Synthesis of Novel β‐Lactams from Phenothiazin‐10‐ylacetic Acid

The first synthesis of 3‐phenothiazine‐β‐lactams is herein reported. Thirteen new derivatives of β‐lactams were synthesized using various Schiff bases and (phenothiazin‐10‐yl)acetic acid, which in turn was prepared starting from phenothiazine. The sole product of the Staudinger ketene–imine 2 + 2] cycloaddition reaction is the trans‐β‐lactam. All the synthesized compounds were characterized by elemental analyses and spectral (IR, ¹H‐NMR, and ¹³C‐NMR) data.