Stereospecific synthesis of highly functionalized tricyclic beta-lactams by radical cyclizations using titanocene monochloride.

The reductive opening of epoxyimonobactams 1 with titanoncene (III) chloride gives rise to radicals that can be trapped by intramolecular pi systems (i.e., conjugated alkenes and lactone and amide carbonyls) in a stereospecific way to give new carbocyclic compounds such as tribactam 2.