Untersuchung der Thermolysereaktion von Malonsäuremonoarylestern

Thermolysis of malonic acid monoaryl esters gives rise to the formation of a steady-state equilibrium with diaryl malonates and free malonic acid, the latter being decarboxylated to form acetic acid. The yields of diaryl malonates are lowered by a concurrent reaction, namely the decarboxylation of the monoesters, giving aryl acetates and CO₂.

---

---

Mit 2 Abbildungen

---

H. Junek, E. Ziegler, U. Herzog undH. Kroboth, Synthesis1976, 332.     

Erratum

Ohne Zusammenfassung

---

Erratum

     

Eine verbesserte Synthese von Thiaminmonochlorid

Starting from the hydrochloride of vitamin B₁, thiamin monochloride is prepared simply by use of sodium bicarbonate and sodium chloride in aqueous solution.

Herrn Prof. Dr.Erich Ziegler, Graz, mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Stereoconservative Negishi arylation and alkynylation as an efficient approach to enantiopure 2,2'-diarylated 1,1'-binaphthyls

Negishi arylation and alkynylation of easily synthesized chiral 2,2'-diodo-1,1'-binaphthyl rapidly proceeds in refluxing THF utilizing controlled microwave irradiation, affording enantiopure 2,2'-diarylated 1,1'-binaphthyls in good to excellent yields.     

Optical sensor for salicylic acid and aspirin based on a new lipophilic carrier for aromatic carboxylic acids

Summary The optode with fair selectivity for salicylate and aspirin is based on the use of a new lipophilic carrier for aromatic carboxylic acids, namely (±) n-butyl O-(1-naphthylaminocarbonyl) lactate (BNAL). The sensing scheme involves co-extraction of both salicylate anion and a proton from the aqueous sample medium into a pvc layer using BNAL as a salicylate carrier, and a pH-sensitive dye as a lipoid proton carrier, both contained in the pvc membrane. BNAL transports the salicylate anion into the pvc lipid membrane. In order to maintain electro-neutrality, the proton carrier dye simultaneously extracts a proton into the pvc membrane, thereby becoming protonated. As a result, the dye undergoes a colour change which is detected via measurement of fluorescence intensity. The sensor is fully reversible and has a dynamic range from 0.1 to 30 mmol/l salicylate at pH 5.00, but the response function is highly pH-dependent. The effect of 25 interfering anions was investigated, and optical selectivity coefficients were determined. It is also shown that by proper variation of the membrane composition, selectivities for other carboxy anions can be obtained. The method has been applied to determine aspirin in tablets using flow injection analysis, and the results were found to be satisfactory.On leave of absence from the Department of Chemistry, Nankai University, CN-300071 Tianjin, P. R. China     

Fluorescent 6‐hydroxy‐ and 6,7‐dihydroxy‐4‐trifluoro‐methylcarbostyrils and formation of o‐carboxymethylated derivatives via o‐succinimide esters

Stepwise demethylation of fluorescent 6,7‐dimethoxy‐3‐trifluoromethylcarbostyrils 5 leads to 6‐hydroxy derivatives 6 and 6,7‐dihydroxyderivative 7 . Phenolate formation shifts excitation and emission maxima from 370 and 430 nm to 430 and 480 nm for the anion of 6 and as far as 500 and 580 nm for the dianion of 7 . Dependence of fluorescence quantum yield on media and polar structure, varying from 0.02 to 0.51, is discussed. O‐Alkylation of 6 with alkyl bromoacetate yields esters of type 8 in good yield. Reactive succinimidoyl (OSu) esters of type 11 were prepared after saponification to acids 9 . With amino acids or their esters, peptides and aminoglucose, linking to labeled derivatives 13 or 15 could be achieved under mild conditions in slightly basic aqueous media.     

Synthesis and pancreatic lipase inhibitory activities of some 1,2,4-triazol-5(3)-one derivatives

In this study, starting from 4-amino-5-(4-chlorobenzyl)-2,4-dihydro-3H-1,2,4-triazole-3-one ( 1 ), the 4-Amino-5-(4-chlorobenzyl)-2-undecyl-2,4-dihydro-3H-1,2,4-triazol-3-one ( 2 ) was first synthesized and this compound was converted to Schiff base derivatives ( 3a-e ). In the second step of the study, the 2-[3-(4-chlorobenzyl)-5-oxo-1-undecyl-1,5-dihydro-4H-1,2,4-triazole-4-yl]-acetohydrazide ( 6 ), which was used as a key product in the synthesis of many heterocyclic compounds was synthesized in four steps, and then this compound was converted into methylidene acetohydrazide ( 7a-e ), thiosemicarbazide ( 8a-e ), and 1,2,4-triazole-5-thione ( 9a-e ) derivatives. Also, in the last part of the study, 1,2,4-triazole-5-thione derivatives were changed into Mannich bases ( 10a-b ) bearing a 4-phenylpiperazine ring. These new compounds were tested with regard to pancreatic lipase (PL) inhibition activity, and compound 3b , 3d , 7d , 8d , and 9d showed a considerable anti-lipase activity at various concentrations. The activity of compounds 7b (IC₅₀ = 1.45 ± 0.12 μM) was the highest in terms of IC₅₀, comparable to that of orlistat, a well-known PL inhibitor used as an antiobesity drug.     

New integer linear programming formulation for the traveling salesman problem with time windows: minimizing tour duration with waiting times

The travelling salesman problem, being one of the most attractive and well-studied combinatorial optimization problems, has many variants, one of which is called ‘travelling salesman problem with Time Windows (TSPTW)’. In this problem, each city (nodes, customers) must be visited within a time window defined by the earliest and the latest time. In TSPTW, the traveller has to wait at a city if he/she arrives early; thus waiting times directly affect the duration of a tour. It would be useful to develop a new model solvable by any optimizer directly. In this paper, we propose a new integer linear programming formulation having O(n²) binary variables and O(n²) constraints, where (n) equals the number of nodes of the underlying graph. The objective function is stated to minimize the total travel time plus the total waiting time. A computational comparison is made on a suite of test problems with 20 and 40 nodes. The performances of the proposed and existing formulations are analysed with respect to linear programming relaxations and the CPU times. The new formulation considerably outperforms the existing one with respect to both the performance criteria. Adaptation of our formulation to the multi-traveller case and some additional restrictions for special situations are illustrated.     

Experimental realizations of the HR neuron model with programmable hardware and synchronization applications

This study presents experimental realizations of the HR neuron model with programmable hardware and synchronization applications. The HR neuron model exhibiting burst, spike, and chaotic dynamics has been implemented with both FPAA (Field Programmable Analog Array) and FPGA (Field Programmable Gate Array) devices. These devices provide flexible design possibilities such as reducing the complexity of design, real-time modification, software control and adjustment within the system. And it is also examined experimentally that how the synchronization of two HR neurons are able to achieve by using these hardware. The experimental results obtained from FPAA and FPGA based realizations agree with the numerical simulations very well.