Reactions of alkynyltins

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

A Vn7Snii9Sn coupliug of 790 Hz has been reported by Wrackmeyer et al for l,F-di(trimethylstannyl)-2-allylboryl-pentadiene-l,4 obtained in the reaction of the corresponding mono-l-alkynyltin with triallylborane, and of 348.0 Hz for l,l-bis(methoxy-ethynyl)(dimethylstannyl)ethene. ... 

The reaction of 1-heptynyltributyltin represents one of the prototypical examples of the Pd-catalyzed cross-coupling reactions of organotins and the first of the Pd-catalyzed alkynylation with alkynyltins. The 1-heptynylboron derivative generated by the treatment of 1-heptynyllithium with (n-Bu)3B is relatively unreactive at room temperature (Entry 10), but it reacts readily under reflux (THE) to give the desired product in 92% yield (Entry 11). This reaction represents the first example of the Pd-catalyzed reaction of... 

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>. 

An example that used this protocol the substrate of which contains a sensitive functionality is depicted in Scheme 45 [202]. 1,3-Diene monoepoxide is easily attacked by a palladium(O) complex to form the corresponding 7r-allylpalladium species. Thus such a process could be banished from the desired selective transformation as depicted in Scheme 46 by the employment of the alkynyltin reagent with an aid of triphenylarsine ligand [203]. Organotin protocol is also convenient for introduction of a small alkynyl moiety such as C2 or C3 or preparation of symmetrical diarylethynes (Scheme 47) [204]. Shirakawa et al. reported recently that iminophosphine 4 is much more effective ligand for palladium than tris(2-furyl)phosphine in this reaction (Scheme 48) [32,205]. 

Alkynyltins. These tins are the most reactive and couple with a variety of electrophiles smoothly, although there is no need to use these reagents if the Sonogashira reaction can substituteJ ... 

I 9 Cross-Coupling Reactions to sp Carbon Atoms Table 9.17 Examples of the Stille alkynyltin cross-couplings with organotriflates. 

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