Distinctive Reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under Photoredox Catalysis

Abstract

A simple photocatalytic method was developed for the synthesis of unsymmetrical 1,2-diamines by the unprecedented reductive coupling of N-benzylidene-[1,1'-biphenyl]-2-amines with an aliphatic amine. The presence of phenyl substituent in the aniline moiety of the substrate was critical for the reactivity. The reaction proceeded via radical-radical cross-coupling of a-amino radicals generated by proton-coupled single-electron transfer in the presence of an Ir-photocatalyst. On the other hand, symmetrical 1,2-diamines were selectively produced from the same starting materials by judicious choice of the reaction conditions, showcasing the distinct reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines. The developed method can be employed for the synthesis of various bulky vicinal diamines, which are potential ligands in stereoselective synthesis.

A Convergent Synthesis of Tetracyclic Indole Compounds by a ­Palladium-Catalyzed Cross-Coupling and Tandem Cyclization ­Reaction

“…With these optimized conditions in hand, we examined the scope of the reaction with respect to the substituents on the A ring moiety (Table 2 ). Sonogashira coupling of four N -tosyl- o -iodoanilide derivatives 15 – 18 possessing a methoxy, chloro, fluoro, or carbomethoxy group, respectively, 28 with alkyne 9 afforded the desired products 19 to 22 in yields of 78–85%. All the products underwent a cascade reaction under the optimized conditions to furnish the corresponding tetracyclic indoles 23 – 26 in yields of 70–77%.…”