Ring-closing metathesis for the synthesis of substituted indenols,indenones, indanones and indenes: Tandem RCM-dehydrogenative oxidation and RCM-formal redox isomerization |
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| Institution: | 1. Tarragona, Spain;2. Riverside, CA, USA;1. Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany;2. Department of Nuclear Medicine, University Hospital Aachen, RWTH Aachen University, Pauwelsstr. 30, 52074 Aachen, Germany;1. Moscow Institute of Physics and Technology (State University), Institutskiy per. 9, Dolgoprudny, Moscow Region 141700, Russia;2. Kotel''nikov Institute of Radio-Engineering and Electronics of Russian Academy of Sciences, Mokhovaya Street 11-7, Moscow 125009, Russia;3. Institute on Laser and Information Technologies of Russian Academy of Sciences, Svyatoozerskaya Street 1, Shatura, Moscow Region 140700, Russia;1. Department of Chemistry ‘Ugo Schiff’, University of Firenze, via della Lastruccia 3-13, Sesto Fiorentino, (FI), Italy;2. Associated with Consorzio Interuniversitario Nazionale di ricerca in Metodologie e Processi Innovativi di Sintesi (CINMPIS), Italy;3. Paediatric Neurology Unit and Laboratories, Neuroscience Department, Meyer Children’s Hospital, and Department of Neurosciences, Pharmacology and Child Health. University of Florence, Viale Pieraccini n. 24, 50139 Firenze, Italy;4. Departamento de Química Orgánica, Facultad de Química, Universidad de Sevilla, n/Prof. García González 1, E-41012 Sevilla, Spain;5. Department of Experimental and Clinical Biomedical Sciences, University of Florence, Viale Morgagni 50, 50134 Florence, Italy;1. A. M. Butlerov Institute of Chemistry, Kazan Federal University, 420008 Kazan, Russian Federation;2. A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of the Russian Academy of Sciences, 420088 Kazan, Russian Federation;1. Organisch-Chemisches Institut, Westfälische Wiulhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany;2. Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street Glasgow, UK |
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| Abstract: | A number of substituted indenols have been synthesized using ruthenium-mediated ring-closing metathesis (RCM) with Grubbs second generation catalyst as the key step. The required dienes were synthesized by two strategies. The first entailed the isomerization of 2-allyl-3-isopropoxy-4-methoxybenzaldehyde to its styrene derivative, isopropoxy-4-methoxy-2-propenylbenzaldehyde using RuClH(CO)(PPh3)3]. This compound and 3-isopropoxy-4-methoxy-2-(1-phenyl-propenyl)-benzaldehyde were then treated with vinyl- or isopropenyl-magnesium bromide to afford four of the scaffolds required for the metathesis. As the compound 3-isopropoxy-4-methoxy-2-(1-methyl-2-propenyl)benzaldehyde proved to be difficult to isomerize, the diene substrates 1-3-isopropoxy-4-methoxy-2-(1-methylpropenyl)-phenyl]-prop-2-en-1-ol and 1-3-isopropoxy-4-methoxy-2-(1-methylpropenyl)-phenyl]-2-methylprop-2-en-1-ol were synthesized by the addition of the Grignard reagents to 3-isopropoxy-4-methoxy-2-(1-methyl-2-propenyl)benzaldehyde, followed by isomerization of the arylallyl group to the thermodynamically favoured isomer with potassium t-butoxide. The use of harsher conditions (higher temperature and catalyst loadings) for the metathesis reactions resulted in the formation of substituted indenones, formed by a tandem RCM-dehydrogenative oxidation in the absence of a hydrogen acceptor. Further manipulations of the reaction conditions generated two substituted indanones by way of a tandem RCM-formal redox isomerization sequence. Finally the synthesis of some substituted indenes was accomplished from their corresponding dienes by the use of RCM. |
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