Synlett

The enantioselective desymmetrization of 2,2-disubstituted cyclohexane-1,3-diones has been realized through an unprecedented chiral-bisphosphine-catalyzed asymmetric Staudinger/aza-Wittig reaction. The key to this work’s success lies in utilizing an electronically rich and sterically hindered chiral bisphosphine reagent, namely DuanPhos, as a catalyst. In addition, a unique reductive system was established to address the requisite PIII/PV = O redox cycle. The mechanism of the chiral-bisphosphine-catalyzed asymmetric Staudinger/aza-Wittig reaction has been elucidated through combined computational and experimental studies. Several crinine-type amaryllidaceae alkaloids have been synthesized concisely, hinging on the newly developed methodology.

We report a one-pot base-free protocol for the oxidative olefination of benzylic amines promoted by a hypervalent iodine reagent for the synthesis of α,β-unsaturated ketones. Mechanistically, (diacetoxyiodo)benzene oxidizes the benzylic amine to the corresponding imine, which, on reaction with a phenacyl(triphenyl)phosphonium bromide salt and an in situ generated acetoxy anion leads to an α,β-unsaturated ketone. A wide range of α,β-unsaturated ketones were easily accessed through direct oxidative olefination of substituted benzylic amines in good to excellent yields and with high E-selectivity.

A synthesis of the C19–C30 segment of the neuroprotective natural product colletotrichamide A has been achieved by performing a Sonogashira coupling of two advanced intermediate fragments: a vinyl iodide and an alkyne. A Maruoka–Keck allylation, an Evans syn-aldol reaction, and Takai olefinations served as the key steps in the synthesis of the vinyl iodide intermediate, whereas glycosidation and Ohira–Bestmann reactions were used as the pivotal steps for accessing the advanced alkyne intermediate.

N-Arylated piperidones are present as pharmacophores in many pharmaceuticals and serve as useful precursors for the construction of important new molecules. We have developed a transition-metal-free, cost-effective, and mild approach for the synthesis of N-(hetero)arylated piperidones and their ketals by using ketals of piperidones and 2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles as precursors. The desired products were obtained in two steps: amination of the 2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitrile from piperidone, followed by ring transformation using a suitable nucleophile source. We have successfully tethered functionalized dihydrophenanthrenes, hydrobenzo[c]phenanthrenes, and benzoquinolines to piperidinone moieties under transition-metal-free conditions.

The bisoxindole motif is present in a variety of biologically active compounds. Here, we report an enantioselective oxidative homocoupling reaction of 2-oxindoles in the presence of a chiral bisguanidinium hypoiodite catalyst, providing access to the corresponding optically active bisoxindoles in excellent yields and with moderate to high diastereo- and enantioselectivities.

The C(sp3)–C(sp3) bond is one of the most prevalent motifs in organic compounds and holds significant importance in organic synthesis. The utilization of two alkyl electrophiles for cross-coupling stands as a vital strategy in building C(sp3)–C(sp3) bonds. Nowadays, synthetic electrochemistry is undergoing rapid development owing to its exceptional attributes not only in terms of green and economic properties by reducing the large amount of traditional chemical reductants, but also by its capacity to generate highly reactive radical intermediates under mild conditions, thereby opening up new reaction pathways and presenting novel opportunities to constructing C(sp3)–C(sp3) bonds. This article aims to comprehensively delineate the historical development of traditional electrophilic reagents in constructing C(sp3)–C(sp3) bonds, while also delving into the advantages of electrochemical electrophilic cross-coupling in this domain.1 Introduction2 Case Studies of Nickel-Catalyzed and Photochemical Alkyl Halide Cross-Coupling3 Case Studies of Electrocatalyzed Approaches for the Construction of C(sp3)–C(sp3) Bonds Using Electrophilic Reagents4 Nickel-Electrocatalyzed C(sp3)–C(sp3) Cross-Coupling of Unactivated Alkyl Halides5 Conclusion

Thiuram disulfides undergo a Cu(I)-catalyzed C–S cross-coupling with aryl iodides through Cu(OAc)2·H2O-assisted desulfurization to produce the S-thiocarbamate ester compounds efficiently. Various aryl iodides containing diverse substituents underwent a smooth reaction with a series of cyclic and acyclic secondary amine-based thiuram disulfides under an open-air atmosphere. A probable mechanistic pathway has been suggested based on control experiments and reports from the literature.

A cascade reaction involving a base-promoted nucleophilic substitution reaction between diketones and α-bromoacetophenone derivatives and the subsequent selective condensation–cyclization was developed for the synthesis of 1,2-diaroyl benzofurans. 1,2-Diaroyl benzofurans with different functional groups and structures exhibit reversible photochromic behaviors in solution, solid state, and thin films with diverse colors, demonstrating a potential application in the field of optical functional materials.

Herein, we present the synthesis of a novel 9,9′-bifluorenylidene-extended tetrathiafulvalene (TTF) as an E/Z isomeric mixture that was found to readily undergo an oxidative dimerization to furnish a TTF vinylogue with the two dithiafulvene units connected to an eight-membered ring fused to a bifluorenylidene core. This compound exhibited multiredox behavior and was found to take six charge states under cyclic voltammetry conditions: –2, –1, 0, +1, +2, +3. The dication corresponds to a cycloocta[1,2,3-jk:6,5,4-j′k′]difluorene with two appended 1,3-dithiolium rings.

Synlett 2024; 35: V-DOI: 10.1055/s-0043-1775055Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents