Results A solution (of la, containing 1 equiv of NCS in deuteriochloroform, was monitored by NMR. Within 15 min the simultaneous disappearance of the NCS singlet (6 2.94) and the AB quartet of the cephem C-2 protons (6 3.43) was observed. The formation of an unstable C-2 substituted A3-cephem, presumed to be the 2-chloro derivative 4a, was indicated by the appearance of the resonances shown in Table 1.5 Simultaneously, a non-p-lactam ...
