Gabriel–Colman rearrangement

The Gabriel–Colman rearrangement[1] is the chemical reaction of a saccharin or phthalimido ester with a strong base, such as an alkoxide, to form substituted isoquinolines.

The reaction mechanism[5][6] starts with an attack on the carbonyl group by a strong base, such as methoxide ion.

This is facilitated by the electron withdrawing effect of the substituent, which allows for greater stabilization of the adjacent carbanion with respect to the imide anion.

The major application of the Gabriel–Colman rearrangement is in the formation of isoquinolines, due to the relatively high yield of the desired products.

[7] It has also been used in the study of phthalimide and saccharin derivatives as mechanism based inhibitors for three enzymes; the human leukocyte elastase, cathepsin G and proteinase 3.