Synthesis of 3‐Amino‐1‐(difluoromethylidene)tetralins via Relay Photocatalytic Cascade Reactions of Arylalanines and 2‐Bromo‐3,3,3‐trifluoropropene

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A relay photocatalytic cascade reaction for the synthesis of 3‐amino‐1‐(difluoromethylidene)tetralins was described. The reaction used readily available N ‐Boc protected arylalanines and bulk industrial chemical 2‐bromo‐3,3,3‐trifluoropropene (BTP) as the starting materials combining two photoredox catalytic cycles with a single photocatalyst. In the first catalytic cycle, the defluorinative coupling of N ‐Boc arylalanines with BTP provided 2‐bromo‐1,1‐difluoroalkenes. In the second catalytic cycle, 2‐bromo‐1,1‐difluoroalkenes underwent intramolecular radical cyclization by photoredox activation of C( sp 2 )−Br bond, affording the desired 3‐amino‐tetralins bearing an exo ‐difluoroethylene unit in good yields. Moreover, the reactions of 3‐aryl propanoic acids and BTP for the construction of 1‐(difluoromethylidene)tetralins were also demonstrated. magnified image