Sonogashira reaction metals

K. Sonogashira, in Metal-Catalyzed Cross-Coupling Reactions (E. Diederich and P. J. Stang, eds.). Wiley-VCH, Weinheim, 1998. 

For the further decoration of the pyrazinone scaffold via transition metal-catalyzed chemistry, the Sonogashira reaction [45-50] has also been investigated on the C-3 position of the pyrazinone, applying microwave irradiation conditions (Scheme 17) [29]. It was found that microwave irradiation at 120 °C for 15 min of a mixture of the starting material, Pd(OAc)2, Cul and PPha in TEA/DMF were the appropriate reaction conditions. 

The performance of the Sonogashira reaction is claimed to be the first example of a homogeneously metal-catalyzed reaction conducted in a micro reactor [120], Since the reaction involves multi-phase postprocessing which is needed for the separation of products and catalysts, continuous recycling technology is of interest for an efficient production process. Micro flow systems with micro mixers are one way to realize such processing. 

The Sonogashira reaction is a transition metal-catalyzed coupling reaction which is widely used for the preparation of alkyl-, aryl- and diaryl-substituted acetylenes (Table 4.7) [120]. This reaction is a key step in natural product synthesis and is also applied in optical and electronic applications. Sonogashira reactions involve the use of an organic solvent with a stoichiometric portion of a base for capturing the... 

Concerning other metals, Sonogashira coupling products have also been observed in the reaction of Ag(l)-carbenes [133] and Au(I)-supported carbenes [134] in low to moderate yields, but only under harsh conditions (more than 100°C). In this regard, NHC based catalysts for Sonogashira reactions have been supported on different materials that include clays [135], polymers [136] and peptides [137]. 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

Domino transition metal-catalyzed processes can also start with a cross-coupling reaction most often, Suzuki, Stille and Sonogashira reactions are used in this context They can be combined with another Pd-catalyzed transformation, and a number of examples have also been reported where a pericydic reaction, usually a Diels-Alder reaction, follows. An interesting combination is also a Pd-catalyzed borina-tion followed by a Suzuki reaction. 

In triiodoimidazole 21, a selective Suzuki coupling was achieved at C(2), whereas a selective halogen-metal exchange in a diiodoimidazole 23 was realized at C(5). In addition, the Sonogashira reactions of haloimidazoles appear to be very substrate-dependent. 

The Sonogashira reaction of 2-chloropyrazine 1-oxide gave only recovered starting material. Pentylation and octylation of 2-chloropyrazine 1-oxide also failed [9]. Possible explanations for these results were either catalyst agglomeration or metal formation from pyrazinylpalladium... 

The Sonogashira reaction is a C-C coupling reaction of terminal alkynes with aryl or vinyl halides in presence of Pd(0) metal and/or Cu(i) catalyst. These compounds are useful in synthesizing species having pharmaceutical... 

Hierso et al reported a copper-free, Sonogashira reaction for a number of activated and deactivated aryl halides with alkyl-/aryl acetylenes and using a variety of metallic precursors, bases and tertiary phosphanes in [bmim][BF4]. They found that a combination of [Pd(/7 -C3H5)Cl]2/PPh3 with 1 % pyrrolidine in the absence of copper showed the highest activity. 

The SPMs 43 and 44 with opposing 2,2 -bipyridine donor sites for metal complexa-tion were prepared by Schliiter and coworkers using a Sonogashira reaction to effect... 

The coupling of terminal alkynes with aryl or vinyl halides under palladium catalysis is known as the Sonogashira reaction. This catalytic process requires the use of a palladium(0) complex, is performed in the presence of base, and generally uses copper iodide as a co-catalyst. One partner, the aryl or vinyl halide, is the same as in the Stille and Suzuki couplings but the other has hydrogen instead of tin or boron as the metal to be exchanged for palladium. 

The categories of sequentially Pd-catalyzed processes in this chapter are based upon the initial process. These are Heck reactions, allylic substitutions, aminations, Sonogashira couplings, metallations, CH activations, cycloisomer izations and miscellaneous processes. 

Bohm, V. P. W., Herrmann, W. A. Coordination chemistry and mechanisms of metal-catalyzed C-C coupling reactions, 13 a copper-free procedure for the palladium-catalyzed Sonogashira reaction of aryl bromides with terminal alkynes at room temperature. Eur. J. Org. Chem. 2000,3679-3681. 

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