Arylsulfonylacetylenes as Alkynylating Reagents of CH Bonds Activated with Lithium Bases

Abstract

Chamäleon: Eine neue Synthesestrategie für Alkinylderivate nutzt die Reaktion substituierter Arylsulfonylacetylene mit Organolithiumspezies (siehe Schema). Hohe Ausbeuten, eine große Substratbreite und der Verzicht auf Übergangsmetallverbindungen kennzeichnen diese leicht ausführbare CspC sp 2‐Verknüpfungsreaktion.

Strongly Luminous Tetranuclear Gold(I) Complexes Supported by Tetraphosphine Ligands, meso‐ or rac‐Bis[(diphenylphosphinomethyl)phenylphosphino]methane

“…Instead of the expected Michael products, they observed the exclusive formation of the products of alkynylation at the benzylic position44 (see below). Once this behavior had been identified as typical of Truce's reaction and its unexplored large synthetic potential as an alkynylation procedure had been realized, the authors initiated a systematic study to establish the scope and limitations of the method 45,46…”

“…Use of organolithiums in ortho ‐lithiation processes,48 thus avoiding the use of halo derivatives as starting materials, has also been successfully employed in reactions with sulfonylacetylenes (Scheme ) 46. Anisole reacted with n BuLi and different sulfonylated arylacetylenes (regardless of the electronic density on the aryl ring) and TIPS derivatives to form ortho ‐alkynyl‐substituted anisoles in good yields.…”

Palladium‐Catalyzed Oxidative Cross‐Coupling between Heterocycles and Terminal Alkynes with Low Catalyst Loading

“…Initially, the reaction that was carried out in 1,2-dimethoxyethane (DME) at 90 8C for 4 h in the presence of Pd(OAc) 2 (5 mol %) as a catalyst and Ag 2 CO 3 (1.5 equiv) as an oxidant did not give the desired product 3 a, but instead formed a large amount of unwanted alkyne homocoupling by-product 4 ( Table 1, entry 1). Next, we tested the effect of the metal ions of the base, which revealed that Cs 2 CO 3 was the base of choice (entries [5][6]. When simultaneously adding K 2 CO 3 (1 equiv) and PivOH (2 equiv) as additives, we were pleased to find that 3 a was obtained in 35 % yield (entry 4).…”

Palladium‐Catalyzed Oxidative Cross‐Coupling between Heterocycles and Terminal Alkynes with Low Catalyst Loading

“…When simultaneously adding K 2 CO 3 (1 equiv) and PivOH (2 equiv) as additives, we were pleased to find that 3 a was obtained in 35 % yield (entry 4). Next, we tested the effect of the metal ions of the base, which revealed that Cs 2 CO 3 was the base of choice (entries [5][6]. In contrast, the use of acetic acid in place of pivalic acid was ineffective for this reaction (entry 7).…”

“…[2] Recently, the direct alkynylation of (hetero)aromatic compounds has appeared as an alternative to the Sonogashira reaction by using the alkynyl reagents prepared from terminal alkynes, such as alkynyl halides, [3] benziodoxolone-based hypervalent iodine reagents, [4] or arylsulfonylacetylenes. [5] From the viewpoint of step and atom economy, the oxidative cross-coupling [6] between (hetero)arenes and terminal alkynes would be a straightforward and more efficient method for installing alkynyl groups into the (hetero)arene rings, because the need for prefunctionalization of the starting materials would be eliminated. In this context, a few of the seminal examples for such a transformation were recently reported, including the gold-catalyzed alkynylation of electron-rich (hetero)arenes with electron-poor terminal alkynes; [7] the copper-, nickel-, or palladium-catalyzed alkynylation of C-H acidic polyfluoroarenes and azoles; [8] and the palladium-catalyzed alkynylation of C3-blocked 1-methylindoles.…”