Allenyl methyl sulfoxide

A mixture of 100 ml of glacial acetic acid, 15 ml of 30% hydrogen peroxide and 5.0 g of allenyl methyl sulfoxide (see Chapter VII-1, Exp. 1) was heated for 30 min at 100°C. The colourless solution was cooled to 20°C and poured into 300 ml of ice-water. The sulfone was isolated by extracting the solution twelve times... 

Allenyl methyl sulfoxide, 197 - (2) Allenyl phenyl sulfoxides,... 

Allenyl methyl sulfoxide, 213 - (2) Methyl 1,2-pentadienyl sulfoxide, 213 - (3) Ethyl 1-propynyl sulfoxide, 214 - (4) Ethyl 1--propynyl sulfone, 214 - (5) Allenyl methyl sulfone, 215... 

Note 2. Traces of unreacted triethylamine might cause partial isomerization of the allenyl sulfoxide into the propargyl sulfoxide. The methyl iodide is added to ensure that no triethylamine remains. 

The reaction of 1,2-allenyl sulfoxides with sodium malonate also afforded 2-[bis (methoxycarbonyl)methyl]-2-alkenyl sulfoxides 177, which upon further transformation would provide an efficient access to butenolide derivatives 180 [90, 91]. 

The cycloaddition of allenyl sulfoxide 135 and cydopentadiene occurred at room temperature, giving the single adduct 136. The initially formed allylic sulfoxide underwent a rapid [2,3]-sigmatropic rearrangement. Treatment of 136 with trimethyl phosphite furnished alcohol 137. It should be noted that the reaction of methyl 4-hydroxy-2-butynoate with cydopentadiene failed to give 137. Thus, the allene 135 is considered as a masked and more reactive alkyne equivalent. 

The addition of an allyl alcohol to racemic allenyl sulfoxides results in vinyl ethers with the sulfinyl moiety at C-1 that undergo sigmatropic rearrangements upon distillation to produce 2,4-dienones after ehmination of sulfenic acid. In one example, an isomeric vinyl ether was obtained with a sulfinyl methyl substituent at C-2 that gave rise to a sulfinyl enone upon rearrangement [138]. In related work, the addition-elimination of an allyl alkoxide to a functionalized vinyl sulfoxide results in a sulfinyl enol ether that rearranges with loss of sulfenic acid to the unsaturated ester [139-141] (Scheme 21). 

Altenbach used the Michael addition of sodium methyl malonate to allene (206) for a dia-stereoselective spiroannulation to a steroid (equation 72). Or, in imaginative work by Okamura, allenyl sulfoxides were transformed into enantiomerically pure hydrocarbons by pericyclic reactions like electrocyclic ring closure (equation 73) or intramolecular cycloaddition (equation 74). Note that the starting materials (propargylic alcohols) are readily accessible as single enantiomers. 

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