Chloriminium

Chloriminium, also referred to as chloroiminium, describes a class of reactive, positively charged species in which a chlorine atom is bonded to a carbon atom of an iminium fragment. The core motif is a chlorinated iminium cation that can be represented generically as [Cl–CH=NR2]+ or [Cl–CH=N–R]+, with various substituents on nitrogen. These cations are typically encountered as salts with counterions such as chloride, tetrafluoroborate (BF4−), or hexafluorophosphate (PF6−). They are commonly formed in situ through chlorination of imines or related precursors and are often short-lived due to their electrophilic and reactive nature.

In reactivity, chloriminium ions act as electrophiles at the iminium carbon and can be intercepted by a range of nucleophiles, including enolates, amines, and organometallic reagents, enabling carbon–carbon and carbon–nitrogen bond formations. They are used as key intermediates in organic synthesis for introducing a chloromethyl or chlorinated iminium fragment into molecules, and they can participate in cyclization or rearrangement pathways depending on the substrate and conditions. The chemistry is typically conducted under strictly anhydrous conditions, and the choice of counterion can influence stability and reactivity.

Safety and handling: chloriminium species are typically moisture-sensitive and can release corrosive hydrogen chloride upon hydrolysis; they should be handled in appropriate facilities with good ventilation and protective equipment.

See also: iminium ion, chloroiminium salts.