The Kowalski ester homologation is a chemical reaction for the homologation of esters.
This reaction was designed as a safer alternative to the Arndt–Eistert synthesis, avoiding the need for diazomethane. The Kowalski reaction is named after its inventor, Conrad J. Kowalski.
The mechanism is disputed.
By changing the reagent in the second step of the reaction, the Kowalski ester homologation can also be used for the preparation of silyl ynol ethers.