Direct access to unnatural cyclobutane a-amino acids through visible light catalyzed [2+2]-cycloaddition

The first selective, photocatalyzed [2+2]-cycloaddition of dehydroamino acids with styrenetype olefins is presented. This simple, mild, and scalable approach relies on the use of the triplet energy transfer catalyst [Ir(dFCF3ppy2)dtbpy]PF6 under visible light irradiation and provides fast access to value-added substituted strained cyclobutane α-amino acid derivative