Sonogashira coupling reaction copper-free

A copper-free Sonogashira coupling reaction in ionic liquids and its application to a microflow system for efficient catalyst recycling, Org. Lett. 4, 10 (2002) 1691-1694. 

Scheme 7.2 Copper-free Sonogashira coupling reaction in supercritical water...

Liang B, Dai M et al (2005) Copper-free Sonogashira coupling reaction with PdCl in water under aerobic conditions. J Org Chem 70 391-393... 

Fukuyama, T., Shinmen, M., Nishitani, S., Sato, M. Ryu, I. (2002). A Copper-Free Sonogashira Coupling Reaction in Ionic Liquids and Its Application to a Microflow System for Efficient Catayst Recycling, Org. lett., 4, p>p. 1691-1694... 

In copper-free Sonogashira coupling the competition of ligand and amine base determines the reaction mechanism. The oxidative addition of Arl with (Ph3P)4Pd is faster when amine is present. With the proposed mechanisms the efficiency of PhsP > PhsAs is explained. 

Miura et al. reported the first palladium-free Sonogashira coupling reaction of aryl iodides or vinyl iodides with terminal allqmes in the presence of a copper iodide/triphenylphosphine/potassium carbonate catalyst system (Scheme 15.14). o-Iodo-acetanilide derivatives react with l-allg nes smoothly even at room temperature in the presence of a copper iodide/AT-methylpyrrolidine-2-carboxamide catalyst system (Scheme Various... 

Sonogashira Couplings Investigated in Micro Reactors Organic synthesis 46 [OS 46) Copper-free Son<%ashira reaction... 

McLaughlin and co-workers have described a one-pot copper-free Sonogashira alkynylation and base-mediated indolization reaction to access 1,2-disubstituted indoles 125 and azaindoles from o-chloroanilines 123 <060L3307>. A ligand-, copper, and amine-free variant of the Sonogashira coupling was used by Srinivasan and co-workers to access 2-substituded indoles <06T5109>. 

Generally, the Sonogashira coupling reaction is achieved by a palladium-copper catalyzed reaction of aryl or vinyl halide and terminal alkyne [70-72], The presence of the copper co-catalyst is an obstacle, however, towards the metallodendritic approach of the system. In this context, only a few examples of copper-free procedures have been reported [73-77], involving for instance, in situ Pd(0) complex formation with bulky phosphines [78]. 

The dendrimers 23a-c were used in a copper-free Sonogashira-type coupling reaction between phenylacetylene and iodobenzene or bromobenzene. The catalyst amount was 1 mol % per catalytic group (i.e., 1/4, 1/8 and 1/16 mol% depending on the dendrimer generation generations 1, 2 and 3), and the temperature range was 25-120 °C. 

A, A -dimethylaniline group has been synthesized by a copper-free Sonogashira cross-coupling reaction using microwave irradiation as the source of energy <2006EJO2344>. The electrochemical and photophysical properties of the triad were systematically investigated by techniques such as time-resolved fluorescence and transient absorption spectroscopy. 

The Sonogashira coupling reaction of terminal alkynes with aryl or vinyl halides is a useful tool for carbon—carbon bond formation, and has found wide employment in areas such as natural product synthesis, the pharmaceutical industry, and material sciences. Novel recyclable Pd catalysts with fluorous ponytails in the ligand 2,2 -bipyridine were reported in a copper-free Pd-catalyzed Sonogashira reaction in a fluorous biphasic system (FBS) (Equation 4.19). The catalysts are only soluble in perfluorinated solvents at room temperature [41],... 

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