Aryltins reaction with

By reaction with the appropropriate aryl halides can be prepared a variety of aryltin compounds that are not accessible from the reactions involving arylmagnesium halides and organotin halides (88,89) there is evidence that an aryne intermediate may be involved (90). However, for some purposes, such as the addition to carbonyl compounds, ox-iranes, and oxetanes, to give hydroxyalkyltin compounds, the Sn-Mg reagents may have advantages (see Section II,E) (91-93). 

The two most important reactions of aryltin compounds are first, their reaction with electrophiles, when either the tin or the non-tin product may be the aim, or, second, the coupling reactions that they show in the presence of certain transition metals (Equation (51)). 

Table 7-2 Reaction of aryltin compounds with electrophiles Ar-SnX3 —> ArE.

Aryltin reagents have been used similarly to arylaluminum compounds for the preparation of C-glycosides. Particularly applied to reactions with furanose glycals, Daves, etal.,77>78 carried our the reactions shown in Schemes 2.4.2 and 2.4.3. Utilizing palladium acetate to mediate the couplings between glycals and aryltributyltin compounds, p anomeric selectivity was observed in poor to good yields. 

The Stille coupling involves heating a halide, a stannane and a catalyst in a suitable solvent, such as toluene or DMF. No base is required. The conditions are relatively straightforward, with little overall variation, apart from the catalyst. However, if a triflate is used instead of a halide, the reaction may not succeed, as transmetallation of aryltin compounds with arylpalladium triflates is often difficult. Addition of a halide source, such as lithium chloride, usually solves this problem as it allows the formation of the arylpalladium chloride, which can undergo transmetallation. 

These polystannanes presumably arise through the intermediacy of trialkyl/aryltin lithium or Grignard reagents. One way of preparing RjSnLi is to treat tin(II) chloride with three molar equivalents of RLi in ether. Further reaction with SnCl yields (Ph,Sn),SnLi (R = Ph) which may be trapped with PhjSnCl. 

Kang and co-workers have reported reactions of open-chain vinyl-substituted cyclic carbonates with many stabilized and nonstabilized carbon nucleophiles,heteroatom nucleophiles, hydride equivalent,and vinyl and aryltin reagents. Retention of configuration has been observed for malonate, for thiophenolate, and for the conjugate base of phthalimide. In the absence of nucleophile a proton elimination ensues (Scheme 44). The reaction with iodobenzene produces a reductive ring opening by a variant of the Heck reaction. ... 

A -Benzyloxindoles and Af-benzyldihydroisoquinolinones were synthesized via rhodium(I)-catalyzed [2- -2-1-2] cycloaddition of 1,6-diynes with alkynes, palladium(0)-catalyzed arylative cyclization, and palladium(0)-catalyzed coupling reaction with arylboron or aryltin reagents (Scheme 4.37) [41]. When the reactions were conducted under a CO atmosphere, aryl ketones were obtained through... 

With tetiaaiyltin compounds, the reaction can proceed further to the aryltin trihalides ... 

Unactivated aryl iodides undergo the conversion Arl — ArCHj when treated with tris(diethylamino)sulfonium difluorotrimethylsilicate and a palladium catalyst.131 A number of methods, all catalyzed by palladium complexes, have been used to prepare unsymmetrical biaryls (see also 3-16). In these methods, aryl bromides or iodides are coupled with aryl Grignard reagents,152 with arylboronic acids ArB(OH)2,153 with aryltin compounds Ar-SnR3,154 and with arylmercury compounds.155 Unsymmetrical binaphthyls were synthesized by photochemically stimulated reaction of naphthyl iodides with naphthoxide ions in an SrnI reaction.156 Grignard reagents also couple with aryl halides without a palladium catalyst, by the benzyne mechanism.157 OS VI, 916 65, 108 66, 67. 

The palladium-catalyzed reaction of aryl- and vinyl-tin reagents with stereochemically defined allyl chlorides proceeds with overall retention of configuration, indicating that the second step, entailing interaction of the iT-allylpalladium complex and the organotin, proceeds by transmetallation and reductive elimination (attack at Pd, retention) (equations 166 and 167).142145 Comparable results were obtained with cyclic vinyl epoxides and aryltins.143... 

The impurities such as grease, acids, or metals act as catalysts and the driving force of the overall reaction of Eq. (133), once it is initiated, is the formation of a gaseous and solid phase. With careful exclusion of such catalysts, alkyl or aryltin hydrides appear to be stable indefinitely at room temperature. 

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