Reaktion von Dehydrobenzol mit Thioäthern

Abstract

Dehydrobenzol reagiert mit Dimethylsulfid zu einem Ylid, das durch überschüssige lithiumorganische Verbindung stabilisiert wird. Durch Zugeben von HClO4 entsteht daraus Dimethyl-phenyl-sulfoniumperchlorat. In Abwesenheit eines Stabilisators zerfällt das Ylid in Polymethylen und Methyl-phenyl-sulfid. Mit höheren Dialkylsulfiden reagiert Dehydrobenzol unter Spaltung der Thioätherbindung und Bildung von Alkyl-phenyl-sulfid und Olefin. Das intermediär gebildete Ylid stabilisiert sich also durch intramolekulare Hofmann-Eliminierung. — Dimethyl-phenyl-sulfoniumperchlorat setzt sich mit Kalium-tert.-butylat in wasserfreiem Dimethylsulfoxyd zu Äthylen, Isobutylen und Methyl-phenyl-sulfid um. Die Hofmann-Eliminierung verläuft bei Sulfoniumsalzen in Dimethylsulfoxyd besonders glatt. Dimethyl-cyclooctyl-sulfoniumjodid ergibt ein Gemisch von 92.4% cis- und 7.6% trans-Cycloocten. — Bei der Umsetzung von lithium-organischen Verbindungen mit Triphenylsulfoniumbromid bildet sich in geringer Ausbeute Dehydrobenzol; Hauptreaktionen sind die Bildung einer instabilen Zwischenstufe mit vierbindigem Schwefel und eine Austauschreaktion

The Epoxidation of Carbonyl Compounds with a Benzyne-Triggered Sulfur Ylide

“…17,18 Since the early 1960s, the benzyne triggered method for the preparation of sulfur ylides has emerged (Scheme 1, method A, path 4). [19][20][21] The ylide was generated in situ from a thioether with benzyne, and the trapping of ylide with N-methyl isatins gave the corresponding spiroepoxy oxindoles. 22 Besides thioethers, a practical alternative approach utilizing the sulfoxides as the starting materials for the generation of stable ylides was chosen (Scheme 1, method B).…”

“…Since the early 1960s, sulfur ylides have emerged as reactive nucleophilic alkylidene transfer agents in organic syntheses. − This class of intermediates has been found to have wide applications in the synthesis of epoxides, , cyclopropanes, aziridines, − terminal alkenes, and organoboron compounds. , The most common method of sulfur ylide generation consists of proton abstraction from the corresponding sulfonium salts, which are available by the direct alkylation of thioethers (Scheme , method A, path 1). , A less common but exceedingly useful approach for the generation of sulfur ylides involves the reaction of a thioether with a carbene or a metal carbenoid (Scheme , method A, path 2) . Forbes and co-workers developed a new strategy for the synthesis of sulfur ylides, which is based on the alkylation of thioethers with 2-bromoacetic acid and the decarboxylation of in situ generated sulfonium (Scheme , method A, path 3). , Since the early 1960s, the benzyne-triggered method for the preparation of sulfur ylides has emerged (Scheme , method A, path 4). − The ylide was generated in situ from a thioether with benzyne, and the trapping of ylide with N -methyl isatins gave the corresponding spiroepoxy oxindoles . Besides thioethers, a practical alternative approach utilizing sulfoxides as the starting materials for the generation of stable ylides was chosen (Scheme , method B) .…”

Schwefelylide durch (3+2)‐Cycloaddition von Arinen mit Vinylsulfiden – stereoselektive Synthese hoch substituierter Alkene

“…Die Reaktion von Arinen mit Thioethern wurde überraschenderweise bisher nicht umfassend untersucht . Bislang wurde diesbezüglich gezeigt, dass bei Einsatz eines Alkylthioethers, der ein α‐CH‐Proton trägt, das primäre Arin‐Zwitterion einen schnellen intramolekularen 1,4‐Protontransfer durchläuft und so das entsprechende Schwefelylid erzeugt (Schema b), das anschließend zu wertvollen Produkten weiterreagieren kann …”

Reactions of HDDA-Derived Benzynes with Sulfides: Mechanism, Modes, and Three-Component Reactions

“…Its reaction with sulfide trapping agents, largely by way of ylide intermediates (Figure 1), was studied in a number of laboratories in the period 1962 1 –1989 2 but has lain fallow until the recent report of Xu and coworkers. As they pointed out, “nucleophilic attack of alkyl thioether on benzyne followed by an intramolecular 1,4-proton shift has been almost totally neglected since its debut 3 .” 4 The majority of those early studies were described in a series of reports from the Nakayama laboratory.…”

“…o -Benzyne ( 1 ) is the parent member of one of the most versatile of all reactive intermediates in organic chemistry, largely because of its adaptability as an electrophilic agent capable of capture by many different types of external nucleophiles. Its reaction with sulfide trapping agents, largely by way of ylide intermediates (Figure ), was studied in a number of laboratories in the period 1962–1989 but has lain fallow until the recent report of Xu and co-workers. As they pointed out, “nucleophilic attack of alkyl thioether on benzyne followed by an intramolecular 1,4-proton shift has been almost totally neglected since its debut” .…”