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

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 CN 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 CN bond in a wide series of the related systems containing the CNSO 2 R moiety. Copyright © 2005 John Wiley & Sons, Ltd.