Koenigs-Knorr reaction

The Koenigs-Knorr reaction in organic chemistry is the substitution reaction of a glycosyl halide with an alcohol to give a glycoside. It is one of the oldest and simplest glycosylation reactions. It is named after William Koenigs (1851-1906), student of von Bayer and fellow student with Emil Fischer, and Edward Knorr, student of Koenigs.

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In its original form, Koenigs and Knorr treated acetobromoglucose with alcohols in the presence of silver carbonate.^[1] Shortly afterwards Fischer and Armstrong reported very similar findings.^[2]

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.

The Koenigs-Knorr reaction can be performed with alternative promoters such as various heavy metal salts including mercuric bromide/mercuric oxide, mercuric cyanide and silver triflate.^[3][4]

References

1. ^ Koenigs, W. and Knorr, E. (1901) Ber. Dtsch. Chem. Ges., 34, 957
2. ^ Fischer, E. and Armstrong, E.F. (1901) Ber. Dtsch. Chem. Ges., 34, 2885
3. ^ Helferich, B. and Zirner, J. (1962) Chem. Ber., 95, 2604
4. ^ Hanessian, S. and Banoub, J. (1980) Methods Carbohydr. Chem., 8, 247