Conformation of 7‐chloro‐5‐phenyl‐ d 5 −3( S )‐methyl‐dihydro‐1,4‐benzodiazepin‐2‐one in solution

7‐Chloro‐5‐phenyl‐ d 5 ‐3( S )‐methyldihydro‐1,4‐benzodiazepin‐2‐one ( 1a ) was synthesized and its conformation in solution determined using a computer assisted LIS‐NMR method. It was found, with Fr(fod)‐ d 27 as a shift reagent, that a lanthanide coordinates to a carbonyl oxygen at a 2.02 Å distance (bond angle 158.07°, torsional angle 39.53°), while the substrate 1a adopts an expected quasi‐boat conformation with a C(3)‐methyl group exposed in a quasi‐equatorial position.