The First Mitsunobu Protocol for Efficient Synthesis of α-Acyloxyphosphonates Using 4,4′-Azopyridine

Abstract

This is the first report on applying the Mitsunobu protocol for the synthesis of various α-acyloxyphosphonates using 4,4′-azopyridine and PPh₃ with diverse aromatic and aliphatic carboxylic acids. Under these conditions, diethyl azodicarboxylate (DEAD) as the traditional reagent for Mitsunobu reaction is not efficient. The insoluble pyridine hydrazine byproduct can be simply isolated and recycled to its azopyridine by an oxidation reaction and reused again.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Characterization data of compounds 3a–3z2 and NMR spectra.]

GRAPHICAL ABSTRACT      

New Polydentate Trimethylsilyl Chalcogenide Reagents for the Assembly of Polyferrocenyl Architectures

A series of polychalcogenotrimethylsilane complexes Ar(CH₂ESiMe₃)_n, (Ar=aryl; E=S, Se; n=2, 3, and 4) can be prepared from the corresponding polyorganobromide and M[ESiMe₃] (M=Na, Li). These represent the first examples of the incorporation of such a large number of reactive ?ESiMe₃ moieties onto an organic molecular framework. They are shown to be convenient reagents for the preparation of the polyferrocenylseleno‐ and thioesters from ferrocenoyl chloride. The synthesis, structures, and spectroscopic properties of the new silyl chalcogen complexes 1,4‐(Me₃SiECH₂)₂(C₆Me₄) (E=S, 1 ; E=Se, 2 ), 1,3,5‐(Me₃SiECH₂)₃(C₆Me₃) (E=S, 3 ; E=Se, 4 ) and 1,2,4,5‐(Me₃SiECH₂)₄(C₆H₂) (E=S, 5 ; E=Se, 6 ) and the polyferrocenyl chalcogenoesters [1,4‐{FcC(O)ECH₂}₂(C₆Me₄)] (E=S, 7 ; E=Se, 8 ), [1,3,5‐{FcC(O)ECH₂}₃(C₆Me₃)] (E=S, 9 ; E=Se, 10 ) and [1,2,4,5‐{FcC(O)ECH₂}₄(C₆H₂)] (E=S, 11 illustrated; E=Se, 12 ) are reported. The new polysilylated reagents and polyferrocenyl chalcogenoesters have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ⁷⁷Se), electrospray ionization mass spectrometry and, for complexes 1 , 2 , 3 , 4 , 7 , 8 , and 11 , single‐crystal X‐ray diffraction. The cyclic voltammograms of complexes 7 – 11 are presented.     

A new liquid-phase microextraction method based on solidification of floating organic drop

In the present study, a new and versatile liquid-phase microextraction method is described. This method requires very simple and cheap apparatus and also a small amount of organic solvent. Eight microliters of 1-undecanol was delivered to the surface of solution containing analytes and solution was stirred for a desired time. Then sample vial was cooled by inserting it into an ice bath for 5 min. The solidified 1-undecanol was transferred into a suitable vial and immediately melted; then, 2 μL of it was injected into a gas chromatograph for analysis.Some polycyclic aromatic hydrocarbons (PAHs) were used as model compounds for developing and evaluating of the method performance. Analysis was carried out by gas chromatography/flame ionization detection (GC/FID).Several factors influencing the microextraction efficiency, such as the nature and volume of organic solvent, the temperature and volume of sample solution, stirring rate and extraction time were investigated and optimized. The applicability of the technique was evaluated by determination of trace amounts of PAHs in environmental samples. Under the optimized conditions, the detection limits (LOD) of the method were in the range of 0.07-1.67 μg L⁻¹ and relative standard deviations (R.S.D.) for 10 μg L⁻¹ PAHs were <7%. A good linearity (r² > 0.995) in a calibration range of 0.25-300.00 μg L⁻¹ was obtained. After 30 min extraction duration, enrichment factors were in the range of 594-1940. Finally, the proposed method was applied to the determination of trace amounts of PAHs in several real water samples, and satisfactory results were resulted. Since very simple devices were used, this new technique is affordable, efficient, and convenient for extraction and determination of low concentrations of PAHs in water samples.     

