Synthesis Of Internal Alkynes Research Articles

Synthesis of Internal Alkynes through an Effective Tandem ­Elimination–Hydrodebromination–Cross-Coupling of gem-­Dibromoalkenes with Halobenzenes

Carbon–carbon couplings are among the most important strategies for constructing functional molecules in organic synthetic chemistry, and cheap, diverse, and readily available coupling partners are crucial to these diverse reactions. In this contribution, we report the first palladium-catalyzed C–C cross-coupling reaction of two kinds of organic halide, a gem-dibromoalkene and a halobenzene, as the starting materials. Terminal alkynes were generated in situ through a tandem elimination–hydrodebromination process, and the internal alkyne final products were synthesized in one pot. The reaction proceeded under simple, facile, and classic copper-free Sonogashira coupling reaction conditions in good to excellent yields.

ChemInform Abstract: Synthesis of Internal Alkynes by Pd(PPh3)4/TMEDA‐Catalyzed Kumada Cross‐Coupling of Alkynyl Halides with Grignard Reagents.

Alkynes serve as prevalent intermediates in the synthesis of natural products and pharmaceuticals. We here described a new and efficient route to internal alkynes by Pd-catalyzed Kumada cross-coupling reactions of alkynyl halides with Grignard reagents. In the presence of Pd(PPh3)4 and N1,N1,N2,N2-tetramethylethane-1,2-diamine (TMEDA), a variety of alkynyl halides underwent Kumada coupling with Grignard reagents, giving the corresponding internal alkynes in moderate to good yields.

Synthesis of Internal Alkynes by Pd(PPh3)4/TMEDA‐Catalyzed Kumada Cross‐Coupling of Alkynyl Halides with Grignard Reagents

AbstractAlkynes serve as prevalent intermediates in the synthesis of natural products and pharmaceuticals. We here described a new and efficient route to internal alkynes by Pd‐catalyzed Kumada cross‐coupling reactions of alkynyl halides with Grignard reagents. In the presence of Pd(PPh3)4 and N1,N1,N2,N2‐tetramethylethane‐1,2‐diamine (TMEDA), a variety of alkynyl halides underwent Kumada coupling with Grignard reagents, giving the corresponding internal alkynes in moderate to good yields.

ChemInform Abstract: Synthesis of Internal Alkynes Through the Pd‐Catalyzed Coupling of Heteroaryl Halides with Terminal Alkynes.

Abstract3‐Bromo‐indole and 2‐bromo‐benzimidazole don′t give any traceable coupling products due to the occurrence of multiple side reactions as indicated by TLC.

Synthesis of Internal Alkynes through the Pd‐Catalyzed Coupling of Heteroaryl Halides with Terminal Alkynes

AbstractSonogashira‐type cross‐couplings of functionalized heterocyclic halides with terminal alkynes were performed efficiently at room temperature. The heteroaryl halides were easily prepared from the corresponding heterocyclic compounds. The catalytic system tolerated a very broad scope of substrates; oxazoles, thiazoles, and furans participate in this type of reaction for the first time. This reaction provides an efficient method for the direct functionalization of heterocycles.

Highly Efficient Copper‐Catalyzed Synthesis of Internal Alkynes via Aerobic Oxidative Arylation of Terminal Alkynes

AbstractWe have developed a novel and highly efficient, copper‐catalyzed synthesis of internal alkynes via oxidative couplings of aromatic boronic acids with terminal alkynes at room temperature. The protocol uses inexpensive copper(I) oxide [Cu2O] as the catalyst, oxygen in the air as the stoichiometric oxidant; no ligand and sealed reaction vessels are required, and remarkable functional group tolerability is observed with coupling occurring.

Synthesis of internal alkynes via one-pot palladium-catalyzed and dehydrobromination reactions of 1,1-dibromo-1-alkenes

Tandem palladium-catalyzed cross-coupling of alkyl, alkenyl, alkynyl, aryl, and heteroaryl 2-substituted 1,1-dibromo-1-alkenes with aryl or heteroaryl boronic acids or borate esters and dehydrobromination of the intermediate coupled products afforded internal alkynes in moderate to good yields (up to 89%). The synthesis has been carried out in a one-pot process and in a two-step sequence according to the nature of the starting 1,1-dibromoalkenes. The reported protocol is compatible with the presence in the 1,1-dibromo-1-alkene molecule of additional reactive halogen–carbon bonds, thus allowing to build up more complex alkyne derivatives.