Enabled by electron donor–acceptor
complexes, a novel visible-light-induced
α-amino C–H bond arylation protocol, without a photoredox
catalyst, has been disclosed. The protocol does not require any transition
metal, oxidant, or exclusion of oxygen or moisture. A direct irradiation
of the mixture of tertiary amines and benzonitriles with visible light
in N,N-diethylethanamide in the
presence of Cs2CO3 afforded α-arylated
amines in good to excellent yields.
An Ag-catalyzed cyclization/demethylation of 2-alkynylthio (seleno)anisoles and 2-alkynyldimethylanilines is described and applied for the construction of valuable benzothio(seleno) phenes as well as indoles. Various 2-substituted benzothio (seleno)phenes and indoles were obtained in good to excellent yields under mild reaction conditions with low catalyst loading. An application of this new method is also exemplified with a concise synthesis of a bioactive molecule precursor. Furthermore, a conceivable reaction mechanism is proposed with supports from isotope-exchange experiments.
An
efficient method for the direct preparation of 3-aceto(cyano)methyl-substituted
benzothio(seleno)phenes has been achieved through C(sp3)–H bond activation of easily available acetone or acetonitrile
and cascade radical cyclization reaction. In this cascade radical
cyclization reaction, C(sp2)–C(sp3) and
C(sp2)–S bonds, as well as benzenethio(seleno)phene
skeletons, can be built along with the cleavage of the C(sp3)–S bond, demonstrating the high step-economics and efficiency
of this approach.
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