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E. Mas-Marza´ et al. / Tetrahedron Letters 44 (2003) 6595–6599
Acknowledgements
Cs2CO3 as the base, and we conclude that activity
was highest with piperidine13 (Table 2, entries 1, 7
and 9). Before validating the concept of effective cat-
alyst recycling, we selected an appropriate solvent to
simplify the protocol of washing the solid catalyst
system after it has been separated from the products
via filtration. Therefore, we demonstrated that the use
of DMA (N,N-dimethylacetamide) as solvent could
be a convenient medium for efficient catalyses and for
removing all the products and ammonium salts
involved in the reaction, from [PdBr(CNC-Me2)]Br/
clay (Table 2, entries 8–14). Catalyst recycling studies
were carried out after [PdBr(CNC-Me2)]Br/clay had
been recovered, and washed with DMA and CH2Cl2.
Pd-black deposit was not observed in the washed
solid, confirming the great stability of the catalyst
when is immobilized. The resulted recovered solids
could be successfully reused showing the same activity
as for the first run in the coupling of phenylacetylene
and phenyliodide (Fig. 3, a: [PdBr(CNC-Me2)]Br/
MK10, b: [PdBr(CNC-Me2)]Br/BA and c: [PdBr-
(CNC-Me2)]Br/BB).
This work was supported by DGES(BQU2001-0656),
PSR(N-2002PSR55), (MAT2002-04421-C02-01) and
MECD for fellowship (E.M.-M.).
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