Recent Extensions to the Sonogashira Cross-Coupling Protocol

6 Recent Extensions to the Sonogashira Cross-Coupling Protocol 

2 Substrate Scope and Leaving Croup Developments From its early days in the 1970s, the scope of the Sonogashira reaction has successively been widened far beyond the use of simple iodo-, bromo-, and chloroarenes or vinyl haUdes. Neutral and charged heteroarenes, such as chlorotetrazines [135], bromoquinohzium 

The competition between the undesired hydride eHmination and C(sp )-C(sp) coupling is further negatively affected by the substoichiometric amounts of the in sitM-generated Cu-alkynyl species 10 required for the transmetallation step. Fu et al. 

Along with the aforementioned developments, several less common electrophiles, such as aryldiazonium salts [140], arenesulfonyl chlorides [141], triflates and tosylates [142], or tetraphenylphosphonium chloride [143], have successfully been appHed in the Sonogashira reaction in place of aryl halides. 

3 Electrophilic Alkynylation The term inverse Som ashira coupling was introduced by Trofimov et al. [144] in 2004, who observed cross-coupling of l-acyl-2-bromoacetylenes with pyrroles on the AljOj surface at rt under solvent-free 

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