Intermolecular Stille coupling

Wong reported that stoichiometric amounts of copper(I) chloride alone can promote the intramolecular Stille coupling (equation 138)243. In fact, copper(I)-mediated reaction was cleaner and faster compared with that catalysed by Pd(0) species. Selected examples of intermolecular Stille coupling reactions leading to dienes (Table 25)236a,242b 244, polyenes (Table 26)245 and macrocyclizations (Table 27)246 are given in the respective tables. 

The intermolecular Heck reactions of oxazoles and thiazoles with olefins are not too common. They are rarely high yielding since in several cases they are biased by dehalogenation. Due to this reason the olefination of these systems is usually achieved through Stille coupling with vinylstannanes. 

The furyl- and benzofurylstannanes can be coupled with a variety of electrophiles including aryl [53] and heteroaryl halides [54, 55]. In their synthetic studies towards lophotoxin and pukalide, Paterson and coworkers explored both intermolecular and intramolecular Stille coupling reactions [56]. The intermolecular approach between vinyl iodide 54 and furylstannane 55 was... 

Intermolecular free-radical additions of stannyl radicals to multiple bonds have emerged as important methods for the preparation of tetraorganostannanes which can be reacted further to afford new C—C bonds through transition metal mediated coupling processes (e.g. Stille coupling). There are numerous examples of this chemistry715-737, and this treatise will focus on a few selected examples. 

Another intriguing cascade, of an intramolecular Heck type followed by an intermolecular Stille coupling, produces the dienyne 80 starting from the enyne 78 and the stannane 79 (Scheme 3-24) [175]. The reversed sequence of a Stille-type followed by a... 

Figure 5.4.1 Selected natural products synthesized by Intermolecular alkenyl-alkenyl Stille coupling highlighting the bond formed In the key cross-coupling...

Stille coupling has been used by Li et al to synthesize the donor-acceptor co-polymer P23 consisting of dithienyl-DPP and fused thienothiophene (TT) units. OFET devices fabricated from this polymer showed a high hole mobility of 0.94 cm V s due to significant intermolecular %-% donor-acceptor interactions between TT and DPP fused heterocyclic units.Additionally, a stannyl derivative of dithienothiophene has been recently co-polymerized by Shahid et al. with bis(5-bromo-2-thiophenyl)- and bis(5-bromo-2-selenophe-nyl)-DPP comonomers. Both polymers exhibited ambipolar characteristics in OFET devices. The thiophene-based co-polymer analog showed a higher... 

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... 

A Mitsunobu process simultaneously coupled the enyne acid fragment 4 to /J-lactam 10 and inverted the CIO stereochemistry to the required (S)-configured ester 11 in 93% yield. A deprotection provided alcohol 12, the key /J-lactam-based macrolactonization substrate, which, under conditions similar to those reported by Palomo for intermolecular alcoholysis of /J-lactams (Ojima et al, 1992, 1993 Palomo et al, 1995), provided the desired core macrocycle 13 of PatA 13 (Hesse, 1991 Manhas et al, 1988 Wasserman, 1987). Subsequent Lindlar hydrogenation gave the required E, Z-dienoate. A Stille reaction and final deprotection cleanly provided (-)-PatA that was identical in all respects to the natural product (Romo etal, 1998 Rzasaef al, 1998). This first total synthesis confirmed the relative and absolute configuration of the natural product and paved the way for synthesis of derivatives for probing the mode of action of this natural product. 

Although a fair number of examples of the Ti-promoted intermolecular alkyne-alkene coupling reactions are known, those that display high pair selectivity and regioselectivity are still relatively limited. Some representative examples are shown in Scheme 18 51 53>53a... 

These results suggest that the critical factor in the substrate-mediated intermolecular interactions which occur within the close-packed DHT layer is the inherent strong reactivity of the diphenolic moiety with the Pt surface. The interaction of adsorbates with each other through the mediation of the substrate is of fundamental importance in surface science. The theoretical treatment, however, involves complicated many-body potentials which are presently not well-understood (2.). It is instructive to view the present case of Pt-substrate-mediated DHT-DHT interactions in terms of mixed-valence metal complexes (2A) For example, in the binuclear mixed-valence complex, (NH3)5RU(11)-bpy-Ru(111) (NH 3)5 (where bpy is 4,4 -bipyridine), the two metal centers are still able to interact with each other via the delocalized electrons within the bpy ligand. The interaction between the Ru(II) and Ru(III) ions in this mixed-valence complex is therefore ligand-mediated. The Ru(II)-Ru(III) coupling can be written schematically as ... 

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