Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry最新文献

Heteropolyacids (HPW) are known as active catalysts for various redox reactions. The direct incorporation of HPW species in a mesoporous organised silica molecular sieve during the synthesis was studied. The association of two type of surfactants is essential for the preparation of such solids. The silica-organised materials comprising heteropoly compounds thus obtained were thermally stable porous materials with mesopores and large surface areas.

In our program of new macrocyclic antibiotic derivatives synthesis, a natural kijamicin analog was isolated, disclosing important antibiotic and antiviral properties, which are under investigation. In this paper we describe a synthesis of the bottom half C1-C14 (n = 1) of its aglycon. This strategy was based on the preparation of a tetraene derivative via a palladium catalyzed Stille coupling reaction, the final step involving an IMDA cyclization key step.

An efficient synthesis of two analogues of huperzine A via a one-step synthesis of E alkene.

The dihydropyridine-induced reduction of alkoxycarbene complexes of chromium has been generalized to differently substituted dihydropyridines, e.g. N-benzyl dihydropyridine and N-methyl-N’N’-diethyldihydronicotinamide. In all the cases examined, alkoxyalkynyl carbene complexes lead, upon cascade insertions, to butenolides, the diastereomeric excesses being dependent on the structure of the dihydropyridines.

Boric acid has always been neglected in prebiotic chemistry, because it is not a major component of biological macromolecules. We argue here for a potential catalytic role of boric acid in peptides and nucleic acid synthesis. Today boron is an important component of seawater (0.4 mM). Its concentration at prebiotic times was probably higher. In water, boron mainly appears in the form of boric acid or its derivatives (esters and anhydrides).

By mixing an aqueous solution of antimonotungstate at pH = 4–5 and an aqueous solution of manganese(II) chloride, of cobalt(II) chloride, of nickel(II) chloride, or of zinc, a monosubstituted heteropolytungstate 〚H₃Sb^IIIM^IIW₁₇O₅₉(H₂O)〛^8– is obtained (M^II = Mn^II, Co^II, Ni^II, Zn^II). The crystallographic study, associated to EPR, XANES, EXAFS, and proton NMR spectrometries, leads to a structure identical to this of 〚H₂As^IIIW₁₈O₆₀〛^7–. There are two moieties Sb^IIIW₉O₃₀ and H₃M^IIW₈O₃₀. It is concluded that the M^II atom substitutes a tungsten atom of the belt of six octahedra perpendicular to the ternary axis of the polytungstate. The same type of compound was obtained starting from bismuth chloride and copper acetate, that is 〚H₃Bi^IIICu^IIW₁₇O₅₉(H₂O)〛^8–.

From Jean-Baptiste Dumas to Chaïm Weizmann and to Margaret Thatcher, including Alfred Naquet, Marcelin Berthelot, Auguste Scheurer-Kaster, Stanislao Cannizzaro, Frédéric Joliot etc., there are few chemists who, at one time or another, have not been tempted to enter politics. Philippe Landrieu is certainly one of the lesser known of this group, even if he had a laudatory Obituary in both the Bulletin de la Société chimique de France, and La Nouvelle Revue socialiste. The events in which he was involved, the utopias for which he was searching, his double career, and his scientific work, nothing was ordinary in his busy life. This Note, as well as placing him in the social history of the last century, will also recall his work as a chemist, and the unresolved problems in which he was interested.

Bismuth(III) salts as catalysts in the ether cleavage reaction. Bi (OTf)₃ and BiCl₃ react in catalytic quantity to cleaved the tertiobutyl–oxygen bound of the ethers 1, 3, 5.

The stereochemistry of the ring opening of (R,S) or (R,R)-4,5-dimethyl-2,2,2-triphenyl-1,3,2λ⁵-dioxaphospholanes (prepared by reaction of (R,S) or (R,R)-butane-2,3-diol with dibromotriphenylphosphorane) by aniline or thiophenol was investigated. The reaction affords stereoselectively the corresponding β-anilino- or β-phenylthioalcohols with a nearly complete inversion of stereochemistry at the stereogenic reaction centre.

The synthetic utility of 1,1,2,2-tetraphenyldisilane as a new, environmentally benign radical mediator is discussed for the reduction, cyclization, reductive addition to olefins, and alkylation of heteroaromatic bases.