β-Lactams (including polycyclic) derived from chromium carbenes

The photolytic reaction of N-methylbenzylideneimine with 12-methoxypodocarpane chromium carbenes gave products derived either from carbon monoxide dissociation followed by 12-methoxy ligation or from oxidation of the carbene metal moiety, while the reaction of N-methylbenzylideneimine with 12-desmethoxy diterpenoid carbenes gave diterpenoid β-lactams. The relative stereochemistry of two monocyclic 3,4-diaryl β-lactams prepared from a methoxy- or ethylthio-phenylcarbene by photolysis with an imine has been determined by X-ray crystallography.