In its original form, Koenigs and Knorr treated acetobromoglucose with alcohols in the presence of silver carbonate. Shortly afterwards Fischer and Armstrong reported very similar findings.
In the above example, the stereochemical outcome is determined by the presence of the neighboring group at C2 that lends anchimeric assistance, resulting in the formation of a 1,2-trans stereochemical arrangement. Esters generally provide good anchimeric assistance, whereas ethers (eg benzyl, methyl etc) do not, leading to mixtures of stereoisomers.
Generally, the Koenigs–Knorr reaction refers to the use of glycosyl chlorides, bromides and more recently iodides as glycosyl donors.