Substitution that Involves Elimination at Benzene
OCH3
OCH3
Na
Br
NH2
+
NH3 (l), -33 ˚C
NH2
OCH3
OCH3
Br
Na
NH2
+
NH3 (l), -33 ˚C
Na
NaBr
NH2
OCH3
OCH3
NH2
OCH3
+
NH3 (l), -33 ˚C
Br
NaBr
NH2
+
NH2
This reaction goes by an _________________
elimination - addition pathway and
it involves a high-energy intermediate known as benzyne
_______
NaBr
Elimination−Addition (Benzyne) Reactions of Bromoanisole
Isomers with Sodium Amide in Liquid Ammonia
NaNH2 is a very strong base. The elimination
process follows the [E1cb] pathway. [AdN] to
benzyne is favorable because a triple bond in a 6membered ring causes considerable strain.
Published in: John D. Roberts; J. Org. Chem. 2009, 74, 4897-4917.
DOI: 10.1021/jo900641t
Copyright © 2009 American Chemical Society