Abstract
An efficient procedure for C–P bond formation via the palladium-catalyzed [Pd(OAc)2/dppf/Cs2CO3] reaction between dichloroheterocycles and secondary phosphine oxides was developed.
The steric and electronic properties of substituents were varied to establish the
scope and limitations of the method developed. By applying these conditions, a variety
of new heterocyclic compounds bearing two tertiary phosphine oxides were successfully
synthesized in moderate to excellent yields. After adjustments to the reaction conditions
[Pd(OAc)2/dippf/t-BuOK], cross-coupling of secondary phosphine oxides with bulky (secondary or tertiary
alkyl) substituents on the phosphorus atom was achieved. Extension of the methodology
to monohalohetarenes and monohaloarenes was successfully carried out; once again,
the steric and electronic properties of the halides were varied widely. The desired
reaction occurred in all cases studied, giving high to excellent yields of product
regardless of the nature and positions of substituents.
Key words
cross-coupling - palladium - phosphine oxides - heterocycles - homogeneous catalysis
