Catalyst-controlled cycloisomerization/[4 + 3] cycloaddition sequence to construct 2,3-furan-fused dihydroazepines and 2,3-pyrrole-fused dihydrooxepines

Abstract

A novel catalyst-controlled cycloisomerization/[4+3]cycloaddition sequence of readily available acyclic enyne-amides and crotonate-derived sulfur ylides is reported. This strategy enables the rapid and efficient construction of a series of bicyclic 2,3-furan-fused...

Manganese-mediated reductive N,N-dialkylation of nitroarenes: a dramatic NiI2 effect

“…16). 15–18 In addition, the use of nickel nano-powder (with 50 nm or 1 μm diameter) as the promoter could also deliver product 3a in 71% and 80% yields, respectively (entry 17). We envisioned that nickel nano-powder might react with 2a to form NiI 2 in situ .…”

“…(3) Of note, although nitroaromatics have been efficiently used in C–N bond forming reactions such as reductive cyclization, 14 monoalkylation, 15 arylation, 16 acylation, 17 and others 18 recently, our work represents the first highly chemoselective reductive dialkylation of cheap nitroaromatics with alkyl halides. (4) Furthermore, compared with previous elegant studies focusing on the monoalkylation of nitrobenezene, 15 the selective dialkylation in our study is non-trivial as it proceeds through a different intermediate and is able overcome both the problems of steric hindrance and chemoselectivity by avoiding the formation of the corresponding monoalkylation or quaternary ammonium salts. (5) NiI 2 has been identified as a powerful promoter in our case, distinct from the reported reductive coupling examples, and the nickel salt is responsible for the C–C coupling step.…”

Oxalates as Activating Groups for Tertiary Alcohols in Photoredox-Catalyzed gem-Difluoroallylation To Construct All-Carbon Quaternary Centers

“…All-carbon quaternary scaffolds are prevalent in natural products, synthetic pharmaceutics, and agrochemical ingredients . It is challenging to construct all-carbon quaternary centers by modern organic synthesis due to the inherent steric issues during the formation of these particular C­(sp 3 )–C­(sp 3 ) bonds.…”

“…It is challenging to construct all-carbon quaternary centers by modern organic synthesis due to the inherent steric issues during the formation of these particular C­(sp 3 )–C­(sp 3 ) bonds. Despite the challenges, remarkable advances have been made in this field, especially with the renaissance of radical chemistry …”

Direct Reaction of Nitroarenes and Thiols via Photodriven Oxygen Atom Transfer for Access to Sulfonamides

“…In Noël’s work, oxidation of the thiol is achieved by removal of electrons by the electrode, without the addition of any chemical oxidant. Other important methods that save one of the two redox steps include transition-metal-catalyzed sulfonamidation of aryl halides (Buchwald–Hartwig coupling or Ullmann type coupling), aryl boronic acids (Chan–Lam coupling), and arene C–H activations. , Recently, the related sulfinamide was reported to be formed from nitro molecules and thiols mediated by a metal photocatalyst . Despite the impressive progress, it remains challenging to completely remove these two separate redox steps and direct couple nitro compounds and thiols to form sulfonamides.…”