- Synthesis of Benzofuranones via Palladium-Catalyzed Intramolecular Alkoxycarbonylation of Alkenylphenols
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Herein, a new catalytic system to synthesize benzofuranones is reported. A palladium-catalyzed intramolecular alkoxycarbonylation is employed to generate 3-substituted-benzofuran-2(3H)-ones from alkenylphenols under mild reaction conditions, linked to an ex situ formation of CO from N-formylsaccharin. The carefully chosen catalytic system enables an efficient reaction with a novel functional group tolerance, despite the high polymerization tendency of the starting material.
- Hirschbeck, Vera,Fleischer, Ivana
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- Practical, Large-Scale Preparation of Benzoxepines and Coumarins through Rhodium(III)-Catalyzed C-H Activation/Annulation Reactions
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Herein we disclose the assembly of benzoxepines and coumarins from 2-alkenylphenol precursors using [Cp*RhCl2]2 as the precatalyst and alkynes or carbon monoxide as reacting partners. The preparation of benzoxepines and coumarins can be scaled up to 33 mmol using low catalyst loadings.
- Gulías, Moisés,Marcos-Atanes, Daniel,Mascare?as, José L.,Font, Marc
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supporting information
p. 1669 - 1673
(2019/09/04)
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- Bichromatic Photosynthesis of Coumarins by UV Filter-Enabled Olefin Metathesis
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Herein, we report on a two-step bichromatic synthesis of coumarins involving UV-A and UV-C light. The first step is a UV-A-photoinduced ruthenium-catalyzed cross-metathesis (CM) reaction of 2-nitrobenzyl-protected 2-hydroxystyrenes with acrylates, using an external solution of 1-pyrenecarboxaldehyde as a UV filter. Irradiation in the absence of the filter permanently inhibits the light-activated catalyst due to photocleavage of the photolabile protecting group (PPG) and ensuing phenolate chelation to the ruthenium. The simple removal of the external filter after CM allows further photochemical reactions with UV-C light to achieve more complex architectures, such as the coumarins presented in this work. (Figure presented.).
- Eivgi, Or,Sutar, Revannath L.,Reany, Ofer,Lemcoff, N. Gabriel
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supporting information
p. 2352 - 2357
(2017/07/22)
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- Lewis Acid Catalyzed Cyclization of Propargylic Alcohols with 2-Vinylphenol
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An unprecedented Lewis acid catalyzed, protection-free, and high-efficiency synthesis of valuable 3,4-dihydro-2H-2,4-methanochromans via cycloaddition of propargylic alkynols with 2-vinylphenol is described. This cycloaddition protocol, which tolerates a
- Han, Ya-Ping,Song, Xian-Rong,Qiu, Yi-Feng,Li, Xue-Song,Zhang, Heng-Rui,Zhu, Xin-Yu,Liu, Xue-Yuan,Liang, Yong-Min
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supporting information
p. 3866 - 3869
(2016/08/16)
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- OH-directed alkynylation of 2-vinylphenols with ethynyl benziodoxolones: A fast access to terminal 1,3-enynes
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The first direct alkynylation of 2-vinylphenols was developed. The rationally optimized hypervalent iodine reagent TIPS-EBX in combination with [(CpRhCl2)2] as a C-H-activating transition metal catalyst enables the construction of a variety of highly substituted 1,3-enynes in high yields of up to 98 %. This novel C-H activation method shows excellent chemoselectivity and exclusive (Z)-stereoselectivity, and it is also remarkably mild and tolerates a variety of functional groups. Furthermore, synthetic modifications of the resulting 1,3-enynes were demonstrated. To our knowledge, this is the first example for an OH-directed C-H alkynylation with hypervalent iodine reagents.
- Finkbeiner, Peter,Kloeckner, Ulrich,Nachtsheim, Boris J.
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supporting information
p. 4949 - 4952
(2015/04/14)
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- Rhodium(III)-catalyzed dearomatizing (3 + 2) annulation of 2-alkenylphenols and alkynes
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Appropriately substituted 2-alkenylphenols undergo a mild formal [3C+2C] cycloaddition with alkynes when treated with a Rh(III) catalyst and an oxidant. The reaction, which involves the cleavage of the terminal C-H bond of the alkenyl moiety and the dearomatization of the phenol ring, provides a versatile and efficient approach to highly appealing spirocyclic skeletons and occurs with high selectivity.
- Seoane, Andrés,Casanova, Noelia,Qui?ones, Noelia,Mascare?as, José L.,Gulías, Moisés
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supporting information
p. 7607 - 7610
(2014/06/10)
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- Synthesis of spirocyclic enones by rhodium-catalyzed dearomatizing oxidative annulation of 2-alkenylphenols with alkynes and enynes
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The dearomatizing oxidative annulation of 2-alkenylphenols with alkynes and enynes proceeds with high yields and regioselectivities under RhIII catalysis. These reactions are successful using Cu(OAc)2 or air as the stoichiometric oxi
- Kujawa, Szymon,Best, Daniel,Burns, David J.,Lam, Hon Wai
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supporting information
p. 8599 