Ágnes Gömöry

Practice of fluorous biphase chemistry: convenient synthesis of novel fluorophilic ethers via a Mitsunobu reaction

Abstract The evolution of the term fluorous is addressed first, then a concise terminology is proposed, including fluorous partition coefficient, specific fluorophilicity and fluorousness. Some examples are shown for the design of higher generation fluorophilic molecules, involving Class I to Class III ponytails. Fluorophilic ethers of the structure of ArC(CF3)2O(CH2)m(CF2)nF (m=1, n=1, 7; m=3, n=8) are obtained in high yields, when 2-aryl-1,1,1,3,3,3-hexafluoro-propanols are reacted either with trifluoroethyl- and 1H,1H-perfluorooctyl triflates (NaH/DMF, Williamson ether synthesis) or with 3-perfluorooctyl-propanol (Ph3P/EtO2CNNCO2Et/PhCF3, Mitsunobu reaction), respectively. Fluorophilic phenol- and perfluoro-tert-butyl ethers can also be prepared effectively by the latter method. In case of higher homologues (n=7, 8) product isolation can be facilitated using fluorous extraction (C6F14/CH3OH). Specific fluorophilicity values of target molecules are estimated using a 2D method and compared with experimentally determined ones.

Convenient syntheses and characterization of fluorophilic perfluorooctyl-propyl amines and ab initio calculations of proton affinities of related model compounds

Abstract A convenient and effective method for the preparation of perfluorooctyl-propyl amines ([R f8 (CH 2 ) 3 ] n NH 3− n ( 1 – 3 ), n =1,2,3; R f8 (CH 2 ) 3 NHMe ( 4 ); [R f8 (CH 2 ) 3 ] 2 NMe ( 5 ); R f8 (CH 2 ) 3 NMe 2 ( 6 ); R f8 =F(CF 2 ) 8 ) via a step by step alkylation with R f8 (CH 2 ) 3 I is described. The fluorophilicity values of 1 – 6 were determined by GC and range from 0.79±0.07 ( 1 ) to 5.3±0.2 ( 3 ). Systematic ab initio calculations of proton affinities of model compounds ( 7a – j ) using Hartree–Fock and density functional theory imply that the inserted trimethylene spacer unit efficiently reduces the electron-withdrawing effect of the perfluorinated segment. All structures were verified by multinuclear one- and two-dimensional NMR experiments involving both homo- ( 19 F – 19 F ) and hetero-nuclear ( 1 H – 13 C , 1 H – 15 N , 19 F – 13 C ) correlations based on the GMQFCOPS and inverse 1 H and/or 19 F detected GHSQC, GHMQC sequences with broadband adiabatic 13 C -decoupling.

A study on the catalytic pathways of the hydroalkoxycarbonylation reaction of styrene

Abstract The catalytic pathways of the Pd(PPh 3 ) 2 Cl 2 /SnCl 2 -catalysed styrene hydroalkoxycarbonylation reaction have been elucidated. Using deuterium labelling, the different reaction products were detected by mass spectral analysis and the deuterium content and its distribution determined by 1 H-, 2 H- and 13 C-NMR methods. The great number of labelled species supports the assumption that the hydrido (Pd–H) route is the operating mechanism of this system. Alkyl–metal intermediates easily undergo β-hydride elimination. This process is reversible for both isomers even at low reaction temperature

Sensitivity of redox reactions of dyes to variations of conditions created in mass spectrometric experiments

Redox behaviour of four imidazophenazine dye derivatives under mass spectrometric conditions of matrix-assisted laser desorption/ionization (MALDI), laser desorption/ionization (LDI) from metal and graphite surface, electrospray, low temperature secondary ion mass spectrometry (LT SIMS) and fast atom bombardment (FAB) was studied and distinctions in the reduction-dependent spectral patterns were analyzed from the point of view of different quantities of protons and electrons available for reduction in different techniques. The reduction products [M + 2H](+*), [M + 3H](+) and M(-*), [M + H](-) were observed in the positive and negative ion modes, respectively, which permitted to suggest independent occurrence of reduction and protonation/deprotonation processes. LDI from graphite substrate was the only technique that allowed us to obtain abundant negative ions of all dye derivatives. The yield of field ionization (FI) or field desorption (FD) mechanism to ion formation under LDI from rough graphite surface has been addressed. The sensitivity of reduction of the dyes to variation of reduction-initiating agents confirms high redox activity of the dyes essential for their functioning in natural and artificial systems.

