Allyl methyl sulphide

Scheme 1. Tungsten catalysed cross-metathesis of allyl methyl sulphide with pent-2-ene and but-2-ene...

The successful cross-metathesis of allyl methyl sulphide with ris-pent-2-ene and czs-but-2-ene, catalysed by the tungsten alkylidene 5, was reported by Basset and co-workers in 1993 [20] (Scheme 1). 

Using an equimolar quantity of allyl methyl sulphide and ds-pent-2-ene resulted in incomplete reaction of the allyl sulphide and some self-metathesis of the sulphide substrate. When an excess (4 equiv) of but-2-ene was used, however, the desired but-2-enyl sulphide was formed in a good yield at ambient temperature. In this case, the large quantities of unwanted hydrocarbon starting material and self-metathesis products were gaseous alkenes and therefore easily removed. Using a large excess of one alkene to improve the yield of the desired cross-metathesis product in this way is obviously only viable if this alkene is inexpensive and both it and its self-metathesis product are easily removed. 

The report by Basset and co-workers on the metathesis of sulphur-containing alkenes using a tungsten alkylidene complex, mentioned previously for the acyclic cross-metathesis reaction (see Sect. 2.2), also contained early examples of ring-opening cross-metathesis of functionalised alkenes [20]. Allyl methyl sulphide was reacted with norbornene in the presence of the tungsten catalyst 5, to yield the desired ring-opened diene 35 (Eq. 29). 

Unfortunately, this product was isolated as a mixture with diene 36, formed from cross-metathesis with a second equivalent of the allyl sulphide, and was contaminated with some polymeric residues. It is also important to note that an excess of the sulphide was required to suppress competing ROMP of the norbornene. A similar result was obtained for the reaction of allyl methyl sulphide with cyclop entene. 

In the presence of 12, allyl methyl sulphide undergoes self-metathesis leading to MeSCH2CH=CHCH2SMe (90% trans), and cometathesis with cw-but-2-ene leading to MeCH=CHCH2SMe (75% trans)m. 

Allyl methyl sulphide Allyl methyl disulphide Allyl methyl trisulphide... 

Both inorganic and organic hypochlorites may be used for the oxidation of sulphoxides. The cheapest method involves the use of a commercial bleach, such as Chlorox . Such a method is indeed successful for unsaturated sulphoxides such as allyl methyl sulphoxide although the yields are generally low. Other sulphoxides may also be oxidized by this method, for example, dimethyl sulphoxide gave bis(trichloromethyl) sulphone in low yield . In some cases bis(dichloromethyl) sulphone was also isolated in very low yield. This oxidation procedure is also commonly used by organosulphur chemists for the removal of unwanted odours, caused by sulphoxides (and sulphides), from dirty glassware. 

The essential oil, which is present in the fresh bulb in a concentration of 0.1 to 0.3%, contains diallyl sulphide, diallyl trisulphide and allyl methyl disulphide (derivatives of allicin) as main components. Apart from further allyl polysulphides, the steam distilled oil contains limonene as non-sulphurous component [111]. The high pungency of garlic oil makes it necessary to dilute it, commonly in vegetable oil. One gram of oil is equivalent to 900 g of fresh garlic or 200 g of dehydrated garlic powder [112]. 

Recognition of the role of sulphoxides in the inhibition chain has resulted in several studies of the autoxidation of mono- and disulphides (see later). In addition to the work by Hargrave [84], Bateman et al. [88— 90] have studied the oxidation of monosulphides, unsaturated monosulphides and cyclo-hex-2-enyl methyl sulphide. Allylic and vinylic sulphides were found to be much more reactive than saturated sulphides, although the methylene group, rather than the allylic double bond, was suggested to be the primary reaction centre. Reactivities were compared for the percentage yield of sulphoxide (A) and for the yield of hydroperoxide (B), viz. 

The thiols formed usually do not survive under the reaction conditions and cyclize to five- and six-membeied rings. Heating of allyl phenyl sulphide (94) in high boiling amines or carboxylic acids yields 2-methyl-2,3-dihydrobenzothiophene (95) and thiachroman (96). The two products are not interconvertible under these conditions. 

Raasch has extended his studies of the reactivity of bis(trifluoro-methyl)thioketen (141). Scheme 8 gives a survey of the reactions that have been carried out. Thus common nucleophilic agents such as alcohols, thiols, primary, and secondary amines, etc., react with (141) with conservation of the C=S double bond, whereas the C==C double bond remains in the products of the reactions of (141) with certain ethers, dimethylaniline, and hydrides of tin and silicon. Compound (141) reacted with a variety of olehnic substances in accordance with the general ene-reaction formalism, yielding allyl vinyl sulphides (148). The formation... 

Loss of catalytic activity resulting from internal displacements is not usually a serious problem below temperatures of about 100 C. However, highly active R-groups, such as benzyl, methyl and allyl, undergo internal displacement more readily, particularly in the presence of strong nucleopfiles. For instance, the presence phenolates and thiolates may lead to the formation of benzyl alcohol, ethers, or sulphides from benzyl-substituted quaternary ammonium salts. 

ETHYLENE GLYCOL ETHYL MERCAPTAN DIMETHYL SULPHIDE ETHYL AMINE DIMETHYL AMIDE MONOETHANOLAMINE ETHYLENEDIAMINE ACRYLONITRILE PROPADIENE METHYL ACETYLENE ACROLEIN ACRYLIC ACID VINYL FORMATE ALLYL CHLORIDE 1 2 3-TRICHLOROPROPANE PROPIONITRILE CYCLOPROPANE PROPYLENE 1 2-DICHLOROPROPANE ACETONE ALLYL ALCOHOL PROPIONALDEHYDE PROPYLENE OXIDE VINYL METHYL ETHER PROPIONIC ACID ETHYL FORMATE METHYL ACETATE PROPYL CHLORIDE ISOPROPYL CHLORIDE PROPANE... 

The addition of methoxide or cyanide ions to cyclopropene 280 gives ° mixtures of isomeric alkenes upon methylation or protonation via allyl anions. However, triphenyl-phosphine, -arsine, or -stibine, and dimethyl sulphide afford the corresponding ylides 281. Photochromic l,8a-dihydroindolizines result from reaction of spiroannelated cyclopropenes of the type 280 with pyridines. The synthesis proceeds to ylides of the type 281 which cyclize to give the observed products. 

When the two ortAo-positions are blocked, no parfl-Claisen products are observed. Heating of allyl 2,6-dimethylphenyl sulphide (111) yields a cleavage product 112 and four cyclic materials (113-116) which probably result from or/Ao-rearrangement followed by 1,3- and 1,4-methyl migrations . ... 

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