A. Laporterie

SURPRISING CATALYTIC ACTIVITY OF BISMUTH (III) TRIFLATE IN THE FRIEDEL-CRAFTS ACYLATION REACTION

Bismuth tris-trifluoromethanesulfonate (Bi(OTf)3) was found to be a novel catalyst for the Friedel-Crafts acylation. The reactions of activated or deactivated benzenes such as fluorobenzene proceeded in high yields in the presence of a catalytic amount of Bi(OTf)3. This catalyst is water stable and its catalytic activity is much higher than the one of the other metallic triflates M(OTf)3 previously reported (M = Al, Ga, Ln or Sc).

Ene-reactions en series organosiliciee et germaniee

Abstract Ene reactions involving enes and enophiles of silicon and germanium have been investigated. Organometallic δ-ethylenic compounds were synthesized and an allylic group converted into a vinylic one , to obtain 1-sila- or 1-germacyclopent-2-enes.

Synthesis of 3-methylene-1,1-dichlorosilacyclobutane and 1,1-dichlorosilacyclopent-3-ene

Abstract : Silacyclobutanes have played an important role in the development of modern silicon chemistry. For example, silacyclobutanes serve as precursors to carbon-silicon double bonded intermediates silenes as well as to pentacoordinate silicon anions in the gas phase. Silacyclobutanes also undergo facile ring opening polymerization. Despite the importance of this ring system surprisingly few functionalized silacyclobutanes and silacyclobutenes have been prepared. Similarly, there is considerable interest in 1-silacyclo-pent-3-enes due to their facile conversion into other functionalized silicon heterocycles as well as due to their ability to undergo anionic ring opening polymerization. These compounds have usually been prepared by reaction of a 1,3-diene with a dihalosilane under dissolving metal reduction conditions. (jes)

BiCl3-catalyzed Mukaiyama-aldol and carbonyl-ene reactions

Abstract The H-ene pathway has not been detected for the bismuth(III) chloride-catalyzed Mukaiyama-aldol reaction involving silyl enol ethers and aldehydes. The silatropic ene-like process is the only mechanism observed, even with the weakly reactive 1-(trimethylsilyloxy) cyclohexene. However, trimerization of an aliphatic aldehyde can occur.

Chimie des metalloles du groupe IV. Synthese de methylsiloles par thermolyse d'esters de silacyclopentene-4 ols-3 et complexes η3-fer tricarbonyles

Thermolysis of esters of silacyclopent-4-ene-3-ols Me2SiCHCRCR′(X)CH2 (R,R′ = H or Me; X = OC(O)NHPh, OC(S)SMe) leads to 1,1-dimethylsilole (1), 1,1,3-trimethylsilole (2) or 1,1,3,4-tetramethylsilole (3). The thermally unstable S-methylxanthates decompose involving both competitive β-CH and β-CSi eliminations. With N-phenylcarbamates a regioselective CH elimination on an endocyclic carbon, leading to the expected siloles 1–3, is mainly observed. A one pot synthesis of 3, the first methylsilole stable as a monomer, from the corresponding alcohol (X = OH, R = R′ = Me) and phenyl isocyanate is described. 1,1,3,4-Tetramethylgermole (4) is similarly obtained. The relative stability of the methylsiloles, their ability to form Diels-Alder dimers and to isomerize into a transoid diene, is discussed. In this respect, the strong influence of C-methyl groups on the stabilization of the tetramethylsilole, as in the case of the 1,1,3,4-tetramethylphospholium ion, is made possible. The principal characteristics of NMR and mass spectra of methylsiloles 1–3 and those of their stable tricarbonyliron complexes are studied.

Synthese du dimethyl-1,1 silole

Abstract The first synthesis of a monomeric C-unsubstituted silole is described. Photo-oxygenation of 1,1-dimethyl-1-silacyclopent-3-ene leads to an allylic hydroperoxide with a shifted carobon—carbon double bond (ene reaction) which, upon treatment with a reducing agent (NaBH 4 ) gives 1,1-dimethyl-1-silacyclopent-4-ene-3-ol. Catalytic vacuum-flow dehydration of this alcohol gives monomeric 1,1-dimethylsilole, which is characterized by its PMR spectrum at room temperature and by its Diels—Alder adducts.

Ène-réactivité d'allylsilanes: Fonctionnalisation et régiochimie

Abstract The hydroperoxidation of various allylsilanes by singlet oxygen has been studied. The regioselectivity of this reaction compared to those of ethyl azodicarboxylate and 4-phenyl-1,2,4-triazoline-3,5-dione, is discussed. Mechanisms are considered in the general field of the ene reaction applied to allylic organometallic Group IVB compounds. The structures of the new products (alcohols, urazoles, hydrazines) have been determined, directly or after transformations, by NMR spectroscopy.

A convenient synthesis of 1,1,3,4-tetramethylsilole : A stable IVB-metallole

Abstract 1,1,3,4-tetramethyl-3-phenylcarbamoyl-1-silacyclopent-4-ene is found to undergo quantitative decomposition in refluxing CCl 4 to regiospecifically afford 1,1,3,4-tetramethylsilole which is remarkably stable toward dimerisation, and is easily converted into its iron carbonyl-diene complex.

Chimie des metalloles IV B . Action d'organolithiens sur les tetramethyl-1,1,3,4 silole ou germole

Abstract The reaction of RLi ( R=nBu,tBu,PhLi ) with 1,1,3,4-tetramethylsilole or germole in THF gives via a ligand exchange ( SN -Si or Ge ) the 1-R-1,3,4 trimethylmetalloles or the 1,1-di-R-3,4-dimethylmetalloles (A). Metalation of MMe groups is not observed but a partial (nBuLi,PhLi) or important (tBuli) isomerization of metalloles into the transoid exocyclic dienes (B) occurs.

Le dimethyl-1,1 germole

Abstract The first synthesis of an unsubstituted germole is described. Catalytic vacuum-flow dehydration (Al 2 O 3 , 300°C, 0.01 mmHg) of 1,1-dimethyl-1-germacyclopent-4-ene-3-ol gives monomeric 1,1-dimethylgermole, which is characterized by its PMR spectrum at room temperature and by its Diels—Alder adduct with maleic anhydride.