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Non-empirical calculations of NMR indirect spin-spin coupling constants. Part 13: configurational assignment of aminosulfonylamidines.

Krivdin LB, Larina LI, Chernyshev KA, Rozentsveig IB

A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky St. 1, 664033 Irkutsk, Russia. krivdin@irk.ru

Carbon-carbon coupling constants have been experimentally measured using the INADEQUATE pulse sequence in the series of N-[1,2-bis(dialkylamino)-2-arylethylidene]arylsulfonamides obtained from N-(1-aryl-2,2,2-trichloroethyl)amides of arylsulfonic acids. Comparison of the experimental J(C,C) in this series with those calculated at the SOPPA (Second-Order Polarization Propagator Approach) level in the model aminosulfonylamidine provided an unambiguous assignment at the C=N bond of the eight-title aminosulfonylamidines to E-configuration, while the unknown J(C,C) couplings in their inaccessible diverse Z isomers have been predicted with high reliability. The established marked difference between J(C,C) of the corresponding carbon-carbon bonds in cis and trans orientations to the nitrogen lone pair in aminosulfonylamidines provides a powerful tool in the configurational assignment at the C=N bond in a wide series of the related systems containing the C=N-SO2R moiety.

Published 3 October 2005 in Magn Reson Chem, 43(11): 937-42.
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