characteristic of enamines, the enamine moiety of complex 34 undergoes C–C bond
formation with the α,β-unsaturated carbonyl compound, forming a bound imine (35,
36), which undergoes C–C rupture, generating the Michael-addition product and
complex 32. It is noteworthy that Michael addition of simple nitriles to α,β-unsaturated carbonyl compound normally requires a strong base and elevated
temperatures.
Utilizing the tool of MLC by dearomatization/aromatization, Otten and de Vries
reported the useful oxa-Michael addition reaction of alcohols to unsaturated nitriles
using a dearomatized Ru-PNN complex under mild conditions [83]. However, much
lower yield was observed for the corresponding aza-Michael addition reactions of
amines with unsaturated nitriles even at longer reaction time and at higher temperatures. We have recently discovered that the analogous dearomatized Mn-PNN
complex 3 can catalyse both oxa- and aza-Michael addition reactions under mild
Table 3 Substrate scope of oxa- and aza-Michael addition of unsaturated nitriles
Reaction conditions: crotononitrile or 2-pentenenitrile (2.0 mmol), alcohol or amine (2.0 mL),
complex 3 (0.0020 mmol, 0.1 mol%), r.t., 24 h. Yields determined by
1
H NMR with mesitylene as
the internal standard
a Isolated yields
b
0.5 mol% complex 3 was used
c Benzylamine (1.0 mL) was used
Recent Advances in the Applications of Metal-Ligand Cooperation via. . .
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