Préparation de cétals cycliques à plus de sept chaǐnons

A good synthesis of eight-membered cyclic ketals, among them trioxocanes, is described. These products are obtained by direct reaction of a ketone on a substitute of orthoester.     

Additions radicalaires du tétrahydrothiophène à des dérivés éthyléniques: Préparation de tétrahydrothiophènes substitués en 2

Di-t-butyl peroxide induces a free radical addition of tetrahydrothiophene to ethylenic compounds. The main products arise from an α-attack of the substrate. This reaction seems to be an interesting synthesis of these heterocycles.     

Nouvelle méthode de préparation d'éthers vinyliques à partir d'acétals

A new way to vinylic ethers from acetals Acetals react at low temperatures in presence of a Lewis acid (aluminium chloride or magnesium bromide) with tertiary amine to give in good yields the vinylic ethers corresponding to the elimination of one molecule of alcohol.     

Synthèse de nouveaux types de dérivés C-glycosyliques à partir de sucres acétyléniques ou de leurs équivalents synthétiques partiels

Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof The concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described. We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS^? with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.     

Préparation de polyesteramides alternés

The polycondensation of hydroxyamido acids of general formula HO-R₁-CO-NH-R₂-COOH provides alternating polyesteramides only when R₁ and R₂ are alkyl groups. These aliphatic alternating polyesteramides, according to their structural high regularity, possess a more important content of interchain hydrogen bonds than the random copolymers. The higher melting point of the random copolymers is attributed to the heterogeneity of amide group partition in the chain. The existence of a benzyl group in the structure of the hydroxyamido acids reduces the polycondensation ability and the molecular weights of the products are low. These aromatic monomers are thermally degraded, p-toluic acid evolving; ester and amide functions stoechiometric ratio is not maintained, but infrared and differential thermal analysis show that these aromatic polyestermides keep a reasonable structural regularity.     

Synthèse de nouveaux polyesters insaturés styrèniques à partir de diols isomoléculaires à ponts thio-éthers. Étude par RMN et tenue thermique

The synthesis of unsaturated polyesters cross-linked by means of styrene have been carried out from high isomolecular weight diols containing thio-ether bonds. The ¹H-NMR peaks have been attributed. Those polyesters exhibit softness to a certain extent in conjunction with relatively high degradation temperatures (T_d 400°C).     

Addition de la proline à quelques alcènes et alcynes électrophiles

Addition of proline in acetic anhydride to propiolic and pbenylpropiolic ester gave rise to two isomeric pyrroles 5 and 6 . Addition under the same conditions, to electrophilic alkenes pY-PhCH = C(X) (CN) led to a pyrroline-2 8 which eliminated HCN and produced pyrrole 9 . Addition of proline to fumarodinitrile is unusual, the reaction led to a new α-amino acid 10 and compound 11 . The structure of this product 11 was confirmed by X-ray measurements.     

Préparation de dérivés de sucres acétyléniques terminaux et d'acides ynuroniques par réaction de Wittig. Note de laboratoire

Synthesis of Terminal Acetylenic Sugars Derivatives and Ynuronic Acids Derivatives by Use of a Wittig Reaction The method described for the preparation of terminal acetylenic sugars presents two advantages over earlier procedures: no new asymmetric center is created and the chain can be extended by one or more C-atoms. The method also allows preparation of ynuronic acids. The aldehydosugars derivatives 1–7 gave in good to excellent yields the corresponding gem-dibromoenoses 8–14 from which either the terminal acetylenic sugars derivatives 15–21 or the ynuronic acids 22–24 were easily prepared. A few examples of 1,3-dipolar cycloadditions (leading to 28–30 ) with these acetylenic sugar derivatives are also described.     

Sur diverses possibilités de formation de pyrimidines à partir de formyl-3 chromone

Guanidine transforms the following: (a) 3-formylchromone into a mixture of 2-amino-5-(2-hydroxybenzoyl)pyrimidine and 2-amino-5H-[1]-benzopyrano[4,3-d]pyrimidine; (b) the diacetate of 3-methylidyne-chromone into 2-amino-5-hydroxy-5H-[1]benzopyrano[4,3-d]pyrimidine; and (c) the oxime of 3-formylchromone into 2-amino-5H-[1]benzopyrano-[4,3-d]pyrimidin-5-one. Thiourea, acetamidine and nitroguanidine can also generate pyrimidines of the same type with 3-formylchromone, the diacetate of 3-methylidynechromone or 3-(1,3-dioxolan)chromone.     

Sur la synthèse du pollinastanol à partir du cycloartanol

The partial synthesis of pollinastanol (14) from cycloartanol (3) is reported. The transformation proceeds through the methylenic intermediate 12; the ring enlargement with cyanogen azide affords pollinastanone (13) further reduced to 14, The 4-keto isomer of pollinastanone (17) as well as a series of 5-β isomeric compounds are also described.     

Recherches dans la série des cyclitols XLIII. Sur des éthylène-cétals de cétoses dérivés du cyclopentane

The synthesis of a series of keto derivatives of cyclopentane is described. The configurations of these derivatives have been determined by chemical methods and verified by IR. and NMR. spectroscopy. The preferred conformation of the cyclopentane part of the molecule has been established by the study of intramolecular hydrogen bonds and the values of the coupling constants J_{H? C? OH} and J_{H, H}.     

Analyse conformationnelle de cétones cyclopropaniques par RMN à l'aide des déplacements paramagnétiques induits par Eu(dpm)3

The lanthanide induced shifts (LIS) of the lanthanide shift reagent Eu(dpm)₃ are reported for several cyclopropyl ketones. The conformational preference of the cyclopropanoyl group is determined via LIS by comparison with two compounds: dispiro-[2.1.2.2]nonane-4-one and 4,4,5-trimethyl bicyclo[3.1.0]hexane 2-one which are respectively in s-cis and s-trans conformation.     

Synthèses d'hétérocycles indoliques à partir de dérivés carbonylés de l'indole et du pyrrole

The reactions of ethyl azidoacetate with 1-methylindole-2-3-dicarboxaldehyde (1) and its monoacetal 2 afforded β and γ carbolines. The regioselectivity of condensation of ethy6l aminoacetate with 1 was investigated and yields a γ-carboline. Derivatives of a new heterocycle, the thiepino[4,5-b]indole and its application of the synthesis of some carbazoles are described.     

Applications synthétiques de la cyclisation d'alcools tertiaires γ-éthyléniques en α-bromotétrahydrofurannes sous l'action du N-bromosuccinimide. I. Synthèse facile de la triméthyl-2,2,5-cycloheptène-4-one ou karahanaénone à partir du linalol

The ionic reaction of linalool and N-bromosuccinimide in CCl₄ at room temperature afforded 2-methyl-2-vinyl-5-(1-bromo-1-methyl-ethyl)-tetrahydrofuran (I). On treatment with refluxing collidine this compound yielded the intermediate allyl vinyl ether III, which immediatealy rearranged to 2,2, 5-trimethylcyclohept-4-en-one (V) or «karahanaenone» through a [3,3]-sigmatropic process. Karahanaenone, a constituent of hop oil, was thus synthesized for the first time (overall yield 62% from linalool). The mechanisms of these reactions are discussed.