A novel visible-light-catalyzed tandem radical addition/ 1,5-hydrogen atom transfer/cyclization cascade of 2-alkynylarylethers with sulfonyl chlorides in 2-methyltetrahydrofuran was developed under photocatalyst-and additive-free conditions. This reaction relies on unique energy transfer and solvent-radical relay strategies to generate sulfonyl radicals for the preparation of a series of sulfonylfunctionalized dihydrobenzofurans in moderate to high yields catalyzed by visible light or solar radiation.
Five-membered N-heterocycles play an important role in organic synthesis and material chemistry, as they are widespread through pharmaceutical molecules and natural products. Chemists have developed many synthetic strategies for constructing five-membered N-heterocycles from N-centered radicals, but the availability of mild and green methods for these transformations is still limited. The cyclization of visible-lightgenerated N-centered radicals with alkenes has emerged as a powerful tool to enable these chemical transformations in recent years. Through chosen representative examples, the significant developments in this promising field were outlined, including the selection of catalysts, substrate scope, mechanistic understanding (especially density functional theory calculations), and applications. The contents of this Minireview are categorized by intramolecular cyclization and intermolecular Ncentered radical addition/cyclization reactions.
Two novel C(sp 3 )À H functionalization of inert alkanes and visible-light promoted oxidation decarboxylation of N-hydroxyphthalimide (NHP) esters to access polycyclic quinazolinones have been described. These methods do not involve metal catalysts and are carried out in water or water/DMSO media. The wide substrate scope, even including the seven-membered ring under mild reaction conditions, demonstrate the practicability of these strategies.[a] W.
Seven- and eight-membered rings widely exist in natural products and drugs. Meanwhile, considering the transition state nonbonding interactions and torsional strains, the flexible conformations and dense multi-ring skeleton, the synthesis...
The construction of all-carbon quaternary centers, especially those containing an alkyne-substituted framework, represents an important challenge in organic synthesis. Here we present a novel Fe-catalyzed selective formal insertion of diazo compounds into C(sp)−C(sp 3 ) bonds of propargyl alcohols under mild conditions that enables the streamlined construction of alkynesubstituted all-carbon quaternary centers. This unique strategy starts with in situ generation of an ester group in the presence of carboxylic acids, followed by insertion of metal-carbene into C(sp)− C(sp 3 ) bonds, which may open up a new reaction mode for exploring metal-carbene insertion into acyclic C−C bonds.
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