D. Misiti

Gold(III) catalyzed oxidation of sulfides to sulfoxides by nitric acid under phase-transfer conditions: a new synthesis of sulfoxides

Abstract Gold(III) halides catalyze the oxidation of sulfides to sulfoxides in a phase-transfer process. The organic sulfides, dissolved in nitromethane, are treated with (Bu4N+AuCl4−) in catalytic amount and aqueous nitric acid which acts as oxidant. The oxidation of the thio-group is selective and can be carried out also in the presence of other oxidizable groups, such as vinyl, tertiary amino, hydroxy, diol etc, which are left unchanged. Moreover in the case of asymmetric disulfides the reaction is regiospecific leading to the formation of a single monosulfoxide.

Synthesis of dimethyl acetals. diethyl acetals. and cyclic acetals catalyzed by aminopropylated silica gel hydrochloride (APSG-HCL)

Abstract The aminopropylated Silica-Gel hydrochloride (APSG.HCl) proved to be an efficient catalyst for the rapid conversion of carbonyl compounds in the corresponding acetals with high yields and in mild and selective conditions. In addition to the obvious advantages offered by heterogeneous catalysis, the present method results very useful when the presence of a weakly-acidic function chemically bonded on the catalyst surface (alkyl ammonium salt). is necessary (compounds which contains functions unstable in acidic media).

The palladium-catalysed conjugate addition type reaction of arylmercury compounds with α,β-unsaturated ketones in a two-phase system

Abstract Pd-catalysed reaction of arylmercury compounds with α,β-enones in an acidic two-phase system provides a mild and selective way to β-aryl ketones. The present conjugate addition type reaction may accommodate a wide variety of functional groups. Thus, aryl units containing electron-donating and electron-withdrawing substituents such as -Me, -Cl, -CHO, -COMe, -COOMe, -COOH, -OH, -OMe, -NHCOMe and -NO2 were successfully transferred to the β C atom of benzalacetone. A number of α,β-enones were also treated with 3-formylphenyl mercury chloride to give the corresponding β-(3-formylphenyl) derivatives. The main limitation seems to arise from steric hindrance in the starting α,β-enonic system. Substituents in the aryl moiety of the organomercury compounds were found to affect the transmetalation step in the direction expected for a rate determining σ-complex formation.

Oxidation of n-alkyl-n'-tosylhydrazines to hydroperoxides

Abstract N-Alky-N-tosylhydrazines upon treatment with H 2 O 2 and Na 2 O 2 give with high yields the corresponding aliphatic hydroperoxides. A discussion on the possible reaction mechanism which involves the formation of an “ion pair” intermediate, is reported. The reaction of tosylhydrazones carried out under simular conditions to give dihydroperoxides and other compounds is also described.

Selective and regiospecific oxidation of dithiaalkanes in a gold(III) catalyzed phase-transfer process

Abstract The oxidation of dithiaalkanes has been carried on in a gold(III) catalyzed phase-transfer process. Using a higher concentration of catalyst and oxidant (procedure A ) the bis(benzylthio)alkanes Bz-S-(CH2)-S-Bz (Bz = benzyl) were ·Oxidized to the corresponding monosulfoxide when n = 1 and to disulfoxide [bis(benzylsulfinyl)alkanes] when n = 2, 3, 4, 5, and 8. In more diluite conditions (procedure B ) high yields of monosulfoxides were obtained also in the case of n = ·2 and 3 while the selectivity decreased for n = 4, 5, and 8. The oxidation of asymmetric dithiaalkanes, R-S-(CH2)3-S-R (RR = BzPh, BzCy, CyPh; Ph = phenyl, Cy = cyclohexyl), under experimental conditions B was regiospecific leading either to the formation of only one type of monosulfoxide (RR = BzPh) or to the formation of both types of monosulfoxides but in different yield (RR = BzCy and CyPh); in all cases the alkylic and less hindered sulfur atom was oxidized in preference.

Hindered rotation about the metal-nitrogen bond in trans-dichlorodihydrazonepalladium(II) complexes and X-ray crystal structure of trans-bis(acetone methylphenylhydrazone)dichloropalladium(II)

The complexes trans-[PdCl2L2][L = Me2CN–NMePh (L1); Et2CN–NMePh (L2); PrnMeCN–NMePh (L3); MeHCN–NMePh (L4); Me2CN–NMe2(L5); or MeHCN–NMe2(L6)] have been prepared by reaction of the hydrazone ligands with [PdCl2(NCPh)2]. The crystal and molecular structure of trans-[PdCl2(Me2CN–NMePh)2] has been determined from three-dimensional X-ray data. The complex crystallizes in the monoclinic space group P21/n with two molecules in a cell of dimensions a= 18.83(3), b= 7.53(2), and c= 7.76(2)A, β= 89.1(5)°. The palladium atom lies at a centre of symmetry; consequently the four ligating atoms, i.e. the two chloride ions and the two imino-nitrogens of the hydrazones, are located rigorously in a plane passing through the central metal. The co-ordination plane is nearly perpendicular to the plane containing the non-hydrogen atoms of the hydrazone skeleton Me2CN–N. Significant bond distances are Pd–Cl 2.298(4) and Pd–N 2.047(2)A. Another isomeric structure of this complex can be obtained by 180° rotation about the Pd–N bond of one of the two hydrazone ligands. This isomer is not centrosymmetric but contains a plane of symmetry which is perpendicular to the co-ordination plane and passes through the Cl–Pd–Cl axis. Both these isomers exist in equilibrium in solution for all the prepared complexes. Values of free energies of activation for the interconversion process have been obtained from temperatures of coalescence of the n.m.r. signals; they vary from 58 to 89 kJ mol–1 with the nature of the ligand substituents. In particular, complexes of hydrazones derived from aldehydes (L4 and L6) have ΔG‡ 10–14 kJ mol–1 lower than those of analogous hydrazones derived from ketones (L1–L3 and L5); complexes of hydrazones derived from methylphenylhydrazine (L1–L4) have ΔG‡ 17–21 kJ mol–1 lower than those of analogous hydrazones derived from dimethylhydrazine (L5 and L6).

Reduction of N-acyl,N′-tosylhydrazines with diborane. A simple, convenient procedure for the conversion of the carboxylic to the methyl group

Abstract Aliphatic tosylhydrazides upon treatment with diborane followed by alkaline hydrolysis yield aliphatic hydrocarbons. Aromatic hydrocarbons are produced when aromatic tosylhydrazides undergo heating in presence of diborane and are subsequently oxidated by KIO4. A discussion on the structures of intermediate products is reported.

The behaviour of trans-dihalogenobis(hydrazone)palladium(II) complexes: rotational isomerism or non-equivalence of the two ligands within the same molecule?

A detailed 1H n.m.r. analysis of a series of trans-dihalogenobis(hydrazone)palladium(II) complexes has been made in order to demonstrate unequivocally the presence of two rotational isomers differing in the mutual orientation of the co-ordinated ligands.