Pierre Maroni

Le vibrateur SO dans les oxo-2 dioxathiannes-1,3,2: dédoublement de bandes par résonance de Fermi et utilisation possible en analyse conformationnelle

Abstract Forty-seven alkyl-, chloro- or nitro- cyclic sulfites in anancomeric conformation are examined in different solvents and, some at variable temperature through the SO region. Most of them show a doublet SO adsorption assigned to Fermi resonance by the method of solvent variation; this splitting does not arise from the intramolecular association only detected in less substituted molecules with non polar solvents. νSO frequencies are thus deduced and classified in three well localized types according to the three possible orientations of the SO group on a six membered cycle. Bellamy diagrams from eleven compounds indicate that the solvent effect on these frequencies is largely structure dependent. Finally, the integrated molar absorption coefficient of the νSO bands is found nearly constant and independent of the SO orientation.

Deplacement chimique en RMN 13C du carbone nucleophile d'un enolate et regioselective d'addition aux enones.

Abstract The ratio 1–2/1–4 addition of dimethyl-2,2 pentanone-3 enolates in Et 2 O to chalcone may be correlated to the chemical shift of the nucleophilic center in the enolate. Changes in associative states can be used to inverse the regioselectivity.

Structure o-metallee de lithiocycloalcanecarboxylates de t-butyle

Abstract Lithioesters obtained from (i-Pr)2NLi and cycloalkanecarboxylates at low temperature have been examined by 13C NMR and IR spectroscopy. The chemical shift values suggest an enolate nature of the derivatives even for the most angularly strained lithiocyclopropane carboxylate t-BuO(LiO)C= CCH 2 C H2. Comparison of ν(C=C) values of the metalated compounds and the corresponding methylenecycloalkanes is also in agreement with O-metalated structures in t-BuO(LiO)C= C(CH 2 ) n C H2 (n = 1−5).

Mise en evidence par rmn 13C et Ir d'enolates mixtes formes par reaction d'echange entre enolates lithiens et sels de metaux divalents

Abstract Mixed enolates (RO)2LiMgBr 4 and (RO)2LiZnBr 5 are obtained by addition of MgBr2 or ZnBr2 to the lithium enolate of 2,2-diMe pentanone-3 . The mixed magnesium enolate 4 is further transformed to ROMgBr with an additional equivalent of MgBr2 while 5 is unchanged by additional ZnBr2. The same mixed species are observed in the direct addition of preformed enolates.

Etude par RMN 13C Et 199Hg de composes oxobromo- et dioxomercuriques

Abstract Organomercuric compounds of the general formula and [RCOCH(R′)] 2 Hg, obtained from three ketones, 2,2-dimethyl 3-pentanone, 1-mesityl 1-propanone and 1-mesityl 1-ethanone, have been studied by 13 C and 199 Hg NMR techniques. Coupling constants J (CHg) and J (HgH) are consistent with C-metalated species; in each case the values of δ(C(2)) and J (C(2)H) observed are higher than expected for purely sp 3 carbon. The contribution of O-metalated species and hyperconjugative effects are discussed. For two dioxomercuric compounds (R′  Me, R  t-Bu, mesityl) the existence of diastereoisomers is suggested from 199 Hg NMR data.

Conformational analysis of cyclic sulphites. 2-oxo 1,3,2-dioxathiane-4-spiro-4-tert-butyl-cyclohexanes

Abstract Three series of 4-spirosulphites, a new class of cyclic sulphites, were synthesized and five couples of diastereoisomers isolated. Their structural analysis, using 1 H NMR coupling constants and SO stretching vibration as conformational probes, shows a large variety of ananchomeric chair forms and multicomponent equilibria for the cyclic sulphite moiety, the cyclohexane part of the molecule remaining in the chair form. Related to the occurrence of severe interactions involving the 5-methyl or 6- tert . butyl substituent, several twist forms were encountered, with 2,5-axis and isoclinal SO or 1,4-axis and axial or equatorial SO as a consequence of the weak free energy difference between chair and twist conformations in the cyclic sulphite series.

Une nouvelle classe d′inhibiteurs irréversibles les sulfinamoylesters précurseurs de sulfines

Abstract Tert -butyl N-aryl sulfinamoyl acetates are hydrolysed in aqueous basic media following a bimolecular elimination process, via an intermediate sulfine species. The use of sulfinamoyl compounds as irreversible inactivators for zinc-metallo-enzymes is emphasized.

Structure O- OU C-metallee des derives de la dimethyl-2,2 pentanone-3

Abstract Organometallic compounds obtained from 2,2-dimethyl-3-pentanone are studied by IR and 13 C NMR techniques. O - and C -metallated compounds may be differenciated by the latter technique. The solvent and metal effects on 13 C chemical shifts are discussed.

Sulphinamoylacetates as sulphine precursors. Mechanism of basic hydrolysis and scheme of irreversible inactivation of cinnamoyl alcohol dehydrogenase, an enzyme of the lignification process

t-Butyl N-arylsulphinamoylacetates are hydrolysed in aqueous basic media by an elimination mechanism. It takes place on the conjugate base of the substrate resulting from a fast deprotonation of the activated methylene group. This elimination is first order (E1 cB) for compounds where strong electron-withdrawing groups substitute the aromatic ring. For substitution by weaker electron-withdrawing or -donating groups, the elimination is second order, and needs the presence of general acid catalysis. For t-butyl N-(2-hydroxyphenyl)sulphinamoylisobutyrate where this mechanism of elimination is impossible, a BAc2 attack by hydroxide ion at the sulphur atom takes place. From these mechanisms and the results of complexation of zinc(II) cations by sulphinamoylacetates, a possible scheme for the irreversible inactivation of the title zinc metalloenzyme is proposed.

Zinc(II) complexes of sulfinamides—I. N-Phenyl 2-propane sulfinamide, t-butyl N-phenyl and t-butyl N-cyclohexyl sulfinamoyl acetates

Abstract The zinc(II) complexes of the title sulfinamoyl compounds L 2 ·ZnX 2 (X = Cl, Br) were prepared and studied by NMR and i.r. methods. All the complexes have a tetrahedral [O 2 X 2 ] coordination and NH . . X hydrogen bonding.