Categories: C-C Bond Formation > Arenes, Alkynes >
Alkynylation
Name Reactions
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Versatile Cross Coupling Methods: Hiyama Coupling (R-X + R'-SiR''3) Hiyama-Denmark Coupling (R-X + R-SiMe2OH) Kumada Coupling (R-X + R'-MgX) Negishi Coupling (R-X + R'-ZnX) Stille Coupling (R-X + R'-SnR''3) Suzuki Coupling (R-X + R'-BY3) |
Recent Literature
An efficient ligand-, copper-, and amine-free palladium-catalyzed
Sonogashira reaction of aryl iodides and bromides with terminal alkynes at
room temperature has been developed. The key reagent is tetrabutylammonium
acetate as the base. This method tolerates a broad range of functional
groups.
S. Urgaonkar, J. G. Verkade, J. Org. Chem., 2004,
69, 5752-5755.
General protocols for the
palladium-catalyzed coupling of aryl chlorides and alkynes and aryl
tosylates and alkynes were developed. Addition of a copper cocatalyst can
inhibit product formation. In the case of highly active catalysts, screening for
new catalyst systems need to be carried out both in the presence and absence of
copper.
D. Gelman, S. L. Buchwald, Angew. Chem. Int. Ed., 2003, 42,
5993-5996.
The palladium-catalyzed cross-coupling reaction of potassium
alkynyltrifluoroborates with aryl halides or triflates proceeds readily with
moderate to excellent yields. The potassium alkynyltrifluoroborates are air- and
moisture-stable crystalline solids that can be stored indefinitely, which will
provide an advantage in applications to combinatorial chemistry.
G. A. Molander, B. W. Katona, F. Machrouhi, J. Org. Chem., 2002,
67, 8416-8423.
A triethylamine-catalyzed metalation of terminal
alkynes with trimethylaluminum (a readily available, inexpensive, and nontoxic
metalating agent) gives alkynyldimethylaluminum reagents. These compounds react
efficiently with various aromatic and heterocyclic halides in the presence of a
palladium catalyst offering a simple entry to numerous internal alkynes.
B. Wang, M. Bonin, L. Micouin, Org. Lett., 2004, 6,
3481-3484.
Cross-Coupling of Alkynylsilanols with Aryl Halides Promoted by Potassium
Trimethylsilanolate
S. E. Denmark, S. A. Tymonko, J. Org. Chem., 2003,
68, 9151-9154.
Various substituted phenols are ethynylated at the ortho position with
silylated chloroethyne in the presence of a catalytic amount of GaCl3
and lithium phenoxide. The lithium salt is essential for the catalysis, and
addition of 2,6-di(tert-butyl)-4-methylpyridine inhibits desilylation
and hydration of the products. The mechanism is discussed.
K. Kobayahi, M. Arisawa, M. Yamaguchi, J. Am. Chem. Soc., 2002,
124, 8528-8529.
