Removing Triphenylphosphine Oxide

Copper Salts:

• Quench rxn w/ sat NH ₄Cl aq solution. stir up to a few hours at r.t. or until the solution becomes a dark blue (indicates complexation).
• Remove aq layer and wash organic a few times with sat. NH ₄Cl aq.
• Isolate crude material as in step 4 above.

Boron Compounds:

A number of boron compounds and residues (for example from hydroboration, allylation, reduction, Suzuki coupling, etc) can be removed by concentrating the reaction mixture repeatedly from MeOH. This process forms (MeO) ₃B, which is volatile.

Removing Tin Byproducts

Metal Salts (from the Merlic Group at UCLA, The Organic Companion)

Many transition metals can be removed by precipitation of the sulfides. Wash with aqueous sodium sulfide. If necessary, adjust pH to create H ₂S.

Some transition metals can be removed by aqueous extraction with tris(hydroxymethyl)phosphine. See: R. H. Grubbs Tetrahedron Lett. 1999 , 40, 4137.

Fieser Workup for Aluminum Hydride Reductions

Titanium:

Quench with Aqueous ammonium chloride, the titanium byproduct will partition into the aqueous layer during workup.

Chromium Oxidations:

1. PCC/PDC: Filter the reaction mixture through a pad of florisil.
2. Jones: Add isopropanol until the reaction turns from orange/red to green: this indicates that the oxidant has been consumed.

m-CPBA:

If reaction is done in refluxing DCE (for example), cool reaction mixture to 0°C to precipitate out all m-CPBA. Then add 10% aqueous solution of Na ₂SO ₄. Two layers form. Separate and extract with DCM. Repeat the addition of Na ₂SO ₄ several times then combine all organic layers, wash with saturated solution of NaHCO ₃, then saturated aqueous solution of NaCl, then dry (MgSO ₄) and evaporate under reduced pressure. If purifying product by FCC, any m-CPBA still present is easily separated as it is UV active, extremely polar and it ends to deposit on column tip during purification. This is easily taken care of as m-CPBA is soluable in EtOAc.

DCC:

Filter the reaction mixture through a medium frit, rinsing with a minimal amount of reaction solvent, then work up. Depending one runs reaction in dioxane, THF, DMF, dichloromethane, etc., but urea is mostly insoluble in most solvents and this is a good way to get rid of it (the rest can be flashed away pretty straightforwardly). If it is too soluble, one can concentrate the reaction mixture first and take it up in ether, then filter and rinse. (contributed by Philippe Rabbat)