Halogeneerimine

Halogeneerimine is a term used in chemistry to describe halogenation reactions that introduce a halogen atom into a substrate, with a focus on reactions at nitrogen-containing centers. In organic synthesis, two common variants are distinguished: N-haloation of amines to give N-haloamines and halogenation of imines to form N-haloimines.

N-haloamines are typically formed by treating amines with electrophilic halogen sources such as chlorine or bromine, or milder reagents like N-chloro- or N-bromo-succinimide (NCS, NBS). Primary and secondary amines can be converted to N-haloamines, though primary amines often yield less stable intermediates that may undergo further transformations. N-haloamines can serve as reactive intermediates in sequences such as rearrangements, oxidations, or subsequent substitutions to access a range of nitrogen-containing products.

N-haloimines arise when halogenation occurs at the nitrogen of an imine, producing species of the form R2C=NR–X. These compounds act as electrophilic partners in various synthetic transformations, including cycloadditions and additions to imines, and can be used to activate nitrogen for subsequent bond-forming steps.

Reagent selection and reaction conditions influence selectivity and outcome. Typical halogen sources include Cl2, Br2, I2, and NCS/NBS/NIS, chosen based on substrate sensitivity and desired degree of halogenation. Safety considerations are important due to the corrosive and oxidizing nature of halogens and hypohalous species. Halogeneerimine methods are valued for their ability to install halogen functionality that can direct downstream chemistry in the synthesis of complex molecules.