A mild, copper-catalysed amide deprotection strategy: use of tert-butyl as a protecting group

Visible light-mediated dearomative spirocyclization/imination of nonactivated arenes through energy transfer catalysis

Aromatic compounds serve as key feedstocks in the chemical industry, typically undergoing functionalization or full reduction. However, partial reduction via dearomative sequences remains underexplored despite its potential to rapidly generate complex three-dimensional scaffolds and the existing dearomative strategies often require metal-mediated multistep processes or suffer from limited applicability. Herein, a photocatalytic radical cascade approach enabling dearomative difunctionalization through selective spirocyclization/imination of nonactivated arenes is reported. The method employs bifunctional oxime esters and carbonates to introduce multiple functional groups in a single step, forming spirocyclic motifs and iminyl functionalities via N-O bond cleavage, hydrogen-atom transfer, radical addition, spirocyclization, and radical-radical cross-coupling. The reaction constructs up to four bonds (C-O, C-C, C-N) from simple starting materials. Its broad applicability is demonstrated on various substrates, including pharmaceuticals, and it is compatible with scale-up under flow conditions, offering a streamlined approach to synthesizing highly decorated three-dimensional frameworks.

TMSN3 Initiated Electrochemical Mono-Dealkylation of Tertiary Amides

N-Dealkylation of amides is a general process in living organisms and organic synthetic chemistry, but an efficient chemical approach for this transformation has not been explored. Herein, we report an electrochemical method for the monodealkylation of a wide range of tertiary amides, including benzamides, alkyl amides, lactams, and sulfonamides. The reaction proceeds smoothly under mild conditions using TMSN3 as the initiator and is not limited to deethylation or demethylation. This protocol enables the large synthesis, providing a valuable tool for synthetic organic chemistry.

Organocatalytic Deoxygenative [3+2] Cycloaddition of N-Hydroxyamides with Alkynes to Access Isoxazoles

Although the transition-metal-catalyzed [3+2] cycloadditions to access isoxazoles have been described well, organocatalytic methods remain underdeveloped. Herein, we report the use of an organophosphine catalyst for the preparation of a series of isoxazoles with exceptional regioselectivity via the [3+2] cycloaddition of N-hydroxyamides and alkynes. The scope of this organocatalytic transformation is broad, tolerating numerous functional groups and proceeding uniformly in an environmentally friendly, simple, and efficient manner.

Total Synthesis of Lissodendoric Acid A

We describe a full account of our synthetic strategy leading to the first total synthesis of the manzamine alkaloid lissodendoric acid A . These efforts demonstrate that strained cyclic allenes are valuable synthetic building blocks and can be employed efficiently in total synthesis.

Total synthesis of lissodendoric acid A via stereospecific trapping of a strained cyclic allene

Small rings that contain allenes are unconventional transient compounds that have been known since the 1960s. Despite being discovered around the same time as benzyne and offering a number of synthetically advantageous features, strained cyclic allenes have seen relatively little use in chemical synthesis. We report a concise total synthesis of the manzamine alkaloid lissodendoric acid A, which hinges on the development of a regioselective, diastereoselective, and stereospecific trapping of a fleeting cyclic allene intermediate. This key step swiftly assembles the azadecalin framework of the natural product, allows for a succinct synthetic endgame, and enables a 12-step total synthesis (longest linear sequence; 0.8% overall yield). These studies demonstrate that strained cyclic allenes are versatile building blocks in chemical synthesis.

Highly congested spiro-compounds via photoredox-mediated dearomative annulation cascade

Photo-mediated radical dearomatization involving 5-exo-trig cyclizations has proven to be an important route to accessing spirocyclic compounds, whereas 6-exo-trig spirocyclization has been much less explored. In this work, a dearomative annulation cascade is realized through photoredox-mediated C-O bond activation of aromatic carboxylic acids to produce two kinds of spirocyclic frameworks. Mechanistically, the acyl radical is formed through oxidation of triphenylphosphine and subsequent C-O bond cleavage, followed by a 6-exo-trig cyclization/SET/protonation sequence to generate the spiro-chromanone products in an intramolecular manner. Furthermore, the protocol was extended to more challenging intermolecular tandem sequences consisting of C-O bond cleavage, radical addition to an alkene substrate, and 5-exo-trig cyclization to yield complex spirocyclic lactams.

pH-Dependent Conformational Switching of Amide Bonds─from Full trans to Full cis and Vice Versa

Strategies enabling the pH-dependent conformational switching of amide bonds from trans to cis, and vice versa, are yet limited in the sense that, in a suitable pH range, one rotamer may be stabilized to a large extent while the complementary pH range only leads to a mixture of isomers. By exploiting the effects of steric demand and the interaction of the amide carbonyl with a positive charge, we herein present the first examples for reversible pH-dependent switching from full trans to full cis.

Interfacing single-atom catalysis with continuous-flow organic electrosynthesis

The global warming crisis has sparked a series of environmentally cautious trends in chemistry, allowing us to rethink the way we conduct our synthesis, and to incorporate more earth-abundant materials in our catalyst design. "Single-atom catalysis" has recently appeared on the catalytic spectrum, and has truly merged the benefits that homogeneous and heterogeneous analogues have to offer. Further still, the possibility to activate these catalysts by means of a suitable electric potential could pave the way for a true integration of diverse synthetic methodologies and renewable electricity. Despite their esteemed benefits, single-atom electrocatalysts are still limited to the energy sector (hydrogen evolution reaction, oxygen reduction, etc.) and numerous examples in the literature still invoke the use of precious metals (Pd, Pt, Ir, etc.). Additionally, batch electroreactors are employed, which limit the intensification of such processes. It is of paramount importance that the field continues to grow in a more sustainable direction, seeking new ventures into the space of organic electrosynthesis and flow electroreactor technologies. In this piece, we discuss some of the progress being made with earth abundant homogeneous and heterogeneous electrocatalysts and flow electrochemistry, within the context of organic electrosynthesis, and highlight the prospects of alternatively utilizing single-atom catalysts for such applications.

Gram-Scale Preparation of Acyl Fluorides and Their Reactions with Hindered Nucleophiles

A series of acyl fluorides was synthesized at 100 mmol scale using phase-transfer-catalyzed halogen exchange between acyl chlorides and aqueous bifluoride solution. The convenient procedure consists of vigorous stirring of the biphasic mixture at room temperature, followed by extraction and distillation. Isolated acyl fluorides (usually 7–20 g) display excellent purity and can be transformed into sterically hindered amides and esters when treated with lithium amide bases and alkoxides under mild conditions.

Rh(III)-Catalyzed Annulation of Boc-Protected Benzamides with Diazo Compounds: Approach to Isocoumarins

A mild rhodium-catalyzed annulation of Boc-protected benzamides with diazo compounds via C−C/C−O bond formation has been explored. In the presence of [Cp*RhCl₂]₂, AgSbF₆ and Cs₂CO₃, Boc-protected benzamides can be effectively annulated to yield isocoumarins in 0.5–2 h.

Copper malonamide complexes and their use in azide–alkyne cycloaddition reactions

A series of copper(i) malonamide complexes have been synthesised and their catalytic activity explored in 1,3-dipolar cycloaddition reactions: the first time this ligand motif has been reported in a catalytic transformation.