3-Thiolene 1,1-dioxide (I) adds various nucleophiles such as ammonia, amines, alcohols, thiols, and CH-acids to give functionalized sulfolanes, which are active complexing solvents and hold promise as synthones and intermediates [1]. However, there is only l~ited information on the reaction of thiolene I with PH-acids. Bezmenova [1] and McConnell [2] briefly reportcd the nucleophilic and radical addition of dialkyl phosphites to this compound. Recently, we reported that a secondary phosphine oxide, namely, bis(2-pl~enylethyl)phosphine oxide, may add to thiolene I [3].In order to obtain further information on the reactivity of unsaturated cyclic sulfones and develop a convenient synthesis for highly polar nonhydroxyl solvents combining the unique properties of sulfolane and organic phosphine oxides in a single molecule, we studied the reaction of thiolene I with 2-phenylethylphosphine, bis(2-pbenylethyl)phosphine, bis(2-phenylethyl)phosphine oxide, and bis(2-phenylpropyl)phosphine oxide, which are readily obtained from red phosphorus or phosphine, styrene, and ~-methylstyrene [4]. In this work, we also checked the feasibility of the reaction of thiolene I with phosphorus nucleophiles generated directly from red phosphorus and phosphine in the presence of strong bases.Thiolene I reacts with a stoiehiometric amount of 2-phenylethylphosphine (II) upon heating to 35-40~ for 5 h in a KOH-DMSO superbase system [5] to give bis(3-thioanil)(2-phenylethyl)phosphine oxide (IV) in 40% yield. The expected product, bis(3-t.hioanil)(2-phenylethyl)phosphine OH) was not identified in the reaction mixture, probably due to its high tendency to undergo oxidation, which could not be prevented even by carrying out the reaction in an inert gas atmosphere. The oxidation agent in this case may not only be atmospheric oxygen but also DMSO. Since the nucleophilic addition reaction is not typical for allylsulfones, thiolene I tipon phosphorylation in the KOH-DMSO system apparently initially undergoes prototropic isomerization to give 2-thiolene 1,1-dioxide with a highly electrophilic double bond.
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