- Synthesis of Fused Pyrimido[1,6- a ]indolones via Rhodium(III)-Catalyzed Cascade Annulations
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A novel method for the synthesis of fused pyrimido[1,6- a ]-indolone derivatives by annulation of 2-alkynylaryl aldehydes/2-alkynyl arylidene ketones with N -(pivaloyloxy)-1 H -indole-1-carboxamide catalyzed by rhodium has been accomplished. The reaction proceeds through C-H activation based annulation with alkyne moiety followed by addition of nitrogen on to aldehyde/activated alkene to give the products in moderate to good yields. Highly fluorescent dipyrrinone analogues could be synthesized from the derived products.
- Raji Reddy, Chada,Bodasu, Srinivas,Mallesh, Kathe,Prapurna, Y. Lakshmi
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p. 1127 - 1136
(2020/10/29)
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- Gold-Catalyzed Intermolecular Oxidative Diyne Cyclizations via 1,6-Carbene Transfer
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A vinyl/α-oxo carbene is generated via an α-oxo carbene formation and subsequently transferred across the second alkyne. These highly active species can react with nitriles in an intermolecular fashion to provide substituted oxazoles. This methodology goes through 1,6-carbene shift and offers a range of valuable products. (Figure presented.).
- Wang, Qian,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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p. 755 - 759
(2019/12/11)
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- Synthesis of Benzothiophene-Fused Oxa[6.6.5]tricyclic Skeletons through a Cinchonidine- or NaOH-Promoted Quadruple Domino Sequence
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Two base-promoted quadruple domino reactions between thioaurones and allylic phosphonium salts have been developed to synthesize benzothiophene-fused oxa[6.6.5]tricyclic skeletons in moderate to good yields with excellent stereoselectivity and broad functional-group tolerance. This is a simple and useful protocol for the rapid construction of the umbrella-like oxa[6.6.5]tricyclic skeleton.
- Li, Ke,Wang, Liang,Yu, Aimin,Zhu, Lingli,Zhang, Lei,Gu, Yingchun,Meng, Xiangtai
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supporting information
p. 9665 - 9669
(2019/07/05)
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- Gold-Catalyzed Access to 1H-Isochromenes: Reaction Development and Mechanistic Insight
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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.
- Tomás-Mendivil, Eder,Heinrich, Clément F.,Ortuno, Jean-Claude,Starck, Jér?me,Michelet, Véronique
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p. 380 - 387
(2017/06/07)
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- An Alkyne Diboration/6π-Electrocyclization Strategy for the Synthesis of Pyridine Boronic Acid Derivatives
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A new and efficient synthesis of pyridine-based heteroaromatic boronic acid derivatives is reported through a novel diboration/6π-electrocyclization strategy. This method delivers a range of functionalized heterocycles from readily available starting materials.
- Mora-Radó, Helena,Bialy, Laurent,Czechtizky, Werngard,Méndez, María,Harrity, Joseph P. A.
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supporting information
p. 5834 - 5836
(2016/05/09)
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- Gold(I)-catalyzed cycloisomerizations and alkoxycyclizations of ortho-(alkynyl)styrenes
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Indenes and related polycyclic structures have been efficiently synthesized by gold(I)-catalyzed cycloisomerizations of appropriate ortho-(alkynyl)styrenes. Disubstitution at the terminal position of the olefin was demonstrated to be essential to obtain products originating from a formal 5-endo-dig cyclization. Interestingly, a complete switch in the selectivity of the cyclization of o-(alkynyl)-a-methylstyrenes from 6-endo to 5-endo was observed by adding an alcohol to the reaction media. This allowed the synthesis of interesting indenes bearing an all-carbon quaternary center at C1. Moreover, dihydrobenzo[a]fluorenes can be obtained from substrates bearing a secondary alkyl group at the β-position of the styrene moiety by a tandem cycloisomerization/1,2-hydride migration process. In addition, diverse polycyclic compounds were obtained by an intramolecular gold-catalyzed alkoxycyclization of o-(alkynyl)styrenes bearing a nucleophile in their structure. Finally, the use of a chiral gold complex allowed access to elusive chiral 1H-indenes in good enantioselectivities.
- Sanjun, Ana M.,Rashid, Muhammad A.,Garca-Garca, Patricia,Martnez-Cuezva, Alberto,Fernndez-Rodrguez, Manuel A.,Rodrguez, Flix,Sanz, Roberto
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supporting information
p. 3042 - 3052
(2015/02/05)
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- Platinum-catalyzed cyclization of o-alkynyl(oxo)benzenes with alkenes by 1,2-migration of benzene: Synthesis of 8-oxabicyclo[3.2.1]octane derivatives
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An interesting migration of the rigid structure of benzene was observed when propargylic esters were introduced to the cyclization chemistry of o-alkynyl(oxo)benzene. Various 8-oxabicyclo[3.2.1]octane derivatives with many functional groups could be synthesized from this efficient approach catalyzed by platinum. The high stereo- and regioselectivity involved in this transformation was also attractive. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Shu, Xing-Zhong,Zhao, Shu-Chun,Ji, Ke-Gong,Zheng, Zhao-Jing,Liu, Xue-Yuan,Liang, Yong-Min
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supporting information; experimental part
p. 117 - 122
(2009/07/05)
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- Synthesis of isoquinolines and pyridines by the palladium/copper-catalyzed coupling and cyclization of terminal acetylenes and unsaturated imines: The total synthesis of decumbenine B
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Monosubstituted isoquinolines and pyridines have been prepared in good to excellent yields via coupling of terminal acetylenes with the tert-butylimines of o-iodobenzaldehydes and 3-halo-2-alkenals in the presence of a palladium catalyst and subsequent copper-catalyzed cyclization of the intermediate iminoalkynes. In addition, isoquinoline heterocycles have been prepared in excellent yields via copper-catalyzed cyclization of iminoalkynes. The choice of cyclization conditions is dependent upon the nature of the terminal acetylene that is employed, as only aryl and alkenyl acetylenes cyclize under the palladium-catalyzed reaction conditions that have been developed. However, aryl-, vinylic-, and alkyl-substituted acetylenes undergo palladium-catalyzed coupling and subsequent copper-catalyzed cyclization in excellent yields. The total synthesis of the isoquinoline natural product decumbenine B has been accomplished in seven steps and 20% overall yield by employing this palladium-catalyzed coupling and cyclization methodology.
- Roesch, Kevin R.,Larock, Richard C.
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