C. Berrier

Nitronate anions as precursors of hydroxynitrilium ion equivalents in electrophilic aromatic substitution - a novel route to oximes

Abstract Nitronate salts RCHNO 2 Na react with aromatics ArH in acidic conditions to yield the corresponding oximes ArCRNOH via protonated nitronic acids.

Fluorination in superacids: a novel access to biologically active compounds

Abstract In HF-SbF 5 , reaction of various alkaloids with NBS, NCS, H 2 O 2 yields fluoroderivatives: anti-addition is observed at the C6C7 double bond with tabersonine, but a more complex reaction is operative with vindoline, leading to 7-substituted (Br, Cl, OH)-20-fluoro derivatives. A completely different reaction pathway is observed with bis indole alkaloids (vinblastine, anhydrovinblastine, vinorelbine) in HF-SbF 5 . In the presence of NBS (or better of CCl 4 or CHCl 3 ), 20′,20′-difluoroderivatives are obtained. Vinflunine (20′,20′-difluoro-3′,4′-dihydrovinorelbine) has been selected for its promising antitumor activity.

Synthesis of fluorohydrins and of bromofluoroderivatives by anti addition on the 14,15 double bond of tabersonine in superacids

Abstract Reaction of tabersonine 1a with H2O2 in HF-SbF5 yields fluorohydrins 2(22%), 3(36%) and 4(21%). In similar conditions 1a reacts with Br2 (0.6 equivalent) to give compounds 7(27%), 8(14%) ard 9(41%). These results imply addition of the electrophile H3O2+ and Br2 (“OH+” and “Br+” equivalent respectively) on the α or β face of the C-14-C-15 double bond to yield onium ions 12α or 12 β. Trapping of these ions by a fluoride ion accounts for the stereospecific formation of the anti addition products. P]Assignment of the chemical shift of every carbon has been carried out in the new compounds using, if necessary, COSY 13C-1H to remove any ambiguity.

Direct bromination or hydroxylation at C-11 in vincadifformine and tabersonine derivatives in superacids

Abstract In HF-SbF5, vincadifformine 1b reacts with H2O2 to yield a mixture (60%) of hydroxyderivatives 1c and 1d. 2,16-Dihydrovincadifformine 2a is more selectively hydroxylated at C-11 to give 2b (40%); in a similar reaction, 2d yields 2e (37%). Reaction of 2a with Br2 in HF-SbF5 gives regioselectively compound 2c (80%).

Hydroxylation of indolines and indoles by hydrogen peroxide in superacids

Abstract In SbF 5 -HF, indolines and indoles are hydroxylated on the aromatic ring, protonated hydrogen peroxide H 3 O 2 + reacting on the protonated substrates.

Regio- et stéréo-réactivité d'une lactone dissymétrique: détermination de structure par effets nucléaires Overhauser et modélisation moléculaire

Abstract Lactone I is an important intermediate in the synthesis of compounds with therapeutic properties. In order to prepare new derivatives, reactivity of I has been studied. Cis and trans conformations of both 2,3-diphenyl-1-oxabicyclo [3,1,0] hexanes VIIIa and VIIIb were assigned by 1 H N.M.R spectroscopy using NOE DIFF experiments, and molecular modelling.

Synthese totale de steroides a cycle c aromatique

Abstract The ring-C aromatic analogue 4 of 4-androstene 3,17-dione and its 11 hydroxylated (methoxylated) derivatives 20a(b) were prepared by a practical synthetic route. The key steps of the sequence are achieved in superacid: the cyclisation of diarylethane 5a to phenanthrenone 17, and the hydroxylation by hydrogen peroxide of ketone 4 to phenol 20a.

Cyclisatioh de diarylalcanes en milieu superacide : synthese de cetones tricycliques a methyle angulaire et mecanisme de leur isomerisation

Abstract Cyclisation of readily available diary1-1,2 ethanes 1→4 proceeds in SbF5,-HF at 0°C to yield tricyclic phenanthrenones 5 , 6 , 7 and 11 bearing an angular methyl group. This process implies the electrophilic attack of the more basic aromatic ring, reacting through its diprotonated form (on the oxygen and the meta carbon atom) on the second aromatic ring. Isomerization of these primary products may be observed to give ketones 8 , 9 , 10 from 3 and 12 from 4 ) and it has been demonstrated by the use of specifically deuterated 3d that it involves stereospecific 1,2 hydride (or deuteride) shifts, without exchange.

Transposition d'un Δ24 steroide: Application a la synthese d'un sterol marin 24-methyle

Abstract Desmosterylacetate reacts with Tl (III) acetate to give a rearranged ketone, 3β-acetoxy-27-nor-24ϵ-methyl cholest-5-en-25-one as by product. This compound is converted into 25-hydroxy-24ϵ-methyl-cholesterol, a marine sterol.

A novel efficient route to hexahydrodibenzofuran derivatives

Abstract Synthesis of 2 and 4-aryl cyclohexenones and of hexahydrodibenzofuran derivatives is described. In anhydrous hydrogen fluoride at 0°C, 4-hydroxy-4 methylcyclohex-2 en-1 one 2 reacted to yield ketone 7 (43%). Reaction of ketone 2 with parabromophenol 13b in HF gave ketone 6 (40%) at −20°C and ketone 6 (35%) and 7 (13%) at 0°C. Under similar conditions ketone 2 reacted with phenol 3a to yield 2 and 4 arylated ketones 4a (4%), 5 (a+b) (25%) and 9a (5%).