Aryltin compounds

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)). 

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. 

Ohe, T. Uemura, S. A novel catalytic activity of Bi(III) salts in Pd(II)-catalyzed atom economical Michael-type hydroarylation of nitroalkenes with aryltin compounds. Tetrahedron Lett. 2002, 43, 1269-1271. 

Various alkyl and aryltin compounds were determined in aquatic matrices, namely sediments, biota and water by means of gas chromatographic methods. In this work, comparisons of single or dual flame photometric detectors and electron capture detectors were reported (Tolosa et al., 1991). Sample preparations included acid digestion, extraction, formation of methyl derivatives and clean-up with alumina prior to gas chromatographic analysis. With the electron capture detector, cold on-column injection of organo-tin chlorides was studied. The conclusion was that a single or dual flame photometric detector equipped with a 600 nm interference filter yielded the best performance for determinations of tin species as methyl derivatives. Detection limits for the method using flame... 

Hexamethylditin is a suitable reagent for Pd-catalyzed metallation of aryl-halides to furnish aryltin compounds that in turn can react in Stille couplings with aryl halides to form biaryl derivatives. Hitchcock and coworkers [ 126] have shown that 2-pyridyl triflate and (hetero)aryl bromides can be coupled to 2-(hetero)aryl pyridines 174 in moderate to good yields (Scheme 66). The underlying principle of this heterocoupling of two aryl (pseudo)hahdes is the selective stannylation of the triflate that is undergoing a faster oxidative addition to the Pd(0) complex than the bromide. 

S.8.5.6.4. by Reaction of Aryltin Compound and Cyciopentadienyltin Compounds with Transition- or Inner Transitlon-Metal-Carbonyl and Other Complexes. 

The aryl-tin bond, like the alkyl-tin bond, is stable to air and moisture, but it is more susceptible to cleavage by electrophiles. Melting points of some aryltin compounds are given in Table 7-1. 

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

Aryltin compounds react with copper(II) nitrate to give, via the intermediate arylcop-per(II) compounds, the corresponding biaryls (equation 7-21).63 Rather better yields have been obtained with Pd(OAc>2 as the catalyst and CuCF which acts as the reoxidant for the catalyst (equation 7-22).67... 

The first group of reactions (13-1-13-3) can be carried out by mixing aliquots of the tin oxide or hydroxide and acid in a solvent such as methanol (e.g. equation 13-7).3 The water can often be conveniently removed by azeotropic dehydration in benzene or toluene, but with aryltin compounds it may be better to use molecular sieves, to avoid the risk of cleaving the aryl-tin bonds.4... 

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. 

Aryltrimethyltins. These aryltin compounds can be obtained from aryl bromides or triflates and (RjSn)2 with a Pd(0) catalyst. 

Biphenyls are also produced when diaryliodonium salts are coupled with aryltin compounds. ... 

Chemical shifts for aryltin compounds are given in Table XV. Attempted correlations of C chemical shifts with Hammett a constants work best with C(l) for the para and meta phenyltin derivatives (203). It must be realized however that such correlations of reactivity parameters (such as o, determining reactivity and chemical shielding are similar. 

In 1998, Oi and Inoue [161] reported early examples of a C-H/C-M coupling to make biaryl compounds. They conducted the coupling of 2-phenylpyridine with an aryltin compound (tetraphenylstaimane) in the presence of a rhodium complex in tetrachloroethane at 120 °C to afford monoarylated compound 120 and diarylated compound 121 in 56% and 20% yield, respectively (Scheme 17.34). 

---