Mechanistic Studies on Garratt–Braverman Cyclization: The Diradical–Cycloaddition Puzzle

Utilizing the Pentadehydro-Diels-Alder Reaction for Polycyclic Aromatic Compound Synthesis: Diels-Alder-Based Linker Transformation

This study introduces a traceless linker strategy for pentadehydro-Diels-Alder (PDDA) cyclization, in which the sulfide/sulfone linker is strategically repurposed as a diene surrogate. As excellent electron-donating dienes, these linkers react with electron-deficient alkenes and alkynes, resulting in a series of highly selective cyclization products. This cascade reaction efficiently integrates the PDDA reaction with linker transformation, formally eliminating the need for permanent structural constraints. By exploiting the intrinsic reactivity of the linker, this strategy offers a robust and versatile approach to constructing complex polycyclic aromatic architectures, providing a powerful tool for organic synthesis.

Tetradehydro-Diels-Alder Reactions of Flexible Arylalkynes via Folding Inside a Molecular Cage

The tetradehydro-Diels-Alder (TDDA) reaction is a useful transformation for the rapid assembly of polycyclic scaffolds from simple linear precursors in a single synthetic step. However, the reaction requires careful substrate design and harsh reaction conditions to overcome the inherent entropic cost for this transformation. Herein we report an efficient site-selective TDDA transformation within a self-assembled Pd6L4 cage. Despite the large size, the flexibility of the employed substrates allows for efficient encapsulation within the host cavity. The rate of thermal cyclization of the encapsulated guest was found to be greatly enhanced, and high product selectivity for an unsymmetrical substrate was observed. The efficiency of this system relies on the precise conformational control of the substrate within the confined space of the host cage.

Benzene construction via Pd-catalyzed cyclization of 2,7-alkadiynylic carbonates in the presence of alkynes

A palladium-catalyzed highly regio- and chemo-selective cyclization of 2,7-alkadiynylic carbonates with functionalized alkynes to construct 1,3-dihydroisobenzofuran and isoindoline derivatives under mild conditions has been developed. Functional groups such as alcohol, sulfonamide, and indoles could be well tolerated. After careful mechanistic studies, a mechanism involving oxidative addition and regioselectivity-defined double alkyne insertions has been proposed.

Laser desorption ionization mass spectrometry: Recent progress in matrix-free and label-assisted techniques

The MALDI-based mass spectrometry, over the last three decades, has become an important analytical tool. It is a gentle ionization technique, usually applicable to detect and characterize analytes with high molecular weights like proteins and other macromolecules. The earlier difficulty of detection of analytes with low molecular weights like small organic molecules and metal ion complexes with this technique arose due to the cluster of peaks in the low molecular weight region generated from the matrix. To detect such molecules and metal ion complexes, a four-prong strategy has been developed. These include use of alternate matrix materials, employment of new surface materials that require no matrix, use of metabolites that directly absorb the laser light, and the laser-absorbing label-assisted LDI-MS (popularly known as LALDI-MS). This review will highlight the developments with all these strategies with a special emphasis on LALDI-MS.

Recent Advances in Phthalan and Coumaran Chemistry

Oxygen-containing heterocycles are common in biologically active compounds. In particular, phthalan and coumaran cores are found in pharmaceuticals, organic electronics, and other useful medical and technological applications. Recent research has expanded the methods available for their synthesis. This Minireview presents recent advances in the chemistry of phthalans and coumarans, with the goal of overcoming synthetic challenges and facilitating the applications of phthalans and coumarans.

Double SO2 Insertion into 1,7-Diynes Leading to Functionalized Naphtho[1,2-c]thiophene 2,2-dioxides

A novel metal-free double SO₂ insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO-bis(sulfur dioxide) under redox-neutral conditions, providing a range of dual sulfone-containing naphtho[1,2-c]thiophene 2,2-dioxides with generally high stereoselectivity. The reaction pathway is proposed to proceed through the sequence of arylsulfonyl-radical-induced 6-exo-dig/5-endo-trig bicyclization, H-abstraction, and diazotization.

A facile synthetic strategy to polysiloxanes containing sulfonyl side groups with high dielectric permittivity

Novel polysiloxanes containing sulfonyl side groups with high dielectric permittivity by thiol–ene post-polymerization reactions are presented.