Nuclear magnetic resonance of 1,4‐benzodiazepines. II Stereochemistry of 1,3‐dihydro‐2<i>H</i>‐1,4‐benzodiazepin‐2‐ones by lanthanide shift reagents

Abstract

Abstract The sterochemistry of some 1,3‐dihydro‐2 H ‐1,4‐benxodiazepin‐2‐ones, employed as psychotherapeutic agents, is deduced by proton magnetic resonance using the paramagnetic shift reagent Eu(fod) 3 . the lanthanide induced shifts are computer simulated on the basis of the geometric parameters of the protons in different model structures, having intermediate conformations between a cycloheptadiene‐ and a cyclohepatatriene‐like system. N‐Desmethyldiazepam shows a conformational equilibrium between two pseudoboat forms, while the 1‐alkyl substituted derivatives exist, at room temperature, in olny one boat cycloheptatriene‐like conformation.