Maria Concetta Natoli

Melatonin: structural characterization of its non-enzymatic mono-oxygenate metabolite

Abstract: Oxidation of melatonin by Fenton reagents as well as with hypochlorous acid or oxoferryl hemoglobin has been investigated. Analysis of products by low resolution/mass spectra (MS), high resolution/MS, 1H‐nuclear magnetic resonance (NMR), 13C‐NMR, correlated spectroscopy (COSY) and heterocorrelated spectroscopy (HETCOR) 2D NMR reveals the formation of a single mono‐oxygenated product under all conditions and unequivocally assigns the N‐[2‐(5‐methoxy‐2‐oxo‐2,3‐dihydro‐1H‐indol‐3‐yl)‐ethyl]‐acetamide structure, which had not been previously considered.

A new general fragmentation reaction in mass spectrometry: The hydrogen-carbon, carbon-carbon double rearrangement of 2 heteroalkyl substituted diphenylmethyl cations

Diphenylmethyl cations formed by benzylic cleavage of the molecular ions of ortho heteroalkyl substituted 1,1-diphenylalkanes undergo the double rearrangement process (H to C followed by C to C) previously reported for ortho-methoxy derivatives. Hence the formation of substituted benzyl (or tropylium) ions allowing this double rearrangement process constitutes an interesting type of fragmentation reaction characteristic for 1,1-diphenylalkanes bearing ortho substituents (OMe, OEt, OiPr, SMe, NHMe, NMe2) which are able to transfer a hydride to the charged benzyl carbon of diphenylmethyl cations formed by benzylic cleavage of the molecular ion.

Studies in organic mass spectrometry. Part 25. Benzyl ion formation in chemical ionisation (methane or isobutane) of some ortho‐alkylhetero‐substituted diphenylcarbinols

The behaviour of some ortho-alkylhetero-substituted diphenylcarbinols, including deuterium labelled derivatives, under chemical ionisation (methane or isobutane) conditions has been investigated. It has been determined that ortho-alkylhetero diphenylmethyl cations formed by water elimination from the protonated molecule undergo consecutive rearrangements which afford benzyl (or tropylium) ions previously observed for ortho-substituted diphenylcarbenium ions generated by electron ionisation. This reaction also occurs under low-energy collision conditions. Copyright 2000 John Wiley & Sons, Ltd.

Studies in Organic Mass Spectrometry; Part 26. Unimolecular Decomposition of Ortho-Methoxy-Substituted Diphenylmethyl Cations

A double rearrangement (hydrogen migration followed by carbon–carbon displacement) constitutes the main fragmentation process of the 2-methoxydiphenylmethyl cations formed by benzylic cleavage of the molecular ion of ortho-methoxy-substituted 1,1-diphenylalkanes with a wide range of internal energy. This has been demonstrated by recording mass analysed ion kinetic energy (MIKE) spectra, calculation of approximate activation energies (obtained by appearance energy difference) and calculation of a degrees-of-freedom effect. A geometry of the transition state, which accounts for the observed substituent effects, is proposed.

Kinetic study of base‐promoted elimination reactions of some 1,1,1‐trihalo‐2,2‐bis(dimethoxyphenyl)ethanes in alcoholic solutions

The base–promoted elimination reactions of 1,1,1-trichloro-2,2-bis(dimethoxyphenyl)ethanes were investigated. The bis(3,4-dimethoxyphenyl)ethane was found to be more reactive than the bis(2,5-dimethoxyphenyl)ethane and the latter more reactive than the bis(2,4-dimethoxyphenyl)ethane. Kinetic data relative to 1,1,1-trihalo(chloro or bromo)-2,2-bis(3,4-dimethoxyphenyl)ethanes show that the tribromo reacts faster than trichloro derivative and that the reactions are general-base promoted with Bronsted β values of about 0.6. A kinetic isotope effect, with kH/kD ratio ranging from 3.5 to 5.7, for the base-promoted elimination reaction of 1,1,1-trichloro-2,2-bis(3,4-dimethoxyphenyl)ethane was found. Tunneling occurs for methoxide and ethoxide ion-promoted eliminations. Activation parameters for alkoxy-promoted elimination show a similar trend for chloride and bromide derivatives. The data collected seem to confirm that there is contiguity between E1cBirr and E2 mechanisms.

Hydrogencarbon, carboncarbon double rearrangement induced by proximity effect in alkyldiaryl- and triarylmethyl cations

The double rearrangement process affording benzyl (or tropylium) ions, which constitutes the main fragmentation reaction for 2-alkylheterodiphenylmethyl cations, is also observed in the presence of a further substituent (alkyl or aryl) linked to the benzylic carbon. This process is still responsible for important peaks in the mass spectra.

Synthesis of Symmetrical 1,4-Diarylphthalazines

Abstract It is well known that 1, 4-diarylphthalazines are prepared by condensation of the appropriate ortho-diaroylbenzenes with hydrazine hydrate.1 As ortho-diaroylbenzenes can be obtained by oxidation of ortho-dibenzylbenzenes, a rapid method is proposed to obtain the ortho-dibenzylbenzenes (Ia) and (Ib) by reaction of the highly reactive2 veratrol with para-chloro- or ortho-chlorobenzyl alcohol in sulfuric acid. The products obtained gave by oxidation the ortho-diaroylbenzenes (IIa) and (IIb), which were transformed into the 1,4-diarylphthalazines (IVa) and (IVb) by treatment with hydrazine hydrate.

9,10-Dihydroanthracene and 6,11-Dihydroaceanthrene Derivatives

Abstract In the field of oxido-reductive transformations of 9, 10-halogenomethyl-9,10-dihydroanthracenes into anthracenes1, the synthesis of 2,3,6,7-tetramethoxy-9,9-dimethyl-10-trichloromethyl-9,10-dihydroanthracene (IIa) from 3, 4,3′,4′-tetramethoxy-diphenyl-dimethylmethane (I) and chloral in conc. H2SO4 medium has been attempted. Such a reaction however gave 2,3,6,7-tetramethoxy-9,10-bis (trichloromethyl)-9,10-dihydroanthracene and an indenic compound whose formation was ascribed to an initial cleavage of (I)2: no trace of the expected product (IIa) was detected.