Microwave-Induced Enantiospecific Synthesis of trans-(3R,4R)-3-Acetoxy-4-aryl-1-(chrysen-6-yl)azetidin-2-ones via the Staudinger Cycloaddition Reaction of (+)-Car-3-ene with Polyaromatic Imines

The enantiospecific synthesis of 3-acetoxy-trans-β-lactams via the Staudinger [2+2] cycloaddition reaction of polyaromatic imines with bicyclic (+)-car-3-ene was investigated. The sterically hindered polyaromatic substituent at the N1 position in the imines plays a significant role, directing the cycloaddition reaction to stereoselective formation of trans-(3R,4R)-N-azetidin-2-ones. The results as described herein are highly unprecedented, since the synthesis of a single optically active trans-β-lactam, starting from a chiral ketene, has never been reported previously.