Aryltins, reactions

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

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). 

These reactions to form aryl tin bonds could occur by initial oxidative addition of the aryl halide or the distannane. The stoichiometric reaction between [(PPh3)2Pd(Ph)(I)] and Me3SnSnMe3 in the presence of chloride generated good yields of the aryltin product. This result suggests that the reactions occur by initial oxidative addition of aryl halide. 

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)). 

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. 

Phenylacetophenone [AsPhg is superior to PPh3 and P(2-furyl)3 for the reaction between aryltin and organic triflates] [22]. 

Bromo-4-[2-[(l,l-dimethylethoxycarbonyl)amino]phenyl]-5,8-dime-thoxyquinoline [CuBr to accelerate a chemoselective reaction between an aryltin and a heteroaryl triflate] [58]. 

A Diels-Alder reaction between methyl tributylstannylpropiolate and substituted butadienes gives good yields of the 1,4-cyclohexadiene, which can be dehydrogenated to the aryltin reagent [132]. 

Like in the case of an aryltin reagent, an interesting example using Diels-Alder reaction has been reported (Scheme 54) [222]. 

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