TY - BOOK A1 - Pihlaja, Kalevi A1 - Kleinpeter, Erich T1 - 13C NMR chemical shifts in structural and stereochemical analysis T3 - Methods in stereochemical analysis Y1 - 1994 PB - VCH CY - New York ER - TY - JOUR A1 - Mäki, E. A1 - Pihlaja, Kalevi A1 - Kleinpeter, Erich A1 - Hartmann, Jürgen A1 - Schroth, W. T1 - Electron impact ionization mass spectrometry of some 4,9-Dihetro-(X,X)-cyclodeca-1,6-dienes : mono- and dibenzo analogues Y1 - 1994 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Pihlaja, Kalevi T1 - Functions containing a thiocarbonyl group and at least one halogen, also at least one chalcogen and no halogen Y1 - 1995 ER - TY - JOUR A1 - Pihlaja, Kalevi A1 - Lehmann, S. A1 - Schroth, W. A1 - Gäber, M. A1 - Kleinpeter, Erich T1 - Electron impact induced fragmentation of dibenzo crown ethers Y1 - 1996 ER - TY - JOUR A1 - Kleinpeter, Erich A1 - Heydenreich, Matthias A1 - Woller, Jochen A1 - Wolf, Gunter A1 - Koch, Andreas A1 - Kempter, Gerhard A1 - Pihlaja, Kalevi T1 - Configuration and stereodynamics of exo/endoisomeric push-pull alkenes of pentadiene structure Y1 - 1998 ER - TY - JOUR A1 - Reiche, K. B. A1 - Starke, Ines A1 - Kleinpeter, Erich A1 - Holdt, Hans-Jürgen A1 - Pihlaja, Kalevi A1 - Oksaman, P. A1 - Ovcharenko, V. V. T1 - Fragmentation of imine-type meta-bridged bis(benzo crown ether)s under electron impact Y1 - 1999 ER - TY - JOUR A1 - Tahtinen, Petri A1 - Bagno, Alessandro A1 - Koch, Andreas A1 - Pihlaja, Kalevi T1 - Conformational analysis of saturated trans-fused 1,3,2-benzoxazaphosphinine 2-oxides - DFT calculation of NMR J(PH) coupling constants N2 - The (3)J(P,H) and (4)J(P,H) spin-spin coupling constants of a selected test set of organophosphorus compounds, calculated by density functional theory (DFT) methods, were found to correlate well with the experimentally measured coupling constants. The contribution of the spin-dipole (SD) term to the coupling constants was found to be negligible, and the diamagnetic and paramagnetic spin-orbit (DSO and PSO) terms cancelled each other, as in the case of J(H,H). Calculation solely of the Fermi contact (FC) term was found to be sufficient to provide good estimates of the coupling constants. In the second part of the work, the conformational equilibria and coupling constants in 2-bis(2- chloroethyl)amino-trans-octahydro-2H-1,3,2-benzoxazaphosphinine 2-oxide and its 3-methyl derivative were studied. DFT methods failed in predicting the relative stabilities of the conformations but yielded good geometries and coupling constants. Optimization of the conformations at the Moller-Plesset second-order perturbation theory (MP2) level resulted in energy differences compatible with previous experimental observations. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) Y1 - 2004 SN - 1434-193X ER - TY - JOUR A1 - Starke, I. A1 - Sarodnick, Gerhard A1 - Ovcharenko, V. V. A1 - Pihlaja, Kalevi A1 - Kleinpeter, Erich T1 - Quinoxalines : Part 13: Synthesis and mass spectrometric study of aryloxymethylquinoxalines and benzo[b]furylquinoxalines N2 - A series of new aryloxymethylquinoxalines, benzo[b]- and naphtho[2,1-b] fury] quinoxalines, possessing potential biological activity, was prepared, characterized by IR and NMR spectroscopy and their electron ionization (EI) mass spectra studied in detail. The aryloxymethylquinoxalines were obtained by reacting halogenomethylquinoxalines with bifunctional O-nucleophiles. The benzo[b]furylquinoxalines and naphtho[2, I -b]furylquinoxalines were prepared via two routes, which differed in the order of the two cyclization steps involved in the syntheses. The composition of the ions obtained by El mass spectrometry were determined by accurate mass measurements and the fragmentation pathways clarified by B/E linked scans and collision induced dissociation. The mass spectrometric behaviour of the compounds studied as to the possible loss of OH' radicals proved to be very characteristic. