- Dehydrative Coupling of Benzylic Alcohols Catalyzed by Br?nsted Acid/Lewis Base
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Traditional cross-coupling reactions show some disadvantages like the use of organohalides or the production of stoichiometric amounts of waste. The dehydrative homo- or heterocoupling of alcohols therefore arises as an interesting approach for a highly atom-economical formation of carbon–carbon bonds, since water is produced as the only by-product. We herein report a simple and direct, metal-free protocol for the synthesis of olefins by applying catalytic amounts of a sulfonic acid and triphenylphosphane under air. A variety of olefins could be synthesized from benzylic alcohols under relatively mild conditions. Additionally, dehydrative hydroarylation of benzylic alcohols with electron-rich arenes was possible by using only Br?nsted acid under otherwise same reaction conditions. We could show that phosphane additives are essential to overcome oligomerization as main side reaction by the occupancy of the reactive carbocation intermediate.
- B?ldl, Marlene,Fleischer, Ivana
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- Annulative π-Extension of Unactivated Benzene Derivatives through Nondirected C-H Arylation
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Annulative π-extension chemistry provides a concise synthetic route to polycyclic arenes. Herein, we disclose a nondirected annulation approach of unactivated simple arenes. The palladium-catalyzed 2-fold C-H arylation event facilitates tandem C-C linkage relays to furnish fully benzenoid triphenylene frameworks using cyclic diaryliodonium salts. The inseparable regioisomeric mixture of 1- and 2-methyltriphenylenes is identified by the combined analysis of ion mobility-mass spectrometry, gas-phase infrared spectroscopy, and molecular simulation studies.
- Lee, Jae Bin,Jeon, Min Ho,Seo, Jeong Kon,Von Helden, Gert,Rohde, Jan-Uwe,Zhao, Bum Suk,Seo, Jongcheol,Hong, Sung You
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supporting information
p. 7004 - 7008
(2019/09/07)
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- SN1 reactions in supercritical carbon dioxide in the presence of alcohols: The role of preferential solvation
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Ethanol (3b) inhibits SN1 reactions of alkyl halides 1 in supercritical carbon dioxide (scCO2) and gives no ethers as products. The unexpected behaviour of alcohols 3 in the reaction of alkyl halides 1 with 1,3-dimethoxybenzene (2) in scCO2 under different conditions is rationalised in terms of Br?nsted and Lewis acid-base equilibria of reagents, intermediates, additives and products in a singular solvent characterised by: (i) the strong quadrupole and Lewis acid character of carbon dioxide, which hinders SN2 paths by strongly solvating basic solutes; (ii) the weak Lewis base character of carbon dioxide, which prevents it from behaving as a proton sink; (iii) the compressible nature of scCO2, which enhances the impact of preferential solvation on carbon dioxide availability for the solvent-demanding rate determining step.
- Delgado-Abad, Thais,Martínez-Ferrer, Jaime,Acerete, Rafael,Asensio, Gregorio,Mello, Rossella,González-Nú?ez, María Elena
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supporting information
p. 6554 - 6560
(2016/07/15)
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- From the gold-catalysed benzylation of arenes to the regio- and stereoselective synthesis of procyanidins dimers
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This work reports on a new intermolecular C-C coupling reaction between electron rich arenes and benzylic alcohols or ethers, catalysed by gold(III) salts, or other catalysts such as gold(I) and iron (III), and its application to the regio- and stereoselective synthesis of procyanidins dimers B1 and B3.
- Fabre, Sandy,Gueroux, Marie,Nunes, Emeline,Szlosek-Pinaud, Magali,Pianet, Isabelle,Fouquet, Eric
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p. 3045 - 3051
(2015/05/04)
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- Graphene-Catalyzed Direct Friedel-Crafts Alkylation Reactions: Mechanism, Selectivity, and Synthetic Utility
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Transition-metal-catalyzed alkylation reactions of arenes have become a central transformation in organic synthesis. Herein, we report the first general strategy for alkylation of arenes with styrenes and alcohols catalyzed by carbon-based materials, exploiting the unique property of graphenes to produce valuable diarylalkane products in high yields and excellent regioselectivity. The protocol is characterized by a wide substrate scope and excellent functional group tolerance. Notably, this process constitutes the first general application of graphenes to promote direct C-C bond formation utilizing polar functional groups anchored on the GO surface, thus opening the door for an array of functional group alkylations using benign and readily available graphene materials. Mechanistic studies suggest that the reaction proceeds via a tandem catalysis mechanism in which both of the coupling partners are activated by interaction with the GO surface.
