[65915-25-5] · C11H17O4PS · Diethyl Phenylsulfinylmethylphosphonate · (MW 276.29)
(used for the preparation of vinyl sulfoxides and O,S-acetals of formyl phosphonates)
Physical Data: n
Solubility: sol acetone, MeOH, CH2Cl2, THF.
Preparative Method: most conveniently prepared by controlled oxidation of Diethyl Phenylthiomethylphosphonate (eq 1).1-3
Handling, Storage, and Precautions: diethyl phenylsulfinylmethylphosphonate is reasonably stable for storage. Reactions involving this reagent are best conducted under anhydrous conditions, under nitrogen, in a well ventilated fume hood.
The applications of diethyl phenylsulfinylmethylphosphonate center on its ability to undergo Horner-Emmons and Pummerer reactions.
In the Horner-Emmons reaction, the sulfinylphosphonate can be metalated with n-Butyllithium in THF and then reacted with aldehydes or ketones to form vinyl sulfoxides. For example, this sequence, followed by intramolecular Michael addition, has been used to synthesize chroman sulfoxide, an important intermediate in the synthesis of a-tocopherol (eq 2).4 Modest transfer of chirality from the sulfoxide to the bicyclic product has been observed in this reaction.
Alternatively, the reaction can be conducted under phase transfer conditions, and is then specific for aromatic aldehydes (eq 3).5 Initially a tetraalkylammonium salt was used as catalyst, but it was discovered that the phosphonate could function as its own phase transfer catalyst (eq 3).6 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.7
Diethyl phenylsulfinylmethylphosphonate undergoes the Pummerer reaction under a variety of conditions, resulting in oxidation of the a-carbon with concomitant reduction of the sulfoxide to a sulfide (eq 4).8-11 Limited success in the transfer of chirality from sulfur to carbon has been achieved.10
If the Pummerer reaction is conducted in an aromatic solvent, Freidel-Crafts products are produced (eq 5).11
K. Shankaran & Sherman T. Waddell
Merck Research Laboratories, Rahway, NJ, USA