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 SN - 0040-4020 ER - TY - JOUR A1 - Neuvonen, Kari A1 - Fulop, Ferenc A1 - Neuvonen, Helmi A1 - Koch, Andreas A1 - Kleinpeter, Erich A1 - Pihlaja, Kalevi T1 - Propagation of polar substituent effects in 1-(substituted phenyl)-6,7-dimethoxy-3,4-dihydro- and -1,2,3,4- tetrahydroisoquinolines as explained by resonance polarization concept N2 - Propagation of inductive and resonance effects of phenyl substituents within 1-(substituted phenyl)-6,7- dimethoxy-3,4-dihydro- and -1,2,3,4-tetrahydroisoquinolines were studied with the aid of C-13 and N-15 NMR chemical shifts and ab initio calculations. The substituent-induced changes in the chemical shift (SCS) were correlated with a dual substituent parameter equation. The contributions of conjugative (rho(R)) and nonconjugative effects (rho(F)) were analyzed, and mapping of the substituent-induced changes is given over the entire isoquinoline moiety for both series. The experimental results can be rationalized with the aid of the resonance polarization concept. This means the consideration of the substituent-sensitive balance of different resonance structures, i.e., electron delocalization, and the effect of the aromatic ring substituents on their relative contributions. With tetrahydroisoquinolines, the delocalization of the nitrogen lone pair (stereoelectronic effect) particularly contributes. Correlation analysis of the Mulliken atomic charges for the dihydroisoquinoline derivatives was also performed. The results support the concept of the substituent-sensitive polarization of the isoquinoline moiety even if the polarization pattern achieved via the NMR approach is not quite the same as that predicted by the computational charges. Previously the concepts of localized pi- polarization and extended polarization have been used to explain polar substituent effects within aromatic side-chain derivatives. We consider that the resonance polarization model effectively contributes to the understanding of the polar substituent effects Y1 - 2005 ER - TY - JOUR A1 - Klinka, Karel D. A1 - Imrich, Jan A1 - Danihel, I. A1 - Bohm, Stanislav A1 - Kristian, Pavol A1 - Harnul'akova, S. A1 - Pihlaja, Kalevi A1 - Koch, Andreas A1 - Kleinpeter, Erich T1 - Configuration and E/Z interconversion mechanism of O(S)-allyl-S(O)-methyl-N-(acridin-9-yl)iminothiocarbonate N2 - The configuration and dynamic behavior of O-allyl-S-methyl-N-(acridin-9-yl)iminothiocarbonate (1) and its S- allyl-O-methyl regioisomer (2) were studied using quantum chemical calculations and by applying a novel graphical method to scatter maps obtained from MD simulations for evaluation of an NOE-weighted internuclear distance (r(NOE)). Energy calculations indicated that the Z configuration was predominant for each compound and, further, this was supported both by the calculated chemical shifts and the rNOE. Both N-inversion- and rotation-type transition-state structures were also calculated for the E/Z isomerization process, the results indicating that the preferred interconversion mechanism for 1 is N-inversion, but contrastingly, interconversion via rotation is equally as probable as N-inversion for 2. This supports the notion that one or the other or both pathways can be active and each system needs to be assessed on a case- by-case basis. Copyright (c) 2005 John Wiley & Sons, Ltd Y1 - 2005 SN - 0749-1581 ER -