352 research outputs found
Gold(I)-Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho-(Alkynyl)styrenes
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)-α-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 ÎČ-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 enantioselectivitiesMinisterio de Economia y Competitividad (MINECO) and FEDER (CTQ2010-15358 and CTQ2013-48937-C2-1-P) and Junta de Castilla y Leon (BU237U13) for financial support. A.M.S. thanks the Junta de Castilla y Leon (Consejeria de Educacion) and the Fondo Social Europeo for a PIRTU contract. M.A.R. and P.G.-G. thank MEC for a "Young Foreign Researchers" (SB2009-0186) contract and MINECO for "Juan de la Cierva" contract, respectivelyThis is the peer reviewed version of the following article: SanjuĂĄn, A. M., Rashid, M. A., GarcĂa-GarcĂa, P., MartĂnez-Cuezva, A., FernĂĄndez-RodrĂguez, M. A., RodrĂguez, F. and Sanz, R. (2015), Gold(I)-Catalyzed Cycloisomerizations and Alkoxycyclizations of ortho-(Alkynyl)styrenes. Chem. Eur. J., 21: 3042â3052. doi: 10.1002/chem.201405789, which has been published in final form at 10.1002/chem.201405789. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archivin
Enantioselective Synthesis of Polycyclic Carbocycles via an AlkynylationâAllylationâCyclization Strategy
ChemInform Abstract: A Mild Negishi Cross-Coupling of 2-Heterocyclic Organozinc Reagents and Aryl Chlorides.
ChemInform Abstract: Direct, Chemoselective N-tert-Prenylation of Indoles by CĂąH Functionalization.
P III /P V =O Catalyzed Cascade Synthesis of NâFunctionalized Azaheterocycles
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An organocatalytic method for the modular synthesis of diverse N-aryl and N-alkyl azaheterocycles (indoles, oxindoles, benzimidazoles, and quinoxalinediones) is reported. The method employs a small-ring organophosphorus-based catalyst (1,2,2,3,4,4-hexamethylphosphetane P-oxide) and a hydrosilane reductant to drive the conversion of ortho-functionalized nitroarenes into azaheterocycles through sequential intermolecular reductive CâN cross coupling with boronic acids, followed by intramolecular cyclization. This method enables the rapid construction of azaheterocycles from readily available building blocks, including a regiospecific approach to N-substituted benzimidazoles and quinoxalinediones
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