10
Sanchez et al.
|
product was dissolved in 85 mL warm water and upon cool-
ing to room temperature crystals formed, which were col-
lected and recrystallized from boiling water (yield, 18%).
The heteropolyanion was converted to its corresponding
acid H14[NaP5W30MoO110] (HPA) by passing an aqueous
solution of HPAMoK through a Dowex-50Wx8 ion-exchange
column. The catalyst was properly characterized.
test, the catalyst was separated from the reaction mixture by
filtration, washed with toluene (2 × 2 mL), dried under vac-
uum, and then reused.
4.7
Green metrics
|
In order to quantify the sustainability for the methodology
presented, various green metric parameters were calculated
for each reaction performed. Thus, relevant quantitative
factors such as atom economy (AE), atomic efficiency fac-
tor (E), process mass intensity (PMI), and semiquantitative
EcoScale were determined.
4.3.
General procedure for the preparation
|
of dihydropyrimidinones (thiones)
The solid catalyst (0.5 mmol %) was added to a mixture of
3-formylchromones (1 mmol), 1,3-dicarbonyl compounds
(1 mmol), and urea or thiourea (1.5 mmol). The mixture was
stirred at 80°C for 90 min. The progress of the reaction was
monitored by TLC. After completion of the reaction, hot tolu-
ene was added (2 × 2.5 mL) and the catalyst was filtered. The
extracts were combined dried with anhydrous sodium sulfate,
and the solvents concentrated in vacuum. All the solid crude
products were recrystallized (Compounds 1–6).
ACKNOWLEDGMENTS
We thank Universidad Nacional de La Plata (UNLP),
CONICET (PIP 003) and ANPCyT (PICT 0409) for financial
support. A. S. and G. R. are members of CONICET.
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4.4.
General procedure for the
|
preparation of 1,4-dihydropyridines
The solid catalyst (0.5 mmol %) was added to a mixture of
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4.5.
General procedure for the
|
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4.6.
Catalyst reuse
|
Stability tests of the Preyssler catalysts were carried out by
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