# Decarboxylation product of bicyclic compound

What is the decarboxylation product of the following species:

It may seem straightforward but the product enolate involves a double bond with one end at the bridgehead carbon which is impossible/very unstable. What is the correct product and how is the product reached mechanistically.

• Could the resulting enol tautomerize? – Lighthart Apr 8 '15 at 17:26
• Yes it could. But the enolate must surely form initially? – RobChem Apr 8 '15 at 17:27
• Enolization is a blindingly fast reaction. Even though the intermediate is unstable, the easy pathway forward might allow formation of the resulting ketone, despite the bridgehead. – Lighthart Apr 8 '15 at 17:38

${\beta}$-keto acids typically decarboxylate very smoothly at temperatures between 100-200°C. The mechanism involves a cyclic, 6-membered transition state that first produces an enol intermediate (see figure).
However in the case of your bicyclo[2.2.1] ${\beta}$-keto acid, a bridgehead double bond would result. As you correctly point out, such a structure would be very high energy. Therefore this compound does not decarboxylate at normal temperatures (reference, see p. 218, scheme 6.53).