Epoxides reaction with sulfide ions

In the reaction of 2-hydroxyalkyl halides with cyanide ions the intermediate formation of oxiranes can give rise to rearrangement products. Epoxides may also be encountered if CN ions are reacted with a-halo ketones (Scheme On heating with quaternary ammonium halides in acetonitrile or DMSO at 80-130 C these cyanooxiranes (3) are converted into 2-cyano ketones (4). Phenacyl bromide, in contrast, gives rise to 3-oxo-3-phenylpropionitrile (5) on treatment with cyanide ions. Not much is known about the reaction of the corresponding a-halo sulfides with cyanide ethylthioacetonitrile was obtained from the chloro sulfide by treatment with Hg(CN)2. ... 

Like phenols, thiols also react with epoxide groups to form hydroxyl sulfides as shown in reaction (81). It was originally believed that thiols are unreactive with epoxides. However, it has been shown recently that, in the presence of suitable catalysts, epoxy-thiol reactions are several times faster than epoxy-amine reactions, particularly at low temperatures. Reaction (81) is very selective and no side reactions have been observed in this case. The reaction has been found to be accelerated by the presence of amines and two alternative reaction routes have been suggested to explain the formation of sulfide ion intermediate (Schemes 27 and 28), which then reacts with the thiol. 

Isolation of eryttro-2-inerceptO 3-buta o] by Price and Kirk1 8 from the condensation of hydrogen sulfide with fMMm- i.S epoxybutwu illustrates the Btereochemioally specific character of the reaction (Eq. 637). In this, as well as other reactions involving epoxides less reactive than ethylene oxide, it is necessary to operate in the prcwru.i-of base. Failure to do so leads to a low reaction rate because of the small HS- ion concentration in neutral solution. 

Treatment of 2,3 Cpoxy-l-amines with Lewis acid induces a rearrangement to aziridinium ions that react efficiently with a nucleophiles to give functionalized hydroxy sulfides or hydroxy amines (Equation 23) <1997SL11>. Under the influence of ethylaluminium chloride, an epoxide tethered to an azide undergoes Lewis acid-assisted cyclization followed by an intramolecular Schmidt reaction and subsequent in situ reduction of the intermediate iminium species upon addition of sodium borohydride (Scheme 8). This protocol was used as a key step in a novel synthesis of indolizidine alkaloids of pharmaceutical interest <20030L583, 2004JOC3093>. 

The scope of cyclodestannylation as a method for the synthesis of cyclopropyl compounds appears to be limited. Whereas tributyl(norborn-2-en-5-yl)tin gives the nortricyclic sulfide 12 in 75% yield, bromination of tributyl(cylohex-3-en-yl)tin at — 65°C does not lead to the anticipated 2-bromobicyclo[3.1.0]hexane. Unexpectedly, the cyclodestannylation of tributyl(3-methyl-2-enyl)tin with a sulfenyl chloride also fails, although a Markovnikov addition to the double bond would have formed a tertiary carbenium ion y to tin. Instead an SE2 reaction results to give an allylic sulfide. Addition of 3-chloroperoxybenzoic acid to but-3-enyltin does not lead to any cyclodestannylation. Instead, the corresponding tributyl(3,4-epoxybutyl)tin is obtained in 78% yield. This epoxide readily undergoes a 1,3-elimination reaction to cyclo-propylmethanol using both Lewis and protic acids.13... 

Neumann and co-workers have used sandwich-type polyoxometalates as catalysts for such reactions.305 The sandwich consists of transition metal ions between two Keggin anions, as in Ki2WZnMn(II)2(ZnW9034)2. In some cases, quaternary ammonium salts were used as the cations to take the catalyst into organic solvents. Sulfides were oxidized to sulfoxides with 30% aqueous hydrogen peroxide in 85-90% yields, with some sulfone also being formed. The system was more than 99% selective in the conversion of cyclooctene to its epoxide. The system also shows good selectivity between double bonds (6.57), probably the result of the bulky anion and the increased electron density in alkyl-substituted double bonds. 

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