Catalyst-dependent selectivity in sulfonium ylide cycloisomerization reactions

Abstract

An unusual example of π-acid catalyst-dependent selectivity in the cycloisomerization of alkene-tethered sulfonium ylides affords cyclopropanes or dihydrofurans with excellent control of chemoselectivity.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

“…Recently, the group of Maulide also reported the cyclopropanation of sulfur ylides with S-tethered olefins. 355 The cyclopropanation of sulfur ylide 623 , carrying two olefins, showed high selectivity for the S-tethered olefin, affording product 624 in 75% yield (Scheme 110). Interestingly, the authors describe a catalyst-dependent cyclization, where other π-acidic catalysts such as Pd(II) and Pt(II) salts selectively afforded dihydrofuran 625 in moderate to excellent yields.…”

Gold‐Catalyzed Cycloisomerization of Sulfur Ylides to Dihydrobenzothiepines

“…[24] Whilst the majority of the initial studies wereb ased on non-stabilized sulfonium and sulfoxonium ylides, modern work exploits the reactivityo f their stabilized surrogates, in which electron density from the ylidic carbon is distributed to one or two electron-withdrawing functionalities. This in turn enables the utilization of these sulfur ylides as practical and bench-stable reagents as well as the development of novel reactivity.I ndeed, applicationso f stabilized sulfonium and sulfoxonium ylides have been expanded to encompass noble transition metal catalysis, [8,9,25] in particularAu I .…”

“…Recently,our group has reported that gold-catalyzed electrophilic activation of alkenes allows the construction of highly functionalized cyclopropane scaffolds. [25][26][27][28][29][30] Prior to that, we [31] and others [32] have demonstrated the synthesis of multisubstituted furan cores throughg old-catalyzed activation of alkynes in the presence of sulfonium ylides, either in intra-or intermolecular fashion. Interestingly,t he majority of these and related transition metal-catalyzed reactions of sulfur ylides mostly employ variations on substituents tethered to the ylidic carbon.O nt he other hand, only minor variations on the sulfur substitution have been reported, [25,30] probably due to the fact that most of those transformationse ventually result in elimination of the sulfur tether during the reaction, thus, leading to stoichiometric sulfide byproducts (cf.…”

“…Given our recent experience in the cycloisomerization of Shomoallyl sulfonium ylides (Scheme 1a,i ), [25] we becamei nterested in exploring the reactivity of analogous S-homopropargyl sulfonium ylides. In this regard,i nitial experiments involved the reactiono ft he readily availables ulfonium ylide 1a [33] with JohnPhos Au(MeCN)SbF 6 (5 mol %) in MeOH at room temperature, aiming at the formation of at risubstituted furan,i nspired by ap rior study of our group (Scheme 1a iv).…”

A Catalytic Cross‐Olefination of Diazo Compounds with Sulfoxonium Ylides

“…Sulfonium and sulfoxonium ylides have witnessed a renaissance in contemporary catalysis beyond the well‐known Johnson–Corey–Chaykovsky reactions,8 namely in C−H functionalisation,9 N−H insertion,10 and cycloisomerisation reactions 11. Their popularity is owed to the fact that they are easy to prepare, readily purified, and considerably safer to handle than their diazo counterparts.…”