Bruno Rindone

Determination of toxic nitrophenols in the atmosphere by high-performance liquid chromatography

Abstract Seven HPLC columns were used for the optimization of the isocratic HPLC measurement of phenol, nitro- and dinitrophenols. A column constituted from 5 μm particles (100 A) of silica-based C 18 material was used for the analysis. Good separation of the analytes and their quantification in samples from the nitration of phenol in liquid and in gas phase in the laboratory was obtained. This approach allowed also to determine phenol in air samples.

Ozone oxidation of compounds resistant to biological degradation

Abstract The ozonation of a polyethoxylated nonyl phenol was carried out under different conditions of pH, reaction time and iron ion added. Analysis of the reaction products was performed using RP-HPLC, NP-HPLC and MS-FAB and the degradation of the polyethoxylated side chain to give a phenol was monitored. Several experiments of ozonation of different substituted phenols and widespread cinnamic acids are reported. Their degradation was monitored by u.v. measurements. Some mechanistic considerations are derived from these data.

A total synthesis of mycophenolic acid, some analogues and some biogenetic intermediates

Abstract Mycophenolic acid (28) has been obtained by a convergent synthesis starting from methyl 6-bromo-4-methylhex-4-enoate (13) and 5,7-dihydroxy-4-methylphthalide (24). For the total synthesis of 5,7-dihydroxy-4-methylphthalide, 1-carbethoxy-2,3-dimethylcyclohexa-4,6-dione (14) was aromatized and transformed into 4,6-dimethoxy-2,3-dimethylbenzamide. The photolysis of the corresponding N-chloroamide and subsequent hydrolysis gave 5,7-dimethoxy-4-methylphthalide which was hydrolysed to 5,7-dihydroxy-4-methylphthalide (24). The bromoester (13) was obtained starting from geraniol. Condensation between 13 and 24 with silver oxide in dioxane afforded the methyl ester of nor-O-methyl mycophenolic acid. Selective methylation and hydrolysis furnished mycophenolic acid.

Asymmetric biomimetic oxidations of phenols: the mechanism of the diastereo- and enantioselective synthesis of dehydrodiconiferyl ferulate (DDF) and dehydrodiconiferyl alcohol (DDA)

Abstract Stereoselective bimolecular radical coupling of enantiopure phenylpropenoidic phenols are described, starting from enantiopure amidic derivatives of ferulic acid. The latter were prepared from ferulic acid by reaction with (S)-alanine or Oppolzer camphor sultam. The oxidation step was performed both enzymatically (HRP/H2O2) and chemically (Ag2O). The observed enantioselectivity in the oxidation step encompasses the range 65–84% and is consistent with the conformational analysis of the quinone methide intermediates at the PM3 level.

The fate of triazine pesticides in River Po water

A group of triazine herbicides has been monitored in river Po water over a period of three years. The N-deethylated metabolite of atrazine was also found. Laboratory tests of biodcgradation of triazine performed with River Po water as cultural medium did not show any significant triazine degradation, leading to the conclusion that triazine metabolites derive from de.~-adation in soil. The chemical reactivity of triazines toward oxidants was also tested in laboratory with lead(IV) acetate, cerium(IV) ammonium nitrate and ozone. A chemical degradation pathway for triazines is suggested.

Acyclic and cyclic urea formation via the cobalt-catalysed oxidative carbonylation of aromatic primary amines

Abstract The N,N-bis(salicylidene)ethylenediaminocobalt(II)-catalysed oxidative carbonylation of aromatic primary amines in methanol gives ureas in good yields, with small amounts of carbamates and azo derivatives. Ortho-substituted aromatic amines also give cyclic ureas via a metal-induced oxidative carbonylation-cyclisation pathway.

ENANTIOSELECTIVE SYNTHESIS OF A BENZOFURANIC NEOLIGNAN BY OXIDATIVE COUPLING

Abstract The first stereoselective free radical coupling of a phenylpropenoidic phenolic compound is reported. The oxidation of a chiral ferulic acid amide to give dimeric benzofuranic neolignan is performed enzymatically using horseradish peroxidase as the catalyst. Enantiomeric excess in a biologically active compound with phenylcoumaran skeleton (β-5 dimer) is thus obtained.

The bis(salicylaldehyde)ethylenediimine cobalt(II)-catalysed oxidative carbonylation of primary and secondary amines

Abstract Anilines are oxidized to azobenzenes in methanol or methylene chloride solution using dioxygen as the oxidant and bis(salicylaldehyde)ethylenediimine cobalt(II) (CoIIsalen) as catalyst. In the presence of carbon monoxide, isocyanates, urethanes and ureas are also obtained. The latter two are the only reaction products when the aliphatic amine 1-adamantylamine is used as a substrate. Increasing the pressures of dioxygen and carbon monoxide significantly improves reaction yields. Ortho-aminophenol give the corresponding azo derivative and an oxazolone. Aromatic secondary amines give secondary formamides in low yields.

Synthesis of carbazole by Ru3(CO)12-catalyzed reductive carbonylation of 2-nitrobiphenyl: the crystal and molecular structure of Ru3(μ3-NC6H4-o-C6H5)2(CO)9

Abstract The Ru 3 (CO) 12 -catalyzed reductive carbonylation of 2-nitrobiphenyl 1 in acetonitrile gives carbazole 2 and 2-aminobiphenyl 3 . Compound 3 is the major reaction product in tetrahydrofuran, toluene, toluene-methanol, thiophene and cis -cyclooctene. Some products deriving from intermolecular insertion into the solvent are also found with acetonitrile, thiophene and cis -cyclooctene. By reaction of 2-nitrosobiphenyl 7 with Ru 3 (CO) 12 , the nitrene complex Ru 3 (μ 3 -NC 6 H 4 - o -C 6 H 5 ) 2 (CO) 9 11 has been isolated and its crystal structure has been determined. Compound 11 is orthorhombic, space group P2 1 2 1 2 1 with a = 11.160(4), b = 11.472(2), c = 25.478(6) A, Z = 4, R = 0.019, R w = 0.028, for 3161 independent reflections with I >3σ( I ). The ortho -substituent phenyl ring of the nitrene ligands in compound 11 is free to rotate around the CC bond and thus can assume the proper arrangement to allow insertion of nitrogen into the aromatic CH bond to give carbazole 2 . This possibility has been confirmed by treating 11 with CO (50 bar) at 220°C to obtain 2 and Ru 3 (CO) 12 .

Substituent effects in the cobalt-catalyzed oxidative carbonylation of aromatic amines

Abstract The N,N-bis(salicylidene)ethylenediaminocobalt(II)-catalyzed oxidative carbonylation of ortho-, meta- and para-substituted aromatic primary amines in methanol gives ureas, isocyanates, carbamates, azoderivatives. The conversion is correlated for six substrates with Hammett σ giving a ϱ = −0.5. This suggests the electrophilic attack of carbon monoxide at a nitrogen anion complexed to cobalt in the transition state. Force field calculations show that octahedral trans-diaminocobalt(III)salen intermediates have stability very similar to that of the corresponding cis derivatives. These latter are suggested to be intermediates in the formation of ureas. Steric effects in an unknown transition state may explain the fact that high yields in ureas are obtained only using para-substituted anilines as starting materials.