High fidelity single qubit operations using pulsed electron paramagnetic resonance

Systematic errors in spin rotation operations using simple rf pulses place severe limitations on the usefulness of the pulsed magnetic resonance methods in quantum computing applications. In particular, the fidelity of quantum logic operations performed on electron spin qubits falls well below the threshold for the application of quantum algorithms. Using three independent techniques, we demonstrate the use of composite pulses to improve this fidelity by several orders of magnitude. The observed high-fidelity operations are limited by pulse phase errors, but nevertheless fall within the limits required for the application of quantum error correction.     

Efficient synthesis of symmetrical phthalate and maleate diesters using phosphinite ionic liquids

Symmetrical dialkyl phthalates and maleates were synthesized using phosphinite ionic liquid as a catalyst and reaction medium. The results indicated that phosphinite ionic liquid shows better catalytic and reusable performance without using any acid or base catalyst. Under the optimum conditions, using 1-methyl-3-(4-phosphinitebutyl) imidazolium chloride as catalyst, the conversion of phthalic and maleic anhydrides to the corresponding diesters of primary and secondary alcohols was occurred in 72?C85% yields. The diesters of tertiary alcohols and phenols could not be prepared by this method. A kind of widely used plasticizer, dioctyl phthalate, was prepared in good yield under these conditions. The ionic liquid could be reused three times after easy separation from the products without any disposal.     

Convergence analysis of the Wolf method for Coulombic interactions

A rigorous proof for convergence of the Wolf method (Wolf et al., 1999 [9]) for calculating electrostatic energy of a periodic lattice is presented. In particular, we show that for an arbitrary lattice of unit cells, the lattice sum obtained via Wolf method converges to the one obtained via Ewald method.     

Switching of global minima of novel germylenic reactive intermediates via halogens (X): C2GeH2 vs. C2GeHX at ab initio and DFT levels

For 30 C₂GeHX germylenic isomers, one cyclic structure, X-germacyclopropenylidene, and three acyclics are considered, which include: ethynyl-X-germylene, X-vinylidenegermylene, and (X-ethynyl)germylene (X = H, F, Cl, and Br). The global minimum among six isomeric C₂GeH₂ (where X = H), is found to be cyclic, aromatic, singlet germacyclopropenylidene. In contrast, among the 24 corresponding halogermylenes, C₂GeHX (where X = F, Cl, and Br), the global minima switch to acyclic, singlet ethynylhalogermylenes, at eight reasonably high ab initio and DFT levels. The direct resonance interaction between X and the divalent center Ge in the singlet acyclic ethynylhalogermylene structures, is claimed to justify switching of the calculated global minima in the halo derivatives. GIAO-NICS calculations indicate that the X-germacyclopropenylidene isomer is more aromatic for X = H than X = F, Cl, or Br. The angle ∠XGeC bending potential energy curves show the singlet and triplet ethynylgermylene crossing at ≈146°, for X = H.     

Negative optical inertia in optomechanical systems

A method of improving the sensitivity of laser-interferometer-based gravitational-wave detectors by using double (two-frequency) optical pumping is proposed. Proper selection of the optical parameters of each pump wave allows implementation of the so-called “negative inertia,” that is, an increase in the detector’s mechanical response to an external force in a wide frequency range, which is equivalent to the reduction of the inertial masses of the test bodies of the detector, while their gravitational masses remain the same. This effect allows overcoming the standard quantum limit of sensitivity for a free mass in a wide frequency range due to an enhanced signal response, rather than due to the mutual compensation of quantum noises, as in other methods. The advantage of the proposed method is its much higher immunity to the noise caused by optical losses as compared to schemes based on mutual compensation of quantum noises. A practical scheme of the gravitational-wave detector based on the “negative-inertia” effect is explored, and a set of optimal optical parameters facilitating achieving a maximum signal-to-noise ratio for the main types of astrophysical gravitational-wave sources is obtained.