Mass spectrometric and MNDO study of electron impact induced fragmentation of some norbornane- and norbornene-condensed pyrimidinones and oxazinones

Abstract The main electron impact induced fragmentation processes of nine norbornane- or norbornene-condensed 2-aryl-1,3-pyrimidin-4(3H)-ones and six oxazinone analogues were established by means of mass spectrometry and MNDO calculations. The fragmentations involve the common and main process of selective and simple bond cleavage in the norbornane skeleton, followed by McLafferty H-rearrangement, and a competing and hidden retro Diels-Alder (RDA) reaction of the hetero ring. The norbornenes additionally undergo an RDA reaction directed by the CC double bond. The decomposition schemes deduced from mass spectrometric measurements were supported by the theoretical results. MNDO bond orders and charge densities calculated for neutral and ionized model molecules proved to be informative for the interpretation of the observed fragmentations. MNDO heats of formation for neutral and ionized products also indicate the high probability of the suggested main fragmentation processes.

Synthesis of steroid-ferrocene conjugates of steroidal 17-carboxamides via a palladium-catalyzed aminocarbonylation - Copper-catalyzed azide-alkyne cycloaddition reaction sequence

Steroids with the 17-iodo-16-ene functionality were converted to ferrocene labeled steroidal 17-carboxamides via a two step reaction sequence. The first step involved the palladium-catalyzed aminocarbonylation of the alkenyl iodides with prop-2-yn-1-amine as the nucleophile in the presence of the Pd(OAc)(2)/PPh(3) catalyst system. In the second step, the product N-(prop-2-ynyl)-carboxamides underwent a facile azide-alkyne cycloaddition with ferrocenyl azides in the presence of CuSO(4)/sodium ascorbate to produce the steroid-ferrocene conjugates. The new compounds were obtained in good yield and were characterized by (1)H and (13)C NMR, IR, MS and elemental analysis.

A new cyclization to fused pyrazoles tunable for pericyclic or pseudopericyclic route: an experimental and theoretical study.

2-Pyrazinyl (2) and 3-pyridazinylketone arylhydrazones (6) and their benzologues undergo a ring closure reaction to yield pyrazolo[3,4- b]pyrazines (4) and pyrazolo[4,3- c]pyridazines (7), respectively, in acceptable to good yields. The reaction was found to be accelerated by using acidic or basic conditions. Quantum chemical calculations suggest the key step of the mechanism to be a direct cyclization; analysis of aromaticity based on computed magnetic properties revealed its medium-dependent pericyclic or pseudopericyclic character. The cyclization reaction has also been extended for the synthesis of related ring systems ( 9, 12, 14).

Predicting primary mass spectrometric cleavages : a 'quasi-Koopmans' ab initio approach

Comparison of the bond order indices calculated for neutral molecules and for their ions obtained by removing one electron either from HOMO or from one of the near-to-HOMO occupied orbitals can be used to predict the primary bond cleavage processes taking place in an electron impact mass spectrometric experiment.

Direct study of unstable dimethylgermathione, Me2GeS, by vacuum pyrolysis-MS and low temperature matrix IR spectroscopy

Abstract Dimethylgermathione, Me2GeS (D1), has been studied by vacuum pyrolysis-MS and matrix isolation IR spectroscopy. The germathione D1 was generated in the gas phase by pyrolytic decomposition (730–900°C, 10−2 −10−3 Torr) of the trimer (Me2GeS)3 (D3) in a quartz pyrolyzer, coupled to the ionization chamber of mass spectrometer or to an optical helium cryostat, where pyrolysis products have been frozen at 12 K in an argon matrix. The ionization energies (IE) of D3, D1 and its cyclodimer (D2) have been determined from measurements of ionization efficiency curves in mass spectra of pyrolysis products of D3 and using the semilogplot tehcnique. The IE revealed for D1 (8.63±0.1 eV) practically coincided with that obtained earlier by PES, which proved the formation of monomeric D1 in the reaction. In the matrix IR spectra (Ar, 12 K) of pyrolysis products of D3 the bands 518, 574, 606, 765, 809, 850, 1231 and 1392 cm−1, disappearing simultaneously inw arming-up experimnts (to 35–40 K). These were ascribed to germathione D1. By comparison of experimental frequencies with the calculated values the band 518 cm−1 was assigned to GeS stretching vibration. The calculated geS bond force constant (4.08 mdyn/A) is a direct physical characteristic, giving strong evidence for considerable duoble bonding in dimethylgermathione.

Mass spectrometric evidences for the formation of unstable 1,1,3,3-tetramethyl-1,3-cyclodisiloxane in the gas phase

Abstract Mass spectrometry during the vacuum pyrolysis of either 3,3-dimethyl-6-oxa-3-silabicyclo[3.1.0]hexane ( 1 ) or its 1,5-dimethyl derivative ( 2 ), both of which are dimethyl silanone (D 1 ) precursors, indicated that 1,1,3,3-tetramethyl-1,3-cyclodi-siloxane (D 2 ) was present among the pyrolysis products in the gas phase. D 2 is unstable under normal conditions.