Lewis acid-assisted N- fluorobenzenesulfonimide-based electrophilic fluorine catalysis in Beckmann rearrangement

Asymmetric Total Synthesis of Neobraclactone C

Asymmetric total synthesis of neobraclactone C was finished for the first time using the convergent synthetic strategy in 22 steps in the longest linear sequence from known materials. The key steps include a steric hindrance/hydrogen bond dual-controlled Heck arylation of α,β-unsaturated ketone to construct hemiketal and cis-alkenyl in one step and a CeCl₃-catalyzed tricycle formation.

La(OTf)3 facilitated self-condensation of 2-indolylmethanol: construction of highly substituted indeno[1,2-b]indoles

The Lewis acid-promoted self-condensation of 2-indolylmethanols has been revealed. On treatment with La(OTf)₃, highly substituted indeno[1,2-b]indole derivatives have been synthesized by using easily accessible 2-indolylmethanols with up to 94% yields. The utility of this method is further highlighted by evaluating the initial photophysical properties of some prepared products, indicating that the protocol may have potential applications in the construction of novel fluorescent materials.

Beckmann rearrangement catalysis: a review of recent advances

The Beckmann rearrangement is an elegant transformation and has been used to great success in the synthesis of natural products and pharmaceuticals. In this review, the role of different catalysts as well as different medium for Beckmann rearrangement has been discussed over the last 20 years.

N-Fluorobenzenesulfonimide as a highly effective Ag(i)-catalyst attenuator for tryptamine-derived ynesulfonamide cycloisomerization

N-Fluorobenzenesulfonimide was identified for the first time as a unique Ag(i)-catalyst attenuator in the annulation of a tryptamine-derived ynesulfonamide to an azepino[4,5-b]indole.

Beckmann Rearrangement of Ketoxime Catalyzed by N-methyl-imidazolium Hydrosulfate

Beckmann rearrangement of ketoxime catalyzed by acidic ionic liquid-N-methyl-imidazolium hydrosulfate was studied. Rearrangement of benzophenone oxime gave the desirable product with 45% yield at 90 °C. When co-catalyst P₂O₅ was added, the yield could be improved to 91%. The catalyst could be reused three cycles with the same efficiency. Finally, reactions of other ketoximes were also investigated.

Rapidly Activating Pd-Precatalyst for Suzuki-Miyaura and Buchwald-Hartwig Couplings of Aryl Esters

Esters are valuable electrophiles for cross-coupling due to their ubiquity and ease of synthesis. However, harsh conditions are traditionally required for the effective cross-coupling of ester substrates. Utilizing a recently discovered precatalyst, Pd-catalyzed Suzuki-Miyaura and Buchwald-Hartwig reactions involving cleavage of the C(acyl)-O bond of aryl esters that proceed under mild conditions are reported. The Pd(II) precatalyst is highly active because it is reduced to the Pd(0) active species more rapidly than previous precatalysts.