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  -