808737-51-1Relevant articles and documents
Atom-Economical Cross-Coupling of Internal and Terminal Alkynes to Access 1,3-Enynes
Liu, Mingyu,Tang, Tianhua,Apolinar, Omar,Matsuura, Rei,Busacca, Carl A.,Qu, Bo,Fandrick, Daniel R.,Zatolochnaya, Olga V.,Senanayake, Chris H.,Song, Jinhua J.,Engle, Keary M.
, p. 3881 - 3888 (2021/04/06)
Selective carbon-carbon (C-C) bond formation in chemical synthesis generally requires prefunctionalized building blocks. However, the requisite prefunctionalization steps undermine the overall efficiency of synthetic sequences that rely on such reactions, which is particularly problematic in large-scale applications, such as in the commercial production of pharmaceuticals. Herein, we describe a selective and catalytic method for synthesizing 1,3-enynes without prefunctionalized building blocks. In this transformation several classes of unactivated internal acceptor alkynes can be coupled with terminal donor alkynes to deliver 1,3-enynes in a highly regio- and stereoselective manner. The scope of compatible acceptor alkynes includes propargyl alcohols, (homo)propargyl amine derivatives, and (homo)propargyl carboxamides. This method is facilitated by a tailored P,N-ligand that enables regioselective addition and suppresses secondary E/Z-isomerization of the product. The reaction is scalable and can operate effectively with as low as 0.5 mol % catalyst loading. The products are versatile intermediates that can participate in various downstream transformations. We also present preliminary mechanistic experiments that are consistent with a redox-neutral Pd(II) catalytic cycle.
Gold-catalyzed cyclization of nonterminal propargylic amides to substituted alkylideneoxazolines and-oxazines
Hashmi, A. Stephen K.,Schuster, Andreas M.,Schmuck, Martin,Rominger, Frank
supporting information; experimental part, p. 4595 - 4602 (2011/10/03)
The substrate scope of the gold-catalyzed cyclization of nonterminal propargylic amides to oxazolines and oxazines was investigated. Sixteen alkyl-substituted and 35 aryl-substited substrates were prepared by a very variable route from trimethylsilyl-(TMS
Gold catalysis: Mild conditions for the synthesis of oxazoles from N-propargylcarboxamides and mechanistic aspects
Hashmi, A. Stephen K.,Weyrauch, Jan P.,Frey, Wolfgang,Bats, Jan W.
, p. 4391 - 4394 (2007/10/03)
(Chemical Equation Presented) 2,5-Disubstituted oxazoles are synthesized from the corresponding propargylcarboxamides under mild reaction conditions via homogeneous catalysis by AuCl3. While monitoring the conversion via 1H NMR spectroscopy, an intermediate 5-methylene-4,5-dihydrooxazole can be observed and accumulated up to 95%, being the first direct and catalytic preparative access to such alkylidene oxazolines. The intermediate was fully characterized and can be trapped at -25°C for several weeks. Deuteration experiments show a stereospecific mode of the two first steps of the reaction.
