[50746-61-7] · C6H15O4PS · Diethyl Methylsulfinylmethylphosphonate · (MW 214.22)
(used for the preparation of vinyl sulfoxides and O,S-acetals of formyl phosphonates)
Physical Data: n
Solubility: sol acetone, CH2Cl2, MeOH, THF.
Preparative Methods: diethyl methylsulfinylmethylphosphonate can be obtained by controlled oxidation of Diethyl Methylthiomethylphosphonate, as shown in eq 1.1-4 The procedure using Br2/aq. NaHCO3/CH2Cl2 is notable because use of H218O allows for the preparation of 18O sulfoxides.2
Handling, Storage, and Precautions: Diethyl methylsulfinylmethylphosphonate is reasonably stable for storage. Reactions involving this reagent are best conducted under anhydrous conditions, under nitrogen, in a well ventilated fume hood.
The sulfinylmethylphosphonate can be metalated with n-Butyllithium in THF and then reacted with a variety of aldehydes and ketones to form vinyl sulfoxides via the Horner-Emmons reaction (eq 2).5 Alternatively, the reaction can be conducted under phase transfer conditions, and is then specific for aromatic aldehydes.6 Initially a tetraalkylammonium salt was used as catalyst, but it was discovered that the phosphonate could function as its own phase transfer catalyst.7 Subsequent reports showed that it can function generally as a phase transfer catalyst, for example in the alkylation of benzyl methyl ketone with butyl bromide.8
Diethyl methylsulfinylmethylphosphonate undergoes the Pummerer reaction, resulting in oxidation of the a-carbon with concomitant reduction of the sulfoxide to a sulfide (eq 3).9-12 Limited success in the transfer of chirality from sulfur to carbon has been achieved.11
If the Pummerer reaction is conducted in an aromatic solvent, Freidel-Craft products are produced (eq 4).12,13 In a similar manner, treatment of Pummerer products with alkenes gives ene style products (eq 5).14
K. Shankaran & Sherman T. Waddell
Merck Research Laboratories, Rahway, NJ, USA