Palladium(II) phthalocyanines efficiently promote phosphine-free Sonogashira cross-coupling reaction at room temperature

Abstract

Herein we report that exceptionally simple and inexpensive Pd(II) complexes of phthalocyanines efficiently catalyze direct formation of diphenylacetylenes at ambient conditions with low loading of catalyst (0.5 mol%). Results of this study demonstrate that terminal alkynes reacted mildly with p-substituted aryl bromides at room temperature under Pd and Cu-cocatalysis to give the corresponding phenylacetylenes in yields up to 98%. Also we have examined this catalyst in Sonogashira cross-coupling with aryl chlorides and it was very effective and this reaction at room temperature that there is no examples in recent articles. This protocol represents the first use of palladium phthalocyanine as homogeneous catalyst in the Pd/Cu-promoted Sonogashira reaction. The palladium(II) phthalocyanine complex is significantly more active in Sonogashira cross-coupling between aryl halides and terminal alkynes as compared with traditional catalysts because of absence of palladium black formation through agglomeration of metal particles and deactivation of catalyst.