C O M M U N I C A T I O N S
Table 2. Catalytic Transamidation of N-Alkyl Heptanamide with
Table 3. Catalytic Transamidation of N-Aryl Amides with Aryl
Primary Alkyl Aminesa
Aminesa
a Reaction conditions: amine (0.33 mmol), amide (0.33 mmol), catalyst
(0.033 mmol), 2 mL of p-xylene, 120 °C, 20 h. b Determined by GC (internal
standard ) triphenylmethane). The starting materials and products shown
are the only species observed.
a Reaction conditions: amine (0.33 mmol), amide (0.33 mmol), catalyst
(0.017 mmol), 2 mL of toluene, 90 °C, 20 h. b Determined by GC (internal
standard ) triphenylmethane) and 1H NMR. The starting materials and
products shown are the only species observed by these methods.
anions suggest that a bifunctional pathway may be crucial for
effective catalysis.
The substrate-dependent variations in catalytic activity that
emerge from our results (cf. alkyl vs arylamide substrates) are
intriguing because they suggest that it might be possible to develop
catalysts with functional group selectivity. Elucidation of the
mechanistic principles underlying these novel transamidation reac-
tions is a focus of our ongoing work and should enable the
development of new equilibration catalysts with even greater activity
and selectivity. Catalysts spawned by these studies will be applied
to equilibrium-controlled syntheses of new amide-based molecules
and materials.
Figure 2. Representative time-course data (GC) for the Al2(NMe2)6-
catalyzed equilibrium exchange between N-benzyl heptanamide/isoamyl-
amine, forward, and N-isoamyl heptanamide/benzylamine, reverse (see entry
2, Table 2).
Acknowledgment. This research was supported by the NSF
(CHE 014062 to S.H.G.) and a seed grant from the MRSEC at
UW-Madison (to S.S.S. and S.H.G.).
previously successful scandium and titanium complexes (Figure 1)
are not effective catalysts for the N-alkyl amide exchange reactions
(Table 2).
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Equilibrium transamidation can be achieved between anilines and
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are required (Table 3). Both metal amide complexes (Ti and Al)
display activity; however, in this case, the titanium catalyst is more
effective. Sc(OTf)3 fails to promote these nearly thermoneutral
reactions, as seen previously with the alkylamine/N-alkyl amide
reactions.
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