76928-53-5Relevant academic research and scientific papers
Diastereoselective, Zinc-Catalyzed Alkynylation of α-Bromo Oxocarbenium Ions
Haidzinskaya, Tatsiana,Kerchner, Hilary A.,Liu, Jixin,Watson, Mary P.
supporting information, p. 3857 - 3859 (2015/08/18)
We have developed a bromination/alkynylation sequence that enables efficient transformation of simple cyclic enol ethers to difunctionalized products. The success of this strategy relies on a highly diastereselective, zinc-catalyzed addition of terminal a
Ruthenium-catalyzed propargylic substitution reactions of propargylic alcohols with oxygen-, nitrogen-, and phosphorus-centered nucleophiles
Nishibayashi, Yoshiaki,Milton, Marilyn Daisy,Inada, Youichi,Yoshikawa, Masato,Wakiji, Issei,Hidai, Masanobu,Uemura, Sakae
, p. 1433 - 1451 (2007/10/03)
The scope and limitations of the ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with heteroatom-centered nucleophiles are presented. Oxygen-, nitrogen-, and phosphorus-centered nucleophiles such as alcohols, amines, amides, and phosphine oxide are available for this catalytic reaction. Only the thiolate-bridged diruthenium complexes can work as catalysts for this reaction. Results of some stoichiometric and catalytic reactions indicate that the catalytic propargylic substitution reaction proceeds via an allenylidene complex formed in situ, whereby the attack of nucleophiles to the allenylidene Cγ atom is a key step. Investigation of the relative rate constants for the reaction of propargylic alcohols with several para-substituted anilines reveals that the attack of anilines on the allenylidene Cγ atom is not involved in the rate-determining step and rather the acidity of conjugated anilines of an alkynyl complex, which is formed after the attack of aniline on the C γ atom, is considered to be the most important factor to determine the rate of this catalytic reaction. The key point to promote this catalytic reaction by using the thiolate-bridged diruthenium complexes is considered to be the ease of the ligand exchange step between a vinylidene ligand on the diruthenium complexes and another propargylic alcohol in the catalytic cycle. The reason why only the thiolate-bridged diruthenium complexes promote the ligand exchange step more easily with respect to other monoruthenium complexes in this catalytic reaction should be that one Ru moiety, which is not involved in the allenylidene formation, works as an electron pool or a mobile ligand to another Ru site. The catalytic procedure presented here provides a versatile, direct, and one-step method for propargylic substitution of propargylic alcohols in contrast to the so far well-known stoichiometric and stepwise Nicholas reaction.
A new procedure for highly stereoselective and regioselective synthesis of 2-ethynyl-3-hydroxytetrahydropyran derivatives based on alkyne-Co2(CO)6 complex
Mukai, Chisato,Sugimoto, Yu-Ichi,Ikeda, Yoshitaka,Hanaoka, Miyoji
, p. 823 - 850 (2007/10/03)
Treatment of trans-epoxides 3 with Co2(CO)8 gave the corresponding cobalt complexes, which were subsequently exposed to a catalytic amount of BF3·OEt2 at -78°C to provide exclusively cis-2-ethynyl-3- hydroxytetrahydropyran derivatives via endo mode cyclization pathway. cis- Congeners, cis-3 afforded the corresponding trans tetrahydropyran derivatives exclusively. This novel cyclization has been found to proceed with retention of configuration at the propynyl stereogenic center. Requirement for stereoselectivity in cyclization was discussed.
Acetylenes as Potential Antarafacial Components in Concerted Reactions. Formation of Pyrroles from Thermolyses of Propargylamines, of a Dihydrofuran from a Propargylic Ether, and of an Ethylidenepyrrolidine from a β-Amino Acetylene
Viola, Alfred,Collins, John J.,Filipp, Nicholas,Locke, John S.
, p. 5067 - 5075 (2007/10/02)
A thermal cyclization of acetylenic compounds provides evidence for the ability of acetylenic links to act as antarafacial components in processes.The cyclization competes with the normally favored acetylenic retro-ene reaction.Propargylic amines, without substituents whose presence would hinder a tight cyclic transition state, yield intermediate pyrrolines whose subsequent hydrogen elimination affords pyrroles in small amounts.The same process in 2-ethynyltetrahydropyran affords 8-oxabicyclooctane in 35percent yield.A related thermal reaction of N-methyl-3-hexyn-1-amine provides a quantitative transformation to N-methyl-2-ethylidenepyrrolidine in a nominal s + 2a + 2s + 2s> Moebius process, wherein the acetylenic unit is the antarafacial component.Evidence for concertedness in these reactions is discussed.
