Copper-free Sonogashira cross-coupling reactions: an overview

The Sonogashira reaction is a cross-coupling reaction of a vinyl or aryl halide with a terminal alkyne to form a C-C bond. In its original form, the Sonogashira reaction is performed with a palladium species as a catalyst while co-catalyzed by a copper species and a phosphine or amine. The reaction is conducted under mild conditions, i.e., room temperature, aqueous solutions, and the presence of mild bases. Undeniably, the Sonogashira reaction is among the most competent and efficient reactions widely used in organic synthesis. This named reaction has proved useful in many organic synthesis areas, including the synthesis of pharmaceuticals, heterocycles, natural products, organic compounds, complex molecules having biological activities, nanomaterials, and many more materials that we use in our daily lives. The presence of transition metals as a catalyst was indeed essential in the Sonogashira reaction. However, recently, the reaction has been successfully conducted without copper as a co-catalyst and phosphines or amines as bases. In this critical review, we have focused on developments in the Sonogashira reaction successfully performed in the absence of copper complexes, phosphines or amines, which could be of particular advantage in implementing green chemistry principles and making the reactions more achievable from an economic viewpoint.

Coordination Self-Assembly Processes Revealed by Collaboration of Experiment and Theory: Toward Kinetic Control of Molecular Self-Assembly

The importance of the collaboration of experiment and theory has been proven in many examples in science and technology. Here, such a new example is shown in the investigation of molecular self-assembly process, which is a complicated multi-step chemical reaction occurring in the reaction network composed of a huge number of intermediates. An experimental method, QASAP (quantitative analysis of self-assembly process), developed by us and a numerical approach, NASAP (numerical analysis of self-assembly process), that analyzes the experimental data obtained by QASAP to draw detail molecular self-assembly pathways, which was also developed by us, are introduced, and their application to the investigation of Pd(II)-mediated coordination assemblies are presented. Further, the possibility of the prediction of the outcomes of molecular self-assembly by varying the reaction conditions is also demonstrated. Finally, a future direction in the field of artificial molecular self-assembly based on pathway-dependent self-assembly, that is, kinetic control of molecular self-assembly is discussed.

Phosphinito palladium(ii) complexes as catalysts for the synthesis of 1,3-enynes, aromatic alkynes and ynones

An air-stable phosphinito palladium(ii) complex has been found to be an efficient catalyst in the formation of C–C bonds.