Synthesis of 2-Sulfonyl Indenes and Indanes

Triflic Acid-Catalyzed Synthesis of Indole-Substituted Indane Derivatives via In Situ Formed Acetal-Facilitated Nucleophilic Addition and 4π-Electron-5-Carbon Electrocyclization Sequence

An efficient protocol for the synthesis of indole-substituted indanes from o-alkenylbenzaldehydes under acetalization conditions has been presented. The cyclization occurs via a nucleophilic addition of indole on the oxacarbenium ion generated from acetal formed under the reaction condition followed by a conrotatory 4π-electrocyclization reaction, which takes care of the exclusive diastereoselectivity observed during the cyclization step. Olefin geometry of o-alkenylbenzaldehyde and the amount of indole play a decisive role in the success of this cyclization process.

Recent advances in the synthesis and applications of β-keto sulfones: new prospects for the synthesis of β-keto thiosulfones

This review mainly focuses on recent developments in the preparation of β-keto sulfones and their extensive synthetic applications. New prospects for the synthesis of β-keto thiosulfones have also been highlighted. Over the last decade, there has been exponential growth in the direct construction of β-keto sulfones using a wide variety of keto and sulfonyl precursors. Of note, the most promising photoredox transformations and electrochemical synthesis methods of β-keto sulfones are also presented. Moreover, β-keto sulfones are versatile building blocks in organic synthesis due to their three essential functional groups: sulfonyl, carbonyl, and active methylene moieties. The convenient preparation of β-keto sulfones allows the synthesis of many valuable carbocyclic and heterocyclic compounds, and the effortless removal of the sulfonyl moiety via transformations is supported. The chemistry of β-keto sulfones (2013 to present) can be divided into several sections based on the sulfonyl surrogates, and ubiquitous synthetic strategies were systematically outlined.

Grignard-Reagent-Promoted Desulfonylation/Intramolecular Coupling for the Synthesis of 2-(1-Fluorovinyl)pyridines

A novel process involving Grignard-reagent-promoted desulfonylation/intramolecular coupling of readily available α-fluoro-α,β-unsaturated-(2-pyridyl)sulfones was realized that provided a series of polysubstituted 2-(1-fluorovinyl)pyridines in good yields. The intrinsic coordination between pyridine and Mg(II) along with the "negative fluorine effect" of the substrates should play the key role for the smooth transformation in the absence of transition-metal catalysts.