Jenseits der Pummerer‐Reaktion: Entwicklungen in der Chemie der Thioniumionen

Abstract

Seit den frühen 1960er Jahren hat sich die Pummerer‐Reaktion zu einem unentbehrlichen Syntheseverfahren in der organischen Chemie entwickelt. Viele interessante Fortschritte in den vergangenen Jahren unterstreichen die breite Anwendbarkeit und den Nutzen dieser Methode sowie die Vielseitigkeit von Thioniumionen als Intermediate.

The Effect of Sulfoxides on the Stereoselective Construction of Tetrahydrofurans: Total Synthesis of (+)‐Goniothalesdiol

“…www.chemeurj.org tive 7 by a Pummerer reaction. [34] We envisaged the formation of the heterocyclic moiety through the Et 3 SiH/ TMSOTf-promoted reductive cyclization reaction from bhydroxy sulfinyl ketone 8, which ought to be easily available through the well-established stereoselective reduction of enantiopure b-keto sulfoxides.…”

“…As shown in Scheme 8, the p-tolyl sulfinylmethyl group present in tetrahydrofuran 28 and C5 epimer 29, was subjected to Pummerer reaction conditions, [34,42] At this point, we considered simultaneously performing the reduction of the double bonds of the olefins and deprotection of the benzyl alcohols to complete the synthesis. However, the known fragility of the C-arylglycoside bond under hydrogenolytic conditions (H 2 , Pd/C, MeOH) [43] prompted us to try a stepwise hydrogenation and deprotection.…”

Fluoro-Pummerer rearrangement and analogous reactions

“…The mechanism of this fluorine insertion reaction is similar to that of the Pummerer rearrangement [43,46]. Formation of a carbenium/sulfonium ion II from the adduct of a sulfoxide with DAST (I) can be rationalized by a six-membered transition state in which nitrogen acts as a base.…”

Copper‐Catalyzed Extended Pummerer Reactions of Ketene Dithioacetal Monoxides with Alkynyl Sulfides and Ynamides with an Accompanying Oxygen Rearrangement

“…The Pummerer reaction has been extensively studied since its discovery in 1909 [1] and widely applied to the synthesis of natural products and biologically active compounds. [2] Mechanistically, the reactions are initiated by the activation of sulfoxides with acids (LA + ) and then nucleophiles (Nu À ) attack the resulting thionium ions to give the products [Eq. (1)].…”