Abstract
An unprecedented microwave-assisted palladium-catalyzed reaction
on polymer support with simultaneous cooling has been developed.
It has also been illustrated that under simultaneous cooling, certain
decomposition and side reactions during the reaction, because of
heating, can be minimized.
Key words
2(1H )-pyrazinones - palladium
catalysis - solid support - microwave - simultaneous
cooling
References and Notes
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7 See power profile in Supporting Information.
8 All microwave-irradiation experiments
were carried out in a dedicated CEM-Discover-Coolmate monomode microwave apparatus
(CEM Corporation P.O. Box 200 Matthews, NC 28106), operating at
a frequency of 2.45 GHz with continuous irradiation power from 0-300
W. Reaction mixtures were efficiently stirred with a magnetic stirrer.
The reactions were carried out in an open 10 mL double-walled glass
vial which was cooled to 0-35 ˚C using
a microwave transparent cooling liquid. The temperature of the cooling liquid
was between 15 ˚C and 18 ˚C.
Irradiation and cooling were started simultaneously, starting with
the reaction mixture at r.t. The temperature was measured with a
fiber-optic probe device inserted into the reaction vessel; a schematic
representation of the setup can be found at
9 Experimental details and characterization
data (¹ H NMR, ¹³ C
NMR, and HRMS) of all new compounds are available in the Supporting
Information.
