New coupling partners

Historically, one of the most important limitations of the Suzuki-Miyaura reaction was the poor reactivity of organic chlorides, attributed to the strength of the C-Cl bond. Aryl chlorides are very attractive halides due to their low cost and wider diversity of available compounds. Prior to 1998, reports of effective palladium-catalyzed Suzuki reactions of aryl chlorides were limited to activated substrates, and generally employing very high temperatures. In that year. 

In addition to the already generalized couplings of aryl iodides, bromides, and chlorides, in 2003, the coupling of activated fluorides with boronic acids was reported (Table 2, entry The coupling with pseudohalogens has 

2 OTf Aryl, alkenyl, alkyl Aryl, alkenyl, alkyl 

Other pseudohalides such as aryldiazonium ions (Table 2, entry arylsulfonyl chlorides (Table 2, entry 4),  

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Kirchhoff, J. H., Netherton, M. R., Hills, I. D., Fu, G. C. Boronic Acids New Coupling Partners in Room-Temperature Suzuki Reactions of Alkyl Bromides. Crystallographic Characterization of an Oxidative-Addition Adduct Generated under Remarkably Mild Conditions. J. Am. Chem. Soc. 2002, 124, 13662-13663. 

The scope of the SH reaction encompasses sp-sp2 (alkenyl, aryl (29),143 heteroaryl) and sp-sp couplings (the modified Cadiot-Chodkiewicz reaction).142 Iodides are most frequently used as electrophilic coupling partners, though the use of bromides, triflates (30),144 or even some reactive chlorides (31)145 is also possible. Due to the low steric bulk of the acetylenic unit, as well as its exceptional ability in the transduction of electronic effects, the SH reaction is well suited for construction of new (e.g., star-like) molecular architectures through polysubstitution (32).146... 

As mentioned in the introduction, polymer-supported reagents can be used in excess to drive a reaction to completion, without a penalty in terms of purification. However, in many coupling reactions, it is not only an excess of coupling reagent, e.g., a carbodiimide moiety such as 10 (Scheme 2), that is required to drive the reaction to completion, but also an excess of one of the coupling partners. Consequently, new methods have been developed to separate these excess quantities from the product by simple filtration processes (Fig. 3). These techniques are described in more detail in Chapter 1. 

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