The Gabriel-Colman rearrangement reaction involves the rearrangement of saccharin or phthalimido ester with a strong base such as an alkoxide to form substituted isoquinolines. This is a ring expansion reaction that requires the nitrogen atom to abstract an enolizable hydrogen to form a carbanion that closes the ring. The displacement of the alkoxide is analogous to the Dieckman condensation, resulting in ring closure. The carbonyl groups on the ring can tautomerize between keto and enol forms, and the amide can tautomerize to an imidic acid form.

1. BY
Dr. Gurumeet.C.Wadhawa
DEPARTMENT OF CHEMISTRY
K. B. P. College,Vashi,Navimumbai
Gabriel–Colman Rearrangement

2. The Gabriel-Colman rearrangement reaction of saccharin or phthalimido
ester with strong base such as an alkoxide to form substituted isoquinolines. In
this rearrangement a ring expansion is seen to be general if there is enolizable
hydrogen on the group attached to the nitrogen. It is necessary for the nitrogen
to abstraction to abstract hydrogen to form the carbanion that will close the
ring.

5. The displacement of the alkoxide is analogous to the displacement
seen in
the Dieckman condensation as it is also a result of a ring closure. The
tautomerization can occur on both of the carbonyl group on the ring
with
interconversion of the keto form to the enol form and the amide form
to
the imidic acid form.

7. References
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13581368.
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