Isothiourea-Catalyzed Asymmetric Synthesis of β-Lactams and β-Amino Esters from Arylacetic Acid Derivatives and N-Sulfonylaldimines

The isothiourea HBTM-2.1 (5 mol %) catalyzes the asymmetric formal [2 + 2] cycloaddition of both arylacetic acids (following activation with tosyl chloride) and preformed 2-arylacetic anhydrides with N-sulfonylaldimines, generating stereo-defined 2,3-diaryl-beta-amino esters (after ring-opening) and 3,4-diaryl-anti-beta-lactams, respectively, with high diastereocontrol (up to >95:5 dr) and good to excellent enantiocontrol. Deprotection of the N-tosyl substituent within the beta-lactam framework was possible without racemization by treatment with SmI2.