# How to convert phenylacetic acid to 3-phenylpropionitrile?

I understand that phenylacetic acid reacts with $$\ce{KSCN}$$ can form phenylacetonitrile plus the side product ($$\ce{CO2}$$ and $$\ce{KSH}$$). This is Letts nitrile synthesis

However, the problem is to convert phenylacetic acid to 3-phenylpropionitrile. Is that possible? What reagents do we need?

You need to add one carbon, the easiest source of this is as CN-.

Three steps.

1. Reduce phenylacetic acid to 2-phenylethanol (borane.THF is a good way)

2. Form the tosylate of the alcohol (TsCl, pyridine)

3. Treat the tosylate with NaCN in DMSO reference here.