Sonogashira Alkyne Synthesis

8 Palladium-Catalyzed Alkynylation III.2.8.1 Sonogashira Alkyne Synthesis 

These reactions have been used extensively in the synthesis of eneyne-based acetylenic materials. Reaction conditions vary among workers. The general conditions for coupling between aryl or vinyl halides and terminal acetylenes employ a source of Pd(0), the PPhj ligand, an alkyl amine as a base, Cul cocatalyst, terminal acetylene, and aryl or vinyl halide at temperatures ranging from 25 °C up to 100 °C. 

METAL-CATALYZED CROSS-COUPLING REACTIONS BETWEEN ARYL OR VINYL HALIDES WITH TERMINAL ACETYLENES 

Pd-Catalyzed Cross-Coupling Reactions Between Aryl or Vinyl Halides with Terminal Acetylenes 

As mentioned earlier, both Dieck and Heck and Cassai developed this procedure as an extension into acetylenes of the Heck Pd-catalyzed arylation of alkenes. As it requires 

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K. Sonogashira, Sonogashira Alkyne Synthesis, in Handbook of Organopalladium Chemistry for Organic Synthesis , ed. E. Negishi, John Wiley Sons, Hohoken, NJ, 2002, p. 493. 

As discussed in Sect, ni.2.8.1, the Sonogashira alkyne synthesis f and related Heck-type alkynylation using terminal alkynes as reagents collectively offer widely applicable and generally satisfactory procedures for Pd-catalyzed alkynylation. Even so, various limitations and difficulties associated with the Sonogashira and related reactions have... 

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

A.ii.c. Other Limitations and Difficulties Associated with the Sonogashira Alkyne Synthesis. Other limitations and difficulties observed with the Sonogashira alkyne synthesis include (i) alkyne dimerization, which appears to be induced by radicals, and (ii) addition of amines to alkynes as exemplified in Scheme... 

A.ii.b. Electronic and Steric Impedance in the Sonogashira Alkyne Synthesis. There have... 

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