Synlett

The intramolecular carbolithiation of alkynes is a useful cyclization reaction that gives stereoselective access to functionalized alkenes. This reaction is supposed to proceed through a syn-addition mechanism. We show in this account that the interaction between the lithium cation and the substituent on the propargylic position (or directly on the triple bond) can derail this process and afford selectively the anti-addition product. The set of results presented in this account, both experimental and theoretical, suggests that the stereochemical outcome of the addition can be predicted with success.

The palladium-catalyzed cyanation of aryl halides has been accomplished for the synthesis of aryl nitriles using the electrophilic N–CN reagent as a cyanating reagent. The method utilizes a mild base and a substoichiometric amount of zinc as a promotor and offers a mild cyanation that tolerates various functional groups to afford aryl nitriles in good to excellent yields. Preliminary mechanistic investigation revealed the important role of the methylene linkage and the reductant.

Herein, we have developed an Amberlyst-15-catalyzed oxidative cyclization strategy for the synthesis of biologically active pyrrolo[1,2-a]quinoxaline scaffolds. The advantages of the present protocol include catalyst recovery and reuse, along with simpler reaction conditions compared to previously reported methods.

Synlett 2025; 36: V-IXDOI: 10.1055/a-2737-9790Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

We report a light-induced, iron-promoted method for the synthesis of polyaromatic benzotetraphenone derivatives via a tandem [2+2] Paternò–Büchi photorearrangement/electrocyclization pathway. Irradiation of anthraquinone with diphenylacetylenes under 370 nm LED light in the presence of FeCl₃ afforded novel polyaromatic scaffolds in excellent yields. The structures of the products were confirmed by single-crystal X-ray diffraction, revealing planar, rigid frameworks with promising photophysical properties. This strategy offers a new platform for constructing highly conjugated, luminescent molecules from simple precursors under mild conditions.

A cobalt(III)-catalyzed regioselective coupling of indolines with allenes is reported to access C7-alkenyl indolines in good to high yields. The method features weakly coordinating-group assistance, broad functional-group tolerance, including pharmacophores, scalability, and a reversible C–H activation step.

Although the 1,3-hydroxy migration reaction of arylvinyl carbinols is a valuable molecular transformation, examples of Lewis acid-catalyzed reactions remain quite limited. We found that the target Lewis acid-catalyzed reaction proceeded smoothly when acetone was used as the reaction medium. This catalytic system was applicable to arylvinyl carbinols having electron-deficient aromatic rings, a little-studied and challenging topic in 1,3-hydroxy migration chemistry.

Vinyl cyclopropanes are valuable functional groups in drugs or natural products as well as established precursors to trigger a rich variety of synthetic transformations. However, their reactive nature makes their installation challenging. We herein present a modular access to highly diastereoselective (>20:1) dienal-cyclopropanes from rhodium-enalcarbenoids and styrenes under mild conditions. This protocol was extended to synthesize a biologically relevant substituted pyrroline scaffold. Overall, this Rh (II)-catalyzed cyclopropanation exhibits good functional group tolerance, facile scalability, and selective access to a diverse range of dienal cyclopropane motifs featuring an all-carbon ε-quaternary stereocenter.

The Cp2TiCl-mediated opening of epoxides in α,β-unsaturated ester-appended substrates leads to a cascading 5-exo-trig radical cyclization followed by lactonization yielding bicyclic lactone rings. Leveraging this strategic approach has become crucial in the construction of the core structure of many terpenoid natural products. In our present study, this methodology is further extended to the maleate/fumerate diester–appended substrates to give selectively only the 5-exo ring closure products with the [5,5] bicyclic lactone framework. This arranged the basis of a facile approach to attempt the synthesis of lingzhilactone B, an important Ganoderma meroterpenoid with two all-carbon quaternary chiral centers in the ring junction, from easily available starting materials. The modular strategy developed here can pave the synthetic pathways for many other natural products of this genre.

A novel iron-catalyzed reaction has been developed for the preparation of various vinyl sulfides. This new method enables a range of thioketals to easily access terminal alkenes featuring different alkylthio groups. 28 sulfanes have been efficiently achieved with moderate to good yields. A preparative-scale reaction also proceeds well, demonstrating its further potential in organic synthesis. We further tried to understand its mechanism by DFT calculations. This methodology is significant in sulfur chemistry, giving a new pathway to transform thioketals to vinyl sulfides.