Lionel Spanner
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Registered: 14-12-2021
Location: near Barnsley, UK
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Interesting low-temperature decarboxylation procedure
When reviewing the first syntheses of cubane (Eaton and Pettit, 1964 and 1966), I came across a low-temperature decarboxylation reaction that was used
twice in both, didn't involve the use of heavy metals or highly toxic reagents, and appears to have been forgotten by history.
Put simply, the acid is converted to its t-butyl perester, via the acid chloride, then it's decarboxylated by heating it under reflux in a hydrocarbon
solvent.
I would guess this reaction has remained obscure because it's been superseded by more universal methods such as the Barton decarboxylation.
Now Barton is all well and good if you have pyrithione, AIBN and tributyl tin hydride to hand, but generally speaking, these materials are hard to
find for amateurs. In contrast, t-butyl hydroperoxide is easy to make from t-butyl alcohol, sulphuric acid and hydrogen peroxide.
It's not as flexible as Barton; if the acid forms a relatively stable radical on decarboxylation, e.g. benzyl or allyl, rearrangement products and
dimers will result instead of the intended product, and in the case of allyl radicals, a lot of tar as well. The attached paper by Bartlett and Hiatt
(JACS, 1958) investigated the reaction in considerable detail. Nonetheless, I think it has potential as a useful tool for the amateur organic chemist.
Attachment: low temperature decarboxylation (t-butyl perester).pdf (1MB)
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