166757-13-7Relevant academic research and scientific papers
Gold-Catalyzed Access to 1H-Isochromenes: Reaction Development and Mechanistic Insight
Tomás-Mendivil, Eder,Heinrich, Clément F.,Ortuno, Jean-Claude,Starck, Jér?me,Michelet, Véronique
, p. 380 - 387 (2017/06/07)
The gold-catalyzed domino cyclization/nucleophilic reaction of ortho-carbonylalkynylaryls has been studied. Thus, 2-(pyridin-2-ylethynyl)benzaldehyde has been chosen to isolate key intermediates that may take part in the reaction mechanism. Employing Hantzsch ester (HEH) as nucleophile, it has been impossible to isolate the corresponding gold-alkenyl specie; however, when methanol was used as solvent (and nucleophile), the expected chelate gold-vinyl complex was isolated and unambiguously characterized by X-ray analysis. When HEH is present in the alcoholic reaction mixture, isotopic studies show that the cleavage of the Au-C bond of gold-vinyl complex proceeds through a protodemetalation pathway, rather than a plausible metal-hydride reductive elimination mechanism. Finally, with the aim of broadening the scope of the cyclization/reduction reaction previously reported, we present that the catalytic system is robust and applicable for a diverse family of challenging substrates presenting ester, aldehyde, ether, alkene, and alkyne functionalities.
An Unusual Example of a 6-Endo-Dig Addition to an Unactivated Carbon-Carbon Triple Bond
Padwa, Albert,Krumpe, Keith E.,Weingarten, M. David
, p. 5595 - 5603 (2007/10/03)
Methyl 2-ethynyl>benzoate was prepared as an intermediate for subsequent conversion to an α-diazo ketone.Under the basic conditions used to hydrolyze the methyl ester, the neighboring hydroxyl functionality underwent reaction with the unactivated acetylenic group, producing a benzopyranyl-substituted α-diazoacetophenone.Treatment of this diazocarbonyl compound with a catalytic quantity of rhodium(II) mandelate afforded a novel dibenzocyclononenone derivative.The reaction proceeds via an initially formed oxonium ylide which rearranges further by means of a 1,2-alkyl shift.A prime factor in determining the direction of internal cyclization to the triple bond is the presence of the carbomethoxy group in the ortho position of the β-phenyl ring.Thus, in contrast with related systems which exhibit a clear preference for 5-exo-dig cyclization at the acetylenic center, the 6-endo-dig addition is the preferred pathway for the o-formyl- and o-carbomethoxy-substituted alkynyl alcohols.Careful monitoring of the reaction actually showed that the reaction proceeds by initial formation of the 5-exo-dig product followed by a novel rearrangement to the 6-endo product.
Intramolecular Addition to an Unactivated Carbon-Carbon Triple Bond via an Apparent 6-Endo Digonal Pathway
Weingarten, M. David,Padwa, Albert
, p. 4717 - 4720 (2007/10/02)
Investigation of an apparent 6-endo-dig cyclization reveals an unusual acid-catalyzed rearrangement of the initially formed benzofuran derivative.
