Phenacaine

Phenacaine, also known as holocaine, is a local anesthetic. It is approved for ophthalmic use.

Synthesis
The synthesis of phenacaine begins with the condensation of p-phenetidine (1) with triethyl orthoacetate (2) to afford the imino ether (a Pinner salt, 3). Reaction of that intermediate with a second equivalent of the aniline results (4) in a net displacement of ethanol, probably by an addition-elimination scheme, producing the amidine, phenacaine (5).



In the patented synthesis, phenacetin was used as precursor. Treatment with phosphorus trichloride (PCl3) gave the enol chloride, and reaction of this intermediate with p-phenetidine then completed the synthesis of phenacaine.