Reactions Performed in situ after a Swern Oxidation

Reactions Performed in situ after a Swern Oxidation 

Swern oxidations produce the quite unreactive side compounds carbon monoxide, carbon dioxide, dimethyl sulfide and an amine hydrochloride. Therefore, it is very often possible to perform the in situ addition of a nucleophile to the aldehyde or ketone, resulting from the oxidation. This is particularly useful when the aldehyde or ketone is difficult to isolate, because of possessing an unusually high reactivity. 

The highly unstable trimethylsilylformaldehyde is prepared by Swern oxidation at very low temperature. An in situ condensation with a stabilized phosphorane delivers a silylolefin. If the solution of trimethylsilylformaldehyde is allowed to reach 0°C, no condensation product is obtained, which proves that trimethylsilylformaldehyde is not stable in 

The hindered, stabilized Wittig reagent is unable to react with ketones, but reacts slowly with normal unhindered aldehydes at elevated temperature. However, it reacts at a reasonable rate with the highly reactive starting a-ketoaldehyde at 0°C. No reaction occurs on the 

Although many aldehydes with lesser reactivity can be isolated and purified before condensation with phosphorous compounds, often an in situ condensation is performed for experimental convenience.225 

---