1-Amino-2-hydrazinopyrimidin-N-ylides. Unusual tautomers of 1-aminopyrimidin-2-hydrazones

Summary 1-Amino-2-methylthiopyrimidinium iodides3 have been synthesized by reaction of 3-isothiocyanato-2-propeniminium perchlorates1 with hydrazines and subsequent methylation of the resulting 1-amino-2(1H)-pyrimidinthiones2. Reaction of3 with hydrazine causes substitution of the methylthio group and results in the formation of deeply coloured 1-amino-2-hydrazinopyrimidin-N-ylides5 as unusual tautomers of the commonly expected 1-amino-2(1H)-pyrimidinhydrazones4. The structure of these N-ylides has been proved by spectroscopic methods as well as by subsequent transformation to 3-amino-1,2,4-triazolo[2,3-a]pyrimidinium salts9 by dehydration or to pyrimidotriazinium salt10 c by oxidation. Reaction of N,N-disubstituted 1-amino-2-methylthiopyrimidinium salt7 a with hydrazine also causes substitution of methylthiol, the resulting orange N,N-disubstituted 1-amino-2(1H)-pyrimidinhydrazone8 a, however, cannot tautomerize to N-ylides.

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1-Amino-2-hydrazinopyrimidin-N-ylide. Ungewöhnliche Tautomere von 1-Aminopyrimidin-2-hydrazonen

Zusammenfassung Es wurden 1-Amino-2-methylthiopyrimidiniumjodide3 ausgehend von 3-Isothiocyanato-2-propeniminiumperchloraten1 und Hydrazinen durch Methylierung der primär gebildeten 1-Amino-2(1H)-pyrimidinthione2 hergestellt. Die Reaktion dieser Pyrimidiniumsalze3 mit Hydrazin verläuft unter Substitution der Methylthiogruppe unter Bildung violett gefärbter 1-Amino-2-hydrazinopyrimidin-N-ylide5 als ungewöhnliche Tautomere der allgemein erwarteten 1-Amino-2(1H)-pyrimidinhydrazone4. Die Struktur dieser Ylide5 wird durch spektroskopische Methoden sowie durch nachfolgende Dehydratisierung zu 3-Amino-1,2,4-triazolo[2,3-a]pyrimidiniumsalzen9 bzw. Oxydation zum Pyrimidotriaziniumsalz10 c bewiesen. Die Reaktion des N,N-disubstituierten 1-Amino-2-methylthiopyrimidiniumsalzes7 a mit Hydrazin verläuft ebenfalls unter Substitution der Methylthiogruppe. Jedoch kann das gebildete orange gefärbte, N,N-disubstituierte 1-Amino-2(1H)-pyrimidinhydrazon8 a nicht zu einem N-Ylid tautomerisieren.

     

Characteristics of a gold-doped electrode for application in high-performance lithium-sulfur battery

Bulk sulfur incorporating 3 wt% gold nano-powder is investigated as possible candidate to maximize the fraction of active material in the Li-S battery cathode.The material is prepared via simple mixing of gold with molten sulfur at 120℃,quenching at room temperature,and grinding.Our comprehensive study reports relevant electrochemical data,advanced X-ray computed tomography(CT)imaging of the positive and negative electrodes,and a thorough structural and morphological characterization of the S:Au 97:3 w/w composite.This cathode exhibits high rate capability within the range from C/10 to 1C,a maximum capacity above 1300 mAh gs^-1,and capacity retention between 85%and 91%after 100 cycles at 1C and C/3 rates.The novel formulation enables a sulfur fraction in the composite cathode film as high as 78 wt%,an active material loading of 5.7 mg cm^-2,and an electrolyte/sulfur(E/S)ratio of 5μL mg^-1,which lead to a maximum areal capacity of 5.4 mAh cm^-2.X-ray CT at the micro-and nanoscale reveals the microstructural features of the positive electrode that favor fast conversion kinetics in the battery.Quantitative analysis of sulfur distribution in the porous cathode displays that electrodeposition during the initial cycle may trigger an activation process in the cell leading to improved performance.Furthermore,the tomography study reveals the characteristics of the lithium anode and the cell separator upon a galvanostatic test prolonged over 300 cycles at a 2C rate.     

Dimroth-rearranged products in the reactions of 1-aryl-2-methylthiopyrimidinium salts with hydrazines

Reaction of 1-aryl-2-methylthiopyrimidinium salts with hydrazine does not lead to substitution at C-2 but to rearrangement into 1,2-diaminopyrimidinium salts. An ANRORC-mechanism involving an azatriene as intermediate is proposed.     

A tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte for advanced lithium ion batteries

Tetraethylene glycol dimethylether-lithium bis(oxalate)borate (TEGDME-LiBOB) electrolyte is here studied. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the electrolyte has conductivity higher than 10^− 3 S cm^− 1 at room temperature and about 10^− 2 S cm^− 1 at 60 °C, while thermogravimetry indicates a stability extending up to 180 °C. Sweep voltammetry of the electrolyte shows anodic stability extending over 4.6 V vs. Li and cathodic peak at about 1.5 V vs. Li/Li⁺, caused by a decomposition of LiBOB salt, and following prevented by using a pre-treated Sn-C anode. Furthermore, LiFePO₄ electrode is successfully used as cathode in a lithium cell using the TEGDME-LiBOB electrolyte. The promising electrochemical results, the low cost and the very high safety level candidate the electrolyte here reported as a valid alternative to the conventional electrolyte based on fluorinated salts presently used in the lithium ion battery field.     

96 mW longitudinal single mode red-emitting distributed Bragg reflector ridge waveguide laser with tenth order surface gratings

Red-emitting ridge waveguide lasers with integrated tenth order surface distributed Bragg reflector gratings were developed. The grating was implemented by the use of a BCl3-Ar-plasma, while the shape of the grating trench was controlled by additional He-backside cooling of the wafer. The devices exhibit longitudinal single mode operation up to 96 mW at 635.3 nm with a side mode suppression ratio of 18 dB and a good beam quality of M2<3. The spectrum is free of mode hops for a span of more than 55 pm.