- Hu, Feng,Patel, Mehulkumar,Luo, Feixiang,Flach, Carol,Mendelsohn, Richard,Garfunkel, Eric,He, Huixin,Szostak, Michal
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supporting information
p. 14473 - 14480
(2015/11/27)
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- Supercritical carbon dioxide: A promoter of carbon-halogen bond heterolysis
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Amazing reaction medium: Supercritical carbon dioxide, with zero dipole moment, lower dielectric constant than pentane, and non-hydrogen-bonding behavior, ionizes carbon-halogen bonds, dissociates the resulting ion pairs, and escapes from capture by the carbocation intermediates at temperatures above 40 °C. These properties allow the observation of carbocation chemistry in the absence of acids.
- Delgado-Abad, Thais,Martinez-Ferrer, Jaime,Caballero, Ana,Olmos, Andrea,Mello, Rossella,Gonzalez-Nunez, Maria Elena,Perez, Pedro J.,Asensio, Gregorio
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supporting information
p. 13298 - 13301
(2014/01/06)
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- Cationic Iron(III) porphyrin catalyzed dehydrative friedel-crafts reaction of alcohols with arenes
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Alcohols react with arenes in the presence of cationic iron(III) porphyrin catalyst. The reaction involves the formation of the C-C bond via dehydration, which is formal Lewis acid catalyzed Friedel-Crafts reaction. Georg Thieme Verlag Stuttgart, New York.
- Teranishi, Satoru,Kurahashi, Takuya,Matsubara, Seijiro
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supporting information
p. 2148 - 2152
(2013/10/21)
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- Microwave-accelerated alkylation of arenes/heteroarenes with benzylic alcohols using antimony(III) chloride as catalyst: Synthesis of O-heterocycles
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An efficient protocol for alkylation of electron-rich arenes/heteroarenes with benzylic alcohols under microwave irradiation using antimony(III) chloride as catalyst has been developed. The mild reaction conditions, high yields, operational simplicity, and applicability to various substrates render the approach a useful route for the synthesis of diaryl/triarylalkane. In addition, a new route for the conversion of ortho-alkenylated phenols into functionalized O-heterocycles has been accomplished. Georg Thieme Verlag Stuttgart ? New York.
- Shukla, Prashant,Choudhary, Manoj K.,Nayak, Sandip K.
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supporting information; experimental part
p. 1585 - 1591
(2011/08/03)
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- Calcium-catalyzed hydroarylation of alkenes at room temperature
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Calcium-catalyst gaining ground: A variety of electron-poor electron-rich and trisubstituted styrene derivatives were reacted to give the desired diarylalkanes within less than an hour at room temperature in the presence of 2.5 mol % of Ca(NTf2)2/Bu4NPF6 (see scheme). Additionally the highly reactive calcium catalyst was successfully applied for the hydroarylation of dienes and even trisubstituted olefins.
- Niggemann, Meike,Bisek, Nicola
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supporting information; experimental part
p. 11246 - 11249
(2010/11/04)
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- Calcium-catalyzed friedel-crafts alkylation at room temperature
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Chemical Equatation Representation A novel calcium catalyst was found to efficiently functionalize electron-rich arenes with secondary and tertiary benzylic, propargylic, and allylic alcohols under very mild reaction conditions. The new catalyst system significantly enlarges the scope of the reaction, which was previously limited except for the few examples with secondary benzylic alcohols.
- Niggemann, Meike,Meel, Matthias J.
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supporting information; experimental part
p. 3684 - 3687
(2010/08/04)
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