Methyl cyanoformate is the organic compound with the formula CH<sub>3</sub>OC(O)CN. It is used as a reagent in organic synthesis as a source of the methoxycarbonyl group, in which context it is also known as Mander's reagent. When a lithium enolate is generated in diethyl ether or methyl t-butyl ether, treatment with Mander's reagent will selectively afford the C-acylation product. Thus, for enolate acylation reactions in which C- vs. O-selectivity is a concern, methyl cyanoformate is often used in place of more common acylation reagent like methyl chloroformate.
Methyl cyanoformate is also an ingredient in Zyklon B. It has lachrymatory effects.