Oxidation of alcohols

The solution comprising DMSO and oxalyl chloride, followed by quenching with triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.^[8][9][10]

Synthesis of acyl chlorides

Oxalyl chloride is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acyl chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent degrades into volatile side products in this application, which simplifies workup. One of the minor byproducts from the N,N-dimethylformamide catalyzed reaction, dimethylcarbamoyl chloride, is a potent carcinogen, stemming from the N,N-dimethylformamide decomposition.^[11][12] Relative to thionyl chloride, oxalyl chloride tends to be a milder, more selective reagent. It is also more expensive than thionyl chloride so it tends to be used on a smaller scale.

This reaction involves conversion of N,N-dimethylformamide to the imidoyl chloride derivative (chloromethylene(dimethyl)ammonium ion (CH₃)₂N⁺=CHCl), akin to the first stage in the Vilsmeier–Haack reaction. The imidoyl chloride is the active chlorinating agent.

Formylation of arenes

Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation.^[13][14] The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.

Preparation of oxalate diesters

Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:

2 R−CH₂−OH + Cl−C(=O)−C(=O)Cl → R−CH₂−O−C(=O)−C(=O)−O−CH₂−R + 2 HCl

Typically, such reactions are conducted in the presence of a base such as pyridine. The diester derived from phenol, phenyl oxalate ester, is Cyalume, the active ingredient in glow sticks.

Other

Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketone (C₄O₆), an oxide of carbon.^[15]