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Chapter – 2 Microwave assisted simple and fast…..
2.8 RESULTS AND DISCUSSION
Reactions under dry conditions (i.e., in the absence of a solvent, on a
solid support with or without catalysts) were originally developed in the late
1980s. Synthesis without solvents under microwave irradiation offers several
advantages. The absent of solvent reduces the risk of explosions when the
reaction takes place in a closed vessel in an oven. Moreover, aprotic dipolar
solvents with high boiling points are expensive and difficult to remove from the
reaction mixtures. During microwave induction of reactions under dry
conditions, the reactants adsorbed on the surface of alumina, silica gel, clay,
and others absorb microwaves whereas the support does not, nor does it
restrict the transmission of microwaves. Consequently, such supported
reagents efficiently induce reactions under safe and simple conditions with
domestic microwave ovens instead of specialized expensive commercial
microwave systems.
The N-alkylation of heterocyclic compounds bearing an acidic
hydrogen atom attached to nitrogen is generally accomplished by treatment of
these compounds with an appropriate base followed by treatment of the
resulting salts with an alkylating agent.
In this chapter, dry conditions have been used in the synthesis of all
the organic compounds. Anhydrous potassium carbonate was used as a solid
support and as a basic media too. Dimethylformamide was used in very little
amount to make a slurry at room temperature which has not been considered
as a solvent. Household microwave oven (LG MS-192 W) was used as a
microwave source operating range of 800 W. All the reactions were carried
out at 480 W for desired time.
There are so many reported methods in the literature for the Nalkylation
conventionally as well as microwave induced. Conventional
methods are having tedious work up and purification procedures and are time
consuming while microwave assisted methods are straight forward, fast, time
Department of Chemistry, Saurashtra University, Rajkot – 360 005 102