The synthesis of isocyanates from amines illustrates the electrophilic character of this reagent and its use in introducing the equivalent synthon "CO":
:, where R = alkyl, aryl
Such reactions are conducted on laboratory scale in the presence of a base such as pyridine that neutralizes the hydrogen chloride side-product.
Phosgene is used to produce chloroformates such as benzyl chloroformate:
In these syntheses, phosgene is used in excess to prevent formation of the corresponding carbonate ester.
With amino acids, phosgene (or its trimer) reacts to give amino acid N-carboxyanhydrides. More generally, phosgene acts to link two nucleophiles by a carbonyl group. For this purpose, alternatives to phosgene such as carbonyldiimidazole (CDI) are safer, albeit expensive. CDI itself is prepared by reacting phosgene with imidazole.
Phosgene is stored in metal cylinders. In the US, the cylinder valve outlet is a tapered thread known as "CGA 160" that is used only for phosgene.