Organotin alkynyltins

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]. 

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 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). 

Alkynyltins are considered to be the most reactive organotins and their coupling generally proceeds smoothly [23]. They were used for different types of reactions... 

---