Zusammenfassung
The transfer of simple alkyl groups in
Stille reactions usually requires special solvents
(HMPA) or certain organotin reagents (stannatranes,
monoorganotin halides) to be efficient.
Using low-melting mixtures of sugar, urea and inorganic
salt as solvent, a fast and efficient palladiumcatalyzed
alkyl transfer with tetraalkyltin reagents
was observed. The high polarity and nucleophilic
character of ...
Zusammenfassung
The transfer of simple alkyl groups in
Stille reactions usually requires special solvents
(HMPA) or certain organotin reagents (stannatranes,
monoorganotin halides) to be efficient.
Using low-melting mixtures of sugar, urea and inorganic
salt as solvent, a fast and efficient palladiumcatalyzed
alkyl transfer with tetraalkyltin reagents
was observed. The high polarity and nucleophilic
character of the solvent melt promotes the reaction.
Stille biaryl synthesis using electron-poor and electron-
rich aryl bromides proceeds with quantitative
yields in the sugar-urea-salt melt. Catalyst loading
may be reduced to 0.001 mol% and the catalyst
melt mixture remains active in several reaction
cycles. Showing the same or improved performance
for Stille reactions than organic solvents and allowing
a very simple work up, sugar-urea-salt melts are
a non-toxic and cheap alternative reaction medium
available in bulk quantities for the catalytic process.
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