Palladium in Heterocyclic Chemistry 27It is also possible to use an organometallic, giving a ketone, but careful choice of partner is required to avoid competi-
tive cross coupling.
Cross-coupling reactions between heteroatom nucleophiles
and halides – making carbon–heteroatom bonds
Heteroatom nucleophiles bearing an ‘acidic’ hydrogen, in the presence of a base, or as a preformed metal derivative, can
be used in palladium(0)-catalysed processes to make carbon–heteroatom bonds. Cross-couplings with nitrogen, sulfur
and oxygen nucleophiles (amine, thiol and alcohol/phenol) work well. Heterocyclic N-hydrogen can also be substituted
using palladium catalysis, though there are many more examples using copper (page 30).
Tr i fl ates as substrates for palladium-catalysed reactions
Tr i fl ates (trifl uoromethanesulfonates: Ar-OSO 2 CF 3 ) give comparable reactions to bromides and are very useful for
activating phenols when the corresponding aryl halide is not available. In the context of this book, they can also be used
to activate - and -hydroxy-heterocycles that usually exist as carbonyl tautomers, for example oxindoles, pyridones
and furanones.