Diethyl methylthiomethylphosphonate

Reaction of l,3-bis(methylthio)-2-methoxypropane with 2 moles of lithium diisopropylamide5 (or w-butyllithium) effects (a) the elimination of methanol to form l,3-bis(methylthio)propene and (b) the lithiation of this propene to generate l,3-bis(methylthio)allyllithium in solution. Its conjugate acid, l,3-bis(methylthio)propene, can be regenerated by protonation with methanol, and has also been prepared (a) in 31% yield by reaction of methylthioacetaldehyde with the lithio derivative of diethyl methylthiomethylphosphonate,5 (b) in low yield by acid-catalyzed pyrolysis of l,l-bis(methylthio)-3-methoxypropane,6 and (c) in low yield by acid-catalyzed coupling of vinyl chloride with chloromethyl methyl sulfide.7... 

The reagent is prepared from diethyl methylthiomethylphosphonate (3, 97) by trcatmeni with n-butyllithium under argon at —78° followed by addition of methyl iodide (yield 77 %). 

KETONES Dicobalt octacarbonyl. Diethyl methylthiomethylphosphonate. 2,4,4,6-Tetramethyl-5,6-dihydro-l, 3-(4H)-oxazine. 

Diethyl methylthiomethylphosphonate can be alkylated by successive treatment with n-butyl-lithium and an alkyl iodide the lithio-derivatives of such alkylated esters react with carbonyl compounds to give /S-alkoxyphosphonate adducts. These products decompose readily to vinyl methyl sulphides, which undergo mercury(ii)-promoted hydrolysis to the corresponding ketone. These transformations are outlined in Scheme 53. 

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