Dithiane Induced Cycloaddition/Aromatization Tactic for the Synthesis of Multisubstituted Furans

Abstract

The development of a new transition-metal-free tactic for convergent, one-pot synthesis of multisubstituted furans by β-chloro-vinyl dithiane cyclization with aldehydes is described. Key to the success was the development of a new vinylidene dithiane site as a donor allene that generates the active dihydrofuran, which undergoes in situ aromatization under mild conditions.

Direct Regioselective [3 + 2]-Cyclization Reactions of Ambivalent Electrophilic/Nucleophilic β-Chlorovinyl Dithianes: Access to Cyclopentene Derivatives

“…Among various types of organic reagents, dithiane compounds serve as valuable umpolung intermediates in the field of synthetic organic chemistry because of their unique properties and reactivities. − Recently, the demonstrated ambivalent donor–acceptor (D–A) reactivities of β-chlorovinyl dithianes in our group have opened up a novel class of reaction pathways beyond the typical dithiane methods . The development of [3 + 2]-cycloaddition has been achieved through identification of reactive vinylidene dithiane species and aldehydes .…”

“…Our investigations commenced with the cyclization of equimolar amounts of β-chlorovinyl dithiane 1a and chalcone 2a under the previously reported conditions . As shown in Table , we found promising results when employing an excess amount of base (3.0 equiv t -BuOK in DMSO).…”

Lewis Acid Promoted Stereoselective Synthesis of Polysubstituted 1,3‐Dienes via a Dual 1,3‐Sulfur Rearrangement

“…[8] Our research group has demonstrated the potential transformations of β-chlorovinyl dithianes with unsaturated compounds for the synthesis of highly substituted 1,3-dithianes, which are versatile umpolung acyl building blocks in organic synthesis. [9] Based on previous studies, [10] it has been shown that the dithianyl ring opening of the vinyl dithianes results in a vinyl- thionium ion under acidic conditions that could directly engage in CÀ C bond formation with a range of nucleophilic reagents and alkenes. With this in mind, we focused on developing a set of transition-metal-free conditions for the straightforward synthesis of highly dithianyl substituted dienes by exploiting the Lewis acid-promoted cross-coupling of β-chlorovinyl dithianes and alkenes (Scheme 1d).…”