Aryl halides, triflates

B.ii. Structure of Arylpalladium(II) Complexes Formed in Oxidative Addition to Aryl Halides/Triflates as a Function of the Precursors of the Palladium(O) and the Ligand... 

B.xiv.c. Intermolecular Heck Reactions on Polymeric Support. Combinatorial chemistry has initiated a reappraisal and consequent renaissance in synthesis of compounds attached to polymeric supports. Therefore, it comes as no surprise that Pd-catalyzed reactions are among the most widely explored reactions for the generation of combinatorial libraries on solid phase. The first example of the intermolecular Heck reaction on solid phase was reported in 1994. In this article, 4-vinylbenzoic acid was attached to Wang resin and coupled with aryl halides/triflates under catalysis with Pd(OAc)2 (Scheme 45). Similar... 

Reactions of Phosphines Palladium-catalyzed coupling of triarylphosphine can be accomplished with aryl bromides and triflates [222] (Scheme 20.66). A solvent-free approach has been demonstrated with improved yield [223]. The use of excess of triarylphosphine is crucial for second oxidative addition. The substrate scope can be extended to aryl chlorides employing Pd/C in the presence of Nal [224]. Scheme 20.66 shows the catalytic cycle. The oxidative addition of Pd(0) I with aryl halides/triflates can give the intermediate Pd(II) II that can lead to the formation... 

SCHEME 20.66 Hiosphination of aryl halides/triflates using triarylphosphines. 

Transition metal catalyzed coupling between aryl halides/triflates and diboronyl reagents... 

Reaction with Alkyl Halides. The Grignard reagent (1) can be alkylated by allyl halides to afford the homoallylsilane. The use of a nickel(II) catalyst facilitates coupling of the Grignard reagent (1) to vinyl halides and aryl halides, triflates and O-carbamates and provides a useful method for the preparation of allyl- andbenzylsilanes (eq 7). Palladium catalysis is also effective to couple (1) with vinyl halides. 

Enynes and arenynes are available from the Pd(Ph3P)4-catalyzed coupling of metalated alkynes (Mg, Al, 4,27 2n, 7f,28 Sn 29) with vinyl or aryl halides, triflates or phosphates (eq 8). Alternatively, 1-haloalkynes and metalated alkenes (B 4 orZn i7 ) can be utilized in similar procedures. 

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