α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 2: Functionalisation via directed ortho-metallation and cross-coupling reactions

The functionalisation of the title compounds via regioselective Directed ortho-Metallation (DoM) and cross-coupling reactions is studied. The compatibility of the 3,7-DiOxa-r-1-AzaBicyclo[3.3.0]Oct-c-5-ylmethoxy system (DOABO-CH₂O) to typical reaction conditions is established. Its role as Directed ortho-Metallation Group (DoMG) is examined, including competition with classical DoMGs, chlorine and methoxy. The chelating ability of some functionalised terms such as DOABO-CH₂O substituting chiral diarylmethanols and polyaza analogues of 2,6-terpyridine is discussed as intramolecular steric relationships determining configuration and aptitude to bind selectively transition metals, respectively.     

First functionalization by metallation of the pyridine moiety of pyridopyrimidin-4(3H)-ones. Diazines. Part 36

Starting from o-aminopyridine carboxylic acids, a general synthetic route leading to various pyridopyrimidin-4(3H)-ones is described. The first metallation and functionalization of the pyridine moiety has been studied and a regioselective metallation at the peri-position C₅ of the pyridine ring has been highlighted.     

α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 1: Synthesis and stereochemistry. Extension to s-triazine series

The general and efficient synthesis of the title compounds, consisting of the (selective) replacement of chlorine in commercial α-chlorodiazines and cyanuryl chloride by the 3,7-dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy group (Williamson method) is described. The stereochemistry of this new series of derivatives is analysed in terms of different conformational chirality exhibited in solution (¹H NMR) versus solid state (X-ray diffractometry), meso against chiral forms, respectively. In solid state, the inclusion capacity of some chiral networks as well as their supramolecular aggregation is pointed out. A good correlation between rotameric behaviour of the c-5-di(s-tri)diazinyloxymethyl group in the two states is found.     

Metalation of bromodiazines. Diazines XL

The syntheses of 2‐bromopyrazine, 2,4‐dibromopyrimidines, and 3‐bromo‐6‐phenylpyrazine were improved and their metalation with lithium alkylamides was studied.     

A Functional Central Limit Theorem for a Markov-Modulated Infinite-Server Queue

We consider a model in which the production of new molecules in a chemical reaction network occurs in a seemingly stochastic fashion, and can be modeled as a Poisson process with a varying arrival rate: the rate is λ _i when an external Markov process J(?) is in state i. It is assumed that molecules decay after an exponential time with mean μ ^?1. The goal of this work is to analyze the distributional properties of the number of molecules in the system, under a specific time-scaling. In this scaling, the background process is sped up by a factor N ^α , for some α>0, whereas the arrival rates become N λ _i , for N large. The main result of this paper is a functional central limit theorem (F-CLT) for the number of molecules, in that, after centering and scaling, it converges to an Ornstein-Uhlenbeck process. An interesting dichotomy is observed: (i) if α > 1 the background process jumps faster than the arrival process, and consequently the arrival process behaves essentially as a (homogeneous) Poisson process, so that the scaling in the F-CLT is the usual \(\sqrt {N}\), whereas (ii) for α≤1 the background process is relatively slow, and the scaling in the F-CLT is N ^1?α/2. In the latter regime, the parameters of the limiting Ornstein-Uhlenbeck process contain the deviation matrix associated with the background process J(?).     

Metallation of diazines. V. Synthesis of analogues of biologically active molecules

2-Chloro-4-methoxypyrimidine was lithiated by lithium 2,2,6,6-tetramethylpiperidide. The resulting lithio derivative was reacted with carbonyl derivatives and iodine. Synthesis of analogues of biologically active molecules is reported.     

Metallation of diazines II. First metallation of pyridazine,metallation of 2,4-dichloropyrimidine

3,6-Dichloropyridazine was ortho-lithiated by lithium 2,2,6,6-tetramethylpiperidide. The resulting lithio compound was reacted with carbonyl derivatives iodine and trimethylchlorosilane. An azaxanthone was synthesised. An unusual regioselectivity for the lithiation of 2,4-dichloropyrimidine was studied.     

Études calorimétriques en milieu solvant organique IV. Dissociation de LiAlH4 dans le tétrahydrofuranne

From calorimetric measurements a model of solution is proposed for LiAlH₄ in THF. It is ionised as LiAlH₄ ? Li⁺ + AlH^?₄. For this reaction, ΔH_i = 3.05 kcal mol^?1 and the dissociation constant is K = 0.11.     

Solid-phase syntheses of 6-arylpyridazin-3(2H)-ones

The 3-chloropyridazine moiety was immobilized on a Wang resin, using two different methodologies. The first of these involved direct nucleophilic substitution of 3,6-dichloropyridazine with the alcoholate of Wang resin. The experimental conditions were optimized. The second method involved a Mitsunobu reaction between the Wang resin and 6-chloropyridazin-3-ol during which a problem of regioselectivity was observed. The so-obtained chloropyridazine-containing resins were subsequently reacted with various arylboronic acids under Suzuki conditions. Acid cleavage yielded 6-arylpyridazin-3(2H)-ones with high chemical purity.     

Regioselectivite de la reduction de tropones de la quinoxaline

The reduction of quinoxalinotropones by some borohydrides is studied. We calculate the electronic structures, ab initio STO 3G method, of the various possible complexes and compare to the α-enones. It is demonstrated that the borohydride reduction of these tropones is under orbital frontier control and that the important element is carbonyl complexation by the cation.