Stannanes polymer-bound

Stannane based Hnkers (Tab. 3.8) are used for the StiUe reaction (see below, section 3.3.2.1) onsoHd supports [119]. Nicolaouetal. developed polymer-bound aUcenylstan-nanes to obtain the natural product (S)-zearalenone by an intramolecular StiUe reaction and a cyclative cleavage [120]. 

The copper-catalyzed coupling of polymer-bound aryl iodides with stannanes has also been demonstrated.64... 

Stannaries have become prominent in multifunctional anchoring groups. A polymer-bound tin hydride 41 has been used to hydrostannylate alkynes under the action of palladium-catalysis to give polymer-bound alkenylstannanes 42. These alkenyl stannanes have been employed in intermolecular [45] and intramolecular Stille reactions [46]. Alkenylstannanes can also undergo protonation to give alkenes 44 in a traceless fashion. This linker is therefore multifunctional (Scheme 6.1.12). 

For example, the fluorous stannanes (10) reported by Curran and coworkers (equation 10) are effective substitutes for Bu3SnH in a wide cross-section of free-radical transformations27-30, as are the polymer-bound systems (37) described by Deleuze48,49. 

Functionalized macrocyclic all using polymer-bound stannanes. ... 

Functionalized macrocyclic alkenes can be synthesized by intramolecular Stille coupling using polymer-bound stannanes. The products are released during the coupling process. ... 

Since the renaissance of solid-phase organic chemistry in 1992, carbon-carbon bond formation reactions on solid support have probably been the best studied reactions. Many different facets of the Suzuki, Heck and Stille reactions have been evaluated. The influence of linkers, catalyst, solvents, microwave, polymer-bound aryl halides or polymer-bound arylboronic acids (or stannanes) have been studied in detail. 

Several other types of polymer-bound stannanes have since been reported, including a polymer-bound distannane used in radical-mediated cyclizations and radical addition to acetylenes [87], and stannanes with longer tethers to the polymer [88, 89] applied in the Barton-McCombie deoxygenation of alcohols [90, 91] and... 

Tin hydride reagents are versatile tools for the functionalization of alkenes and alkynes. Based on this concept, Nicolaou and coworkers developed a polymer-bound tin hydride (118) that reacts via Pd-catalyzed hydrostannylation (or nucleophilic attack on the tin chloride with a vinyl lithium) with alkynes to give alkenylstannanes [116]. After further transformation to derivatives 119, the resin-bound substrates undergo proteolytic traceless cleavage to yield unsubstituted alkenes 120. Alternatively, the stannane can be employed for intramolecular Shlle coupling to produce macrolactones 121 in the cleavage step (Scheme 16.28). 

Solid-phase synthesis was initiated by coupling 28 to aminomethylated polystyrene resin 29 in NMP with DIEA as base and DMAP as an acylation catalyst. Stille reactions of the polymer-bound stannane 30 with different aromatic and aliphatic acid chlorides and subsequent cleavage of the Bpoc protecting group by brief treatment with 3% TFA in CHjClj afforded polymer-bound 2-aminoaryl ketones 31 as shown in Scheme 4.1.7. 

C.ii.b. Stille Couplings. A polymer-bound tin hydride has been used to hydrostannylate alkynes under palladium catalysis hydrostaimylation to give polymer-bound alkenyl-stannanes.t Alternatively, the latter could be prepared from a polymer-bound tin chloride and an alkenyllithium or -magnesium halide reagent. These alkenylstannanes were employed in intermolecular as well intramolecular Stille reactions. The inter-molecular reactions provided the coupling products in good yields. In addition, the... 

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