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Updated: Sep 18, 2025
Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Recent advances in transition metal-catalyzed alkyne annulations: applications in organic synthesis
Kommu Nagesh1, N Sivasenkar Reddy1, Shaik Kareem1
1Fluoro-Agrochemicals, CSIR-Indian Institute of Chemical Technology, Hyderabad, India-500 007. basireddy@iict.res.in.
Abstract:
Transition metal-catalyzed alkyne annulation has emerged as a powerful strategy for constructing diverse cyclic frameworks with high efficiency and selectivity. This methodology exploits the unique reactivity of transition metals to activate alkynes, enabling the formation of carbocycles and heterocycles. Recent advances-including cooperative catalysis, dual-catalyst systems, and electrochemical transformations-have significantly broadened the scope of achievable structures. The development of novel catalysts and optimized conditions has facilitated the synthesis of complex architectures relevant to pharmaceuticals, natural products, and materials science. Mechanistic studies have enhanced the understanding of reaction pathways, improving control over regio- and stereoselectivity. Incorporating green chemistry principles has further increased the sustainability of these protocols. This review highlights key mechanistic insights, synthetic applications, and future directions in the evolving field of transition metal-catalyzed alkyne annulations.
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02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
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02:34Preparation of Alkynes: Dehydrohalogenation
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
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02:42Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
02:38Electrophilic Addition to Alkynes: Halogenation
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