Alkylation des pyrimidines en catalyse par transfert de phase

We report here the first operationally simple and efficient study concerning the phase transfer catalysed alkylation of ambident pyrimidine dianions derived from uracil, thymine, 5-nitrouracil, 5-fluorouracil, 6-chlorouracil, 1,2,3,4-tetrahydro-2,4-dioxoquinazoline, giving selectively the corresponding N₁,N₃-dialkyl derivatives in high yield.     

Alkylation d'anions ambidents en catalyse par transfert de phase. Cas des hydroxypyridines

Alkylation of ambident-anions derived from 2- and 4-pyridones yield by phase transfer catalysis, 80% of N-substitution and 20% of O-substitution. Change of salts, solvents, temperature and alkyl halide do not interfere very much with the N- and O-alkylation percentage of substitution. Overall yields range from 40 to 80% with primary or secondary alkyl halides.     

Alkylation de la dimethyl-5 5′ isoxazolidinone-3 en catalyse par transfert de phase

Alkylation by phase transfert catalysis of ambidents anions of the N-C-0 type, leads to a mixture of N and O substitution. Isomers per cent are 20% for O alkylation and 80% for N alkylation when primary halides are used. With secondary halides, these figures are 35% and 65%. In both cases the overall yield ranges around 60%.     

Synthèse d'hétérocycles en catalyse par transfert de phase

A general study of the chemical behavior of heterocyclic anions, dianions and dianionic reagents under phase transfer catalysis conditions allowed us to synthesize various heterocyclic compounds such as imidazo[2,1-b]thiazole and derivatives; imidazo[2,1-b]thiazine and imidazo[2,1-b]benzothiazepine. Reaction conditions e.g., catalyst, solvent, temperature, etc., are indicated.     

Synthèse de pyrimidines et purines adamantylées par alkylation régiosélective directe,en catalyse par transfert de phase

The use of 1-adamantyl bromomethyl ketone, under phase transfer catalysis conditions permits the regioselective N₁ alkylation of uracil and thymine,the N₁,N₃ dialkyl derivatives. The observed selectivity is discussed in relaxation with the structure of the alkylating agent.     

Orientation de la réaction d'alkylation des pyrazoles dans des conditions neutres et en catalyse par transfert de phase

The n-butylation and N-benzylation of nine pyrazoles bearing different substituents in positions 3 and 5 have been studied in neutral and basic medium (phase transfert catalysis). The orientation of the reaction depends strongly on the method used when the position 3 (or 5) of the starting pyrazole bears a substituent with a lone pair in ortho position (pyrazolyl or pyridyl). The different products have been identified by proton nmr.     

Synthese d'ethers et de thioethers allyliques fluores par catalyse par transfert de phase

Several fluorinated allylic ethers, thioethers and diethers have been prepared in excellent yields by phase transfer catalysis (CTP). The used halogenated compounds are allyl chloride and bromide, p-chloromethylstyrene. The used fluorinated alcohols are aromatic pentafluorophenol and various aliphatics: CF₃CH₂OH, CF₂HCF₂CH₂OH ClCF₂CF₂CH₂OH,C₆F₁₃C₂H₄OH, HOCH₂CF₂CFClCF₂CH₂OH and HOC₆H₄C(CF₃)₂C₆H₄OH. All these new compounds have been characterized by ¹H and ¹³C NMR. We conclude that CTP is the best method to obtain allylic and diallylic compounds.     

Alkylation en catalyse par transfert de phase d'une série d'acridanone-9 substituées: Compétition entre O- et N-alkylation

Substituted acridanones were alkylated under phase transfer catalysis conditions. In so doing, a mixture of O- and N-alkyl derivatives was prepared. Orientation of the reaction products depends upon the alkylating agent but not on the position of the substituent. Hence, HSAB principles can explain this orientation.     

Evidence d'un mecanisme de catalyse par transfert monoelectronique (ETC) pour la reaction de cannizzaro,en phase heterogene,en conditions sonochimiques

Additional evidence about an Electron Transfer Catalysis Mechanism (ETC) in the Cannizzaro reaction, catalyzed by solid bases under sonochemical conditions is shown. The reducing sites of basic solids and the ultrasound act in the first step of the ETC mechanism.     

Catalyse par transfert de phase solide/liquide en l'absence de solvant

Solvent-free solid/liquid-phase-transfer catalysis. In this paper, we are describing the influence of the phase-transfer catalyst in heterogeneous medium on the yield of some anionic, bimolecular reactions such as the Michael and Baylis–Hillman reactions.     

Contribution à l'étude du système quaternaire KCI-RbCI-H2O: I. Les isothermes de 25° des systèmes ternaires limites

The three ternary limiting isotherms of the system KCI-RbCI-CsCI-H₂O are given for 25°. The system KCI-RbCI-H₂O, with only one solid phase present, belongs to the type I of the ROOZEBOOM classification. A large miscibility gap is present in the systems RbCI-CsCI-H₂O and KCI-CsCI-H₂O; in the latter the incorporation is almost negligible; they belong to ROOZEBOOM 's type IV.     

Etude des systèmes binaires formées par le chlorure de cyanogène et par les tétrachlorures de carbone,de silicium,de germanium et d'étain

Study of binary systems formed by cyanogen chloride and the tetrachlorides of carbon, silicon, germanium and tin. The diagrams of binary mixtures of cyanogene chloride with the tetrachlorides of carbon, silicon, germanium and tin were studied. Only SnCl₄ gives an addition compound: SnCl₄ · 2ClCN. The existence of the complex was confirmed by X-ray diffraction and vapour pressure measurements. This complex gives SnCl₄ · 2NOCl on treatment with nitrosyl chloride.     

Equation de Karplus appliquée à des systèmes sp2–sp3

A method of best fitting for the calculation of vicinal coupling constants is presented for sp²-sp³ systems. Results for 68 vicinal coupling constants from 32 different products are presented. We obtain the best Karplus-type equation to date with a dispersion factor of 31,01%.     

Alkylation de terpenes en deux etapes par ene-reaction

A simple, two-step homologation of terpenes is reported that requires ene-reaction with PhSO₂NSO and subsequent alkylation of the intermediate adducts with Cu¹ catalyzed Grignard reagents.     

S-Alkylation en série hétérocyclique par catalyse par transfert de phase: thioalkyl-2-thiazoles,thioalkyl-2-Δ-4-thiazolines et thioalkyl-2-benzothiazoles

S-Alkylation in heterocyclic serie by phase transfer catalysis: 2-alkylthiothiazoles, 2-alkylthio-Δ-4-thiazolines and 2-alkylthiobenzothiazoles Some Δ-4-thiazoline-, thiazolidine-, and benzothiazoline-2-thiones have been S-alkylated by phase transfer catalysis; yields averaged 80 to 90%. With halogenated heterocyclic compounds of poor reactivity, the main reaction consisted in a dequaternization of the catalyst by the thiones acting as nucleophiles.