Organotin aryltins

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 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... 

In this section we shall discuss papers involving solely or predominantly reactions of aryltins, noting where necessary the other types of organotin mentioned. 

Alkyl and aryltin(IV) diphenyldithioarsenates R Sn(S2AsPh2)4 ( = 2, R = Me, Bu , Ph = 3, R = Me, cy, Ph) are available from the organotin halides and the sodium salt of diphenyldithioarsenates. The dialkyl and trialkyltin species are four-coordinate by spectroscopy whereas the phenyl derivatives are six-coordinate. A structural study of Me2Sn(S2AsMc2)2 reveals a four-coordinate tin center with monodentate coordination of the dithioarsenate." ... 

Pentacoordinate compounds of antimony and bismuth are becoming more prominent as illustrated by the work of Sharutin et al. For example, penta-arylantimony (lOab) and pentaphenylbismuth (16) ary late organotin halides (e.g. RsSnCl (11) and R2SnBr2 3)) to form aryltin derivatives RaSnAr (12), R2SnArX (14) or R2SnAr2 (15), in 78-95% yields. ... 

The tetra-alkyl- and tetra-aryltins are either colourless liquids or white crystalline solids, which are stable to air and water many of them are now available in commercial quantities. In addition to the symmetrical compounds R4Sn where four identical alkyl or aryl groups are attached to tin in a tetrahedral configuration, many unsymmetrical organotins of type... 

Both electron-deficient and electron-rich aryltins are suitable partners for the Stille reaction. The only limitation of the reaction was an ortho substitution on the organotin and the substrate until the recent use of electron-rich and sterically demanding ligands such as P(t-Bu)3, which permitted the synthesis of tetra-ortho-substituted biaryls. A plethora of heterocyclic stannanes [36] were used in Stille couplings. Their major applications concern the synthesis of pharmacologically interesting compounds, as illustrated by the synthesis of an endothelin antagonist [37] (Scheme 6.5), as well the preparation of supramolecular compounds. 

---