers to π Stacks, from Nonconductive to Conductive: Syntheses, Characterization, and Crystal Structures of Benzidine Radical Cations

Salts that contain radical cations of benzidine (BZ), 3,3',5,5'-tetramethylbenzidine (TMB), 2,2',6,6'-tetraisopropylbenzidine (TPB), and 4,4'-terphenyldiamine (DATP) have been isolated with weakly coordinating anions [Al(OR(F) )(4) ](-) (OR(F) =OC(CF(3) )(3) ) or SbF(6) (-) . They were prepared by reaction of the respective silver(I) salts with stoichiometric amounts of benzidine or its alkyl-substituted derivatives in CH(2) Cl(2) . The salts were characterized by UV absorption and EPR spectroscopy as well as by their single-crystal X-ray structures. Variable-temperature UV/Vis absorption spectra of BZ(.) (+) [Al(OR(F) )(4) ](-) and TMB(.) (+) [Al(OR(F) )(4) ](-) in acetonitrile indicate an equilibrium between monomeric free radical cations and a radical-cation dimer. In contrast, the absorption spectrum of TPB(.) (+) SbF(6) (-) in acetonitrile indicates that the oxidation of TPB only resulted in a monomeric radical cation. Single-crystal X-ray diffraction studies show that in the solid state BZ and its methylation derivative (TMB) form radical-cation π dimers upon oxidation, whereas that modified with isopropyl groups (TPB) becomes a monomeric free radical cation. By increasing the chain length, π stacks of π dimers are obtained for the radical cation of DATP. The single-crystal conductivity measurements show that monomerized or π-dimerized radicals (BZ(.) (+) , TMB(.) (+) , and TPB(.) (+) ) are nonconductive, whereas the π-stacked radical (DATP(.) (+) ) is conductive. A conduction mechanism between chains through π stacks is proposed.     

Structural Properties of Water–PEG–LiOH,NaOH, and KOH Solutions,According to Viscometry and Densimetry Data

Russian Journal of Physical Chemistry A - The dynamic viscosity and density of water–PEG, water–PEG–LiOH, water–PEG–NaOH, and water–PEG–KOH systems are...     

Simple,Extremely Fast,and High‐Yielding Oxidation of Thiols to Disulfides

Abstract

Results of oxidation of thiols to disulfides with 1,3‐dibromo‐5,5‐dimethylhydantoin (DBDMH) are described. A simple addition of 0.20–0.25 mol equivalent of solid DBDMH to thiol in chloroform at room temperature yielded the disulfides in excellent yield. The reaction is extremely fast and gave no other oxidized side products.     

X-rays to study,induce, and pattern structures in sol–gel materials

X-rays investigations have been shown to reveal important information regarding material features and the formation mechanism of mesostructured materials. Small angle X-ray scattering (SAXS) analysis performed using a synchrotron source has been very important in the optimization of the organization of mesoporous coatings obtained by evaporation induced self-assembly (EISA). The interaction between X-rays and ordered mesoporous films has only recently been reported, and new knowledge has been developed to use this external radiation source to tune the local material properties. Here we discuss the recent developments in X-ray lithography combined with sol–gel synthesis to pattern mesostructured and hierarchical porous coatings including the ability to tailor functionalized surfaces.     

Erratum to: “Current uses and trends in catalytic isomerization, alkylation and etherification processes to improve gasoline quality”

The original version of the article was published in Cent. Eur. J. Chem. 12(1) (2014) pp. 1–13. Unfortunately, the original version of this article contains some mistakes in the text:

• The caption of Figure 7. A fixed bed unit converted to the UOP Par-Isom Process?
• Par Isom Process should be written as Par-Isom Process?
• everywhere in the text LCC should be written as LLC

     

Facile access to α,β-dehydroalanine and α,β-dehydroamino butyric acid derivatives from DL-serines and threonines

Not only α,β-dehydroamino acids are important constituents for a number of bioactive peptides in nature, but also they are important building blocks for a variety of synthetic amino acids in organic synthesis. Methods to prepare dehydroamino acids have been reported extensively in the literature; however, efficient and convenient protocols are still required. Here we have developed a convenient method to prepare dehydroalanine (ΔAla) and dehydroamino butyric acid (ΔAbu) derivatives derived from DL-serines and DL-threonines, respectively. 4-Toluenesulfonyl chloride (TsCl) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were employed in this procedure, which carried out activation of hydroxyl group and β-elimination in one pot. Because it is convenient and easy to handle, this method will attract the attention of synthetic chemists.     

Green, efficient and practical Michael addition of arylamines to α,β-unsaturated ketones

The aza-Michael addition of aromatic amines to α,β-unsaturated ketones was carried out effectively at room temperature in good to excellent yields without any catalyst or solvent. It was significant that part of adducts could be collected in almost quantitative yield without column chromatography. This procedure offered a green, efficient, and practical approach for the synthesis of β-amino ketones.     

Simple and convenient access to α,α,α-trisubstituted amides by double addition of Grignard reagents to acyl cyanohydrins

The double addition of Grignard (alkyl, aryl, alkenyl, alkynyl) reagents to acyl cyanohydrins was performed under unusually smooth conditions with a concomitant O-N acyl transfer, providing a very simple and general access to α,α,α-trisubstituted amides.     

Wine,Polyphenols, and Mediterranean Diets. What Else Is There to Say?

A considerable amount of literature has been published claiming the cardiovascular benefits of moderate (red) wine drinking, which has been considered a distinguishing trait of the Mediterranean diet. Indeed, red wine contains relevant amounts of polyphenols, for which evidence of their biological activity and positive health effects are abundant; however, it is also well-known that alcohol, even at a low level of intake, may have severe consequences for health. Among others, it is directly related to a number of non-communicable diseases, like liver cirrhosis or diverse types of cancer. The IARC classifies alcohol as a Group 1 carcinogen, causally associated with the development of cancers of the upper digestive tract and liver, and, with sufficient evidence, can be positively associated with colorectum and female breast cancer. In these circumstances, it is tricky, if not irresponsible, to spread any message on the benefits of moderate wine drinking, about which no actual consensus exists. It should be further considered that other hallmarks of the Mediterranean diet are the richness in virgin olive oil, fruits, grains, and vegetables, which are also good sources of polyphenols and other phytochemicals, and lack the risks of wine. All of these aspects are reviewed in this article.     

A facile entry to β,δ-diketo and syn-β,δ-dihydroxy esters

Reaction of N-methoxy-N-methyl amides with the dianions of acetoacetates gives β,δ-diketo esters in yields of synthetic use, and the diketo esters were selectively reduced to syn-β,δ-dihydroxy esters, key intermediates of synthetic HMG-CoA reductase inhibitors.