Syntheses of sulfoxide derivatives in the benzodiazine series. Diazines. Part 37

Syntheses of new sulfinylcinnolines, quinoxalines, quinazolines and phtalazines have been investigated starting from the appropriate halogenobenzodiazine derivatives. The latter were converted in one step to the corresponding sulfanyl benzodiazines which upon oxidation with m-CPBA led to the corresponding sulfoxide derivatives of benzodiazines in moderate to good yields. In parallel to this study, an improved method for the synthesis of 2-methylsulfinylquinoxaline starting from 2-sulfanylquinoxaline is also described and in the quinazoline series a synthetic route has been developed to prepare 2-tert-butyl-5-phenylsulfinylquinazoline with satisfactory yield as well as 2-tert-butyl-5-tert-butylsulfinyl-4(3H)-quinazolinone and 2-tert-butyl-8-tert-butylsulfinyl-4(3H)-quinazolinone.     

A new route to arglecin by metalation and cross coupling of pyrazines. Metalation of diazines. XII

The metalation of dihalogeno and halogenomethoxypyrazines was performed. The resulting pyrazines were submitted to a cross-coupling reaction with propargyl alcohol followed, after dehydration, by a catalytic reduction. This gives a new route to the synthesis of a key intermediate in the synthesis of arglecin.     

Synthesis of pyrazine alcaloids from Botryllus leachi. Diazines 43

[reaction: see text] Regioselective metalation of pyrazines and cross-coupling reactions provides an easy access to botryllazines A and B and to an isomer of botryllazine A with good yields from chloropyrazine.     

Etude de proprietes physico-chimiques de l'hydrure d'aluminium

Journal of Thermal Analysis and Calorimetry - L'hydrure d'aluminium exempt de solvant a pu Être préparé avec une bonne pureté, et sa stabilité thermique a...     

Études calorimétriques en milieu solvant organique: II Enthalpies de dissolution et de dilution du boranate de lithium (LiBH4) et de l'alanate de lithium (LiAlH4) dans le tétrahydrofuranne

The enthalpies of dissolution and dilution of LiBH₄ and LiAlH₄ in THF have been determined.Dissolutions are exothermic. The endothermic dilution of LiAlH₄ suggests for this compound, either a dissociation or an association equilibrium.     

Metallation of diazines. III. New synthesis of analogues of trimethoprim and of bacimethrin

4-Chloro-2,6-dimethoxypyrimidine was lithiated by lithium 2,2,6,6-tetramethylpiperidide. The resulting lithio derivative was submitted to reaction with carbonyl derivatives, iodine and trimethyltin chloride. Synthesis of analogues of trimethoprim and of bacimetrin are reported.     

Diazines. IX. Metalation of 2-chloro, 2-methoxy and 2-pivaloylaminoquinoxaline

The lithiation of 2-chloro, 2-methoxy and 2-pivaloylaminoquinoxaline was studied. In the case of 2-chloro and 2-methoxyquinoxaline the simultaneous formation of dimers could not be avoided. The resulting lithio derivatives were reacted with carbonyl compounds and iodine. Yields in excess of 50% were obtained.     

Analytic approximations of queues with lightly- and heavily-correlated autoregressive service times

We consider a single-server queueing system. The arrival process is modelled as a Poisson process while the service times of the consecutive customers constitute a sequence of autoregressive random variables. Our interest into autoregressive service times comes from the need to capture temporal correlation of the channel conditions on wireless network links. If these fluctuations are slow in comparison with the transmission times of the packets, transmission times of consecutive packets are correlated. Such correlation needs to be taken into account for an accurate performance assessment. By means of a transform approach, we obtain a functional equation for the joint transform of the queue content and the current service time at departure epochs in steady state. To the best of our knowledge, this functional equation cannot be solved by exact mathematical techniques, despite its simplicity. However, by means of a Taylor series expansion in the parameter of the autoregressive process, a “light-correlation” approximation is obtained for performance measures such as moments of the queue content and packet delay. We illustrate our approach by some numerical examples, thereby assessing the accuracy of our approximations by simulation. For the heavy correlation case, we give differential equation approximations based on the time-scale separation technique, and present numerical examples in support of this approximation.