Arylstannanes coupling

Aryl halides react with a wide variety of aryl-, alkenyl- and alkylstan-nanes[548-550]. Coupling of an aryl tritlate with an arylstannane is a good preparative method for diaryls such as 688. The coupling of alkenylstannanes with alkenyl halides proceeds stereospecifically to give conjugated dienes 689. The allylstannane 690 is used for allylation[397,546,551-553]. Aryl and enol triflates react with organostannanes smoothly in the presence of LiCl[554]. 

The intramolecular coupling of organostannanes is applied to macrolide synthesis. In the zearalenone synthesis, no cyclization was observed between arylstannane and alkenyl iodide. However, intramolecular coupling take.s place between the alkenylstannane and aryl iodide in 706. A similar cyclization is possible by the reaction of the alkenylstannane 707 with enol triflate[579]. The coupling was applied to the preparation of the bicyclic 1,3-diene system 708[580]. 

For coupling, the cheaper aryl fluorosulfonate 713 is used as an alternative to the expensive aryl triflates to give the same results[473]. The arenesulfonates 714 are active for the reaction with vinylstannanes when dppp and LiCI are used in DMSO[583], The bromide 715 attacks the arylstannane moiety selectively without reacting with the organoboron moiety in 716 in the absence of a base[584]. 

The allylstannane 474 is prepared by the reaction of allylic acetates or phosphates with tributyltin chloride and Sml2[286,308] or electroreduction[309]. Bu-iSnAlEt2 prepared in situ is used for the preparation of the allylstannane 475. These reactions correspond to inversion of an allyl cation to an allyl anion[3l0. 311], The reaction has been applied to the reductive cyclization of the alkenyl bromide in 476 with the allylic acetate to yield 477[312]. Intramolecular coupling of the allylic acetate in 478 with aryl bromide proceeds using BuiSnAlEti (479) by in situ formation of the allylstannane 480 and its reaction with the aryl bromide via transmetallation. (Another mechanistic possibility is the formation of an arylstannane and its coupling with allylic... 

Porco s pathway to complete the synthesis of (- )-kinamycin C (3) is shown in Scheme 3.8. The arylstannane 34 and the a-bromoenone 35 were efficiently coupled by a Stille reaction using tris(dibenzylideneacetone)dipalladium and triphenylarsine... 

Innumerable aryl- and heteroarylstannanes take part in Stille couplings with halopyridines. In one such example, the union of arylstannane 106 and 4-bromopyridine furnished arylpyridine 107 [90], Arylstannane 106 was prepared from the Pd-catalyzed reaction of hexabutylditin with iodoarene 105, which arose from aminobenzolactam 104 via a Sandmeyer reaction. 

Disubstituted 4-chloro-2-cyclobutenones 75 undergo the palladium-catalyzed cross-coupling reaction with vinyl- and arylstannanes 76 or vinylzir-conium reagents to give the 4-R sa,-2-cyclobutenones 77. Without isolation, these cyclobutenones 77 are rearranged to the substituted phenols 78 on thermolysis [38], Application of this method to the stannylated heteroaromatics 79 provides a synthetic route to the aromatic benzoheterocycles 80 [39]. (Scheme 27 and 28)... 

Stille cross-coupling and reductive N-heteroannulation steps. lodination of 1033, followed by Stille cross-coupling of the corresponding iodo derivative 1034 with the arylstannane 1035, gave the annotation precursor 1036. Reductive N-heteroannula-tion of 1036 afforded the carbazolone 1001, which was previously (99) (see Scheme 5.143) used to prepare clausenalene (90) via a Wolff-Kishner reduction followed by aromatization (659) (Scheme 5.155). 

Carbonylative cross-coupling reaction between triarylbismuth(V) compounds and organostannanes is smoothly catalyzed by PdCl2 under 1 atm CO at room temperature (Scheme 48) [34]. Not only arylstannanes, but also heteroaryl-, alkynyl-, and vinyltributylstannanes were employed efficiently. 

Methylthio- and phenylthiopyrazines 121 undergo cross-coupling with arylstannanes in the presence of palladium catalyst and copper(l) 3-aminosalicylate to afford 92-93% yields of arylpyrazines 122 (Equation 23) <20030L801>. 

The Stille coupling of 2-chloro-5-tributylstannylpyridine with an enantiopure 2-iodo-cyclohexenon (7.29.) derivative formed the basis of the total synthesis of (+)-epibatidine. The reaction is a nice example of the chemical inertness of arylstannanes and the mildness of the coupling conditions. Both the enone moiety and the chiral ally lie centre remained untouched in the process. The effective coupling required the use of a soft ligand, triphenylarsine and the addition of copper(I) iodide as co-catalyst.40... 

An early attempt to use the Stille reaction on solid support is detailed in a paper from 1994 by Deshpande.57 In this, an aryl iodide linked to Rink amide or Wang resin is coupled to a number of vinyl and one arylstannanes (Scheme 23). The protocol used only 5 mol % Pt dba and proceeded in typically 90% yield at 45°C. Interestingly, the reactions were simply left to stand (rather than being shaken) overnight. 

Coupling of an aryl triflate with an arylstannane is a good mediod for the preparation of biaryls and other bis-aromatic species of all types. Coupling of vinyl groups takes place with retention of stereochemistry. Furdiermore transfer of die allyl group occurs smoothly. 

Optimum conditions for the coupling of the alkenyl triflates 330 with the arylstannanes 331 have been studied. Ligandless Pd complexes such as Pd(dba)2 are most active in the reaction of the enol triflate. PI13P inhibits the reaction. NMP as a polar solvent gives the best results. The use of tri(2-furyl)phosphine and Ph As in the coupling of stannanes with the halides and triflates increases the rate of the transmetallation of the stannanes to Pd, which is thought to be the rate-... 

The scope and limitations of Pd(0)-mediated coupling reactions between aromatic halides linked to a polystyrene resin and boronic acid derivatives (Suzuki coupling) or arylstannanes (Stille coupling) have been reported. For all the reactions, the conditions were optimized and evaluated with various reagents. In most cases, products were obtained in excellent yields upon cleavage from the solid support (Eq. (63)) [101]. 

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