TY  - JOUR
A1  - Modarresi-Alam, Ali Reza
A1  - Alsadat Amirazizi, Homeyra
A1  - Bagheri, Hajar
A1  - Bijanzadeh, Hamid-Reza
A1  - Kleinpeter, Erich
T1  - Dynamic 1H NMR spectroscopic study of the ring inversion in N-sulfonyl morpholines-studies on N-S interactions
N2  - The effect of the exocyclic conjugation, via d;p orbital interaction and/or negative hyperconjugation (anomeric effect) of the N;S bond, on the inversion of the morpholine ring in some N-arylsulfonyl morpholines is studied by variable-temperature 1H NMR spectroscopy in different solvents. The observed free energy barriers are 9.2;10.3 kcal mol;1; the lower values were obtained with increasing conjugation (substituents of higher electron withdrawing power) along the series. The barrier to ring inversion of 1e was solvent independent. X-ray data of compounds 1b,d reveal the chair conformation of the six-membered ring, the flattened pyramidal orientation of the ring nitrogen atom, and the sulfonyl group in equatorial position with the plane containing the Caryl;S;N bond perpendicular to the plane of the benzene ring. In addition, the sulfonamide group prefers a conformation with the S;C bond antiperiplanar with respect to the nitrogen atom lone pair and the ;CH2;N;CH2; moieties in staggered conformation with the S;O bonds of the SO2 group.
Y1  - 2009
SN  - 0022-3263
ER  - 
TY  - JOUR
A1  - Modarresi-Alam, Ali Reza
A1  - Amirazizi, Homeyra Alsadat
A1  - Bagheri, Hajar
A1  - Bijanzadeh, Hamid-Reza
A1  - Kleinpeter, Erich
T1  - Dynamic H-1 NMR spectroscopic study of the ring inversion in N-sulfonyl morpholines : studies on N-S interactions
N2  - The effect of the exocyclic conjugation, via d-p orbital interaction and/or negative hyperconjugation (anomeric effect) of the N-S bond, on the inversion of the morpholine ring in some N-arylsulfonyl morpholines is studied by variable-temperature H-1 NMR spectroscopy in different solvents. The observed free energy barriers are 9.2-10.3 kcal mol(-1); the lower values were obtained with increasing conjugation (substituents of higher electron withdrawing power) along the series. The barrier to ring inversion of le was solvent independent. X-ray data of compounds 1b,d reveal the chair conformation of the six-membered ring the flattened pyramidal orientation of the ring nitrogen atom, and the sulfonyl group in equatorial position with the plane containing the C-aryl-S-N bond perpendicular to the plane of the benzene ring. In addition, the sulfonamide group prefers a conformation with the S-C bond antiperiplanar with respect to the nitrogen atom lone pair and the -CH2-N-CH2- moieties in staggered conformation with the S-O bonds of the SO2 group.
Y1  - 2009
UR  - http://pubs.acs.org/journal/joceah
U6  - https://doi.org/10.1021/Jo900454a
SN  - 0022-3263
ER  -