COMPLETE ASSIGNMENT OF H-1 AND C-13 NMR-SPECTRA OF CHLOROBENZANTHRONES

H-1 and C-13 NMR studies were carried out on benzanthrone and 3-, 4-, 6-, 8-, 9-, 10- and 11-chlorobenzanthrone. Complete assignments of pro ton and carbon resonances were made with the aid of HH-COSY, NOESY, CH -COSY and HMBC techniques. Substitution effects of a chlorine atom are not large, but give a systematic change particularly in C-13 shift va lues. The anomalous downfield shift of the H-1 signal in 11-chlorobenz anthrone was explained by the electrostatic attraction between the ele ctronegative Cl atom, based on the result of an MNDO-PM3 calculation.