It is true that DMSO has no known azeotropes. This and its high boiling point account for the difficulty of removing it from reaction mixtures.
It is not true that DMSO is difficult to dry. DMSO distilled under vacuum after taking a forerun is water-free.
Whatever its disadvantages DMSO is too valuable a solvent to rule it out.
DMSO is reported to be immiscible with cyclohexane, heptane, hexane, pentane, 2,2,4-trimethylpentane, and diethyl ether, so these liquids can be used in solvent/solvent extractions. Silylation of the solutes in a reaction mixture should improve their extraction into these less polar solvents which can provide a second layer with DMSO.
DMSO is reported to be miscible with methyl t-butyl ether (MTBE). Based on the reported immiscibility with diethyl ether, this would not necessarily be expected. Perhaps adding a small amount of hydrocarbon to the MTBE could provide a two-phase mixture. An anhydrous DMSO produces a phase separation with diisopropyl ether (DIPE) according to the “Solvent of the Week” website. This would permit more flexible liquid/liquid extractions to separate a product from DMSO.
Another potential way to work up reactions done in DMSO could be to concentrate the solution as much as possible under vacuum, and then add the minimum stirrable volume of glycerol (enough to still provide some slight agitation even if the DMSO gets completely removed) and displace the remaining DMSO, still operating under vacuum. Then, any suitable solvent that is immiscible with glycerol (there are many) could be added and the substrates of interest taken into it. Mixtures of solvents both immiscible with glycerol can be used to increase the extraction’s effectiveness.
Paraffin can also be used instead of glycerol as the chaser for DMSO and this could be useful if the substrate you are trying to recover is polar. Then, extraction from paraffin into lower alcohols becomes possible since these alcohols will be immiscible with the saturated hydrocarbon (paraffin) medium.
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