De Novo design and synthesis of dipyridopurinone derivatives as visible-light photocatalysts in productive guanylation reactions

Described here is the de novo design and synthesis of a series of 6H-dipyrido[1,2-e:2',1'-i]purin-6-ones (DPs) as a new class of visible-light photoredox catalysts (PCs). The synthesized DP1-5 showed their λAbs(max) values in 433-477 nm, excited state redox potentials E*1/2red and E*text-decoration:underline'1/2ox in 1.15−0.69 eV and -1.41−-1.77 eV (vs SCE), respectively. As a representative, DP4 enables the productive guanylation of various amines including 1o, 2o, and 3o-alkyl primary amines, secondary amines, aryl and heteroaryl amines, amino-nitrile, amino acids and peptides as well as propynylamines and α-amino esters giving diversities of biologically important guanidines and cyclic guanidines. The photocatalytic efficacy of DP4 in the guanylation overmatched commonly used Ir and Ru polypyridyl complexes, and some organic PCs. Other salient merits of this method include broad substrates scope and functional group tolerance, gram-scale synthesis, and versatile late-stage derivatizations that led to a derivative 78 exhibiting 60-fold better anticancer activity against Ramos cells with the IC50 0.086 μM than that of clinical drug Ibrutinib (5.1 μM).