Sonogashira synthesis preformed alkynylmetals

A.ii. Sonogashira Alkyne Synthesis versus Pd-Catalyzed Alkynylation with Preformed Alkynylmetals... 

A.ii.d. Comparison of Operational Simplicity. As mentioned earUer, the Sonogashira protocol is operationally somewhat simpler than the use of preformed alkynylmetals. This indeed is the main reason for considering first the Sonogashira protocol in cases where it is very satisfactory. When the starting terminal alkynes are prepared via alkynylmetal intermediates, however, the direct use of alkynylmetals would be more convenient, as demonstrated in a recent synthesis of xerulint (Scheme 4). 

Pd-catalyzed alkyne cross-coupling has become one of the most satisfactory methods for the synthesis of alkynes. As discussed in Sect. HI.2.8, there are two related but discrete protocols, that is, Sonogashira coupling, which does not involve formation of alkynylmetals as preformed and discrete reagents (Sect. HI.2.8.1), and the general... 

---