Alkynyltin compounds

Alkynyltin compounds also take part in Stille coupling reactions with alkyl, aryl, or acyl halides or triflates (e.g., Equation (89)).251 These reactions are covered in Volume 11. 

S.6.1. by Reaction of Alkynyltin Compound unit Transition- or Inner Transition-Metal-Carbonyl Complexes. 

The progress of reactions involving tin and lead compounds can readily be monitored by Sn and 207pb NMR. For example, the various products derived from the 1,1-organoboration of 1-alkynyltin compounds can be easily identified by Sn NMR, compounds [23, 24, 25]. 

Multinuclear ( H, 13C, nB) NMR spectroscopy is undoubtly the most useful and powerful method for the investigation of the organoboration of 1-alkynyltin, -germanium, and -silicon compounds allowing not only the structure of the final products to be determined but also the product ratio to be ascertained (Tables 6-8). 

The two acetylenic functions in the silicon or tin derivative make possible a competition between 1 1 and 2 1 reactions (Scheme 39, pathway b), and the product ratio depends significantly on the reaction conditions. For silicon derivatives an excess of 1-boraadamantane in the reaction mixture (acetylenic component added to 1-boraadamantane) leads to the octacyclic compounds 88 (up to 60%), while when the much more reactive 1-alkynyltin analogues are used, a second intramolecular 1,1-organoboration often takes place <2001CEJ775>. The stmcture of 88c (M = Sn, R = Me, R1 = SiMe3) was confirmed by X-ray analysis <2001CEJ775>. 

Alkynyltin and alkynyllead derivatives were extensively studied by PES, together with NMR and pseudopotential calculations88,92,93,97. For the sake of simplicity we will divide the compounds investigated into two classes ... 

The superior ability of alkynyltins to defer Pd-catalyzed alkynylation until after completion of the competing cyclic carbopalladation has been exploited in the synthesis of neocarzinostatin model compounds [85-87] (Scheme 28). 

The condensation used recently for the synthesis of alkynyltins from monosubstituted acetylenes with organotin amines, oxides, and halides 135, 160, 193, 253) has been shown by Davies and Puddephatt to be successful with organolead compounds 45). 

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