# Reagents in Krapcho's decarboxylation

Krapcho's decarboxylation is a reaction involving esters with a electron-withdrawing group $$\beta$$ to the carbonyl group and halide ions. It is typically conducted with $$\ce {LiCl}$$ and $$\ce {DMSO}$$ at high temperatures. However, in one of Krapcho's original papers, $$\ce {NaCN}$$ was also used alongside $$\ce {DMSO}$$.

What interests me is the first step of the reaction which involves the nucleophilic subsitution, likely by an $$\ce {S_N2}$$ pathway, of the alkyl group of the ester functionality. This is seemingly weird as the $$\ce {C-O}$$ bond usually does not break unless in acid catalysis. This is the case for the cleavage of ethers using $$\ce {HX}$$. I suppose the use of $$\ce {LiCl}$$ was to allow the $$\ce {Li^+}$$ to coordinate to the oxygen atom, allowing the $$\ce {C-O}$$ bond to cleave more easily. Why is it that $$\ce {NaCN}$$ can also do the job?

• CN- is much stronger nucleophile. – Mithoron Feb 17 at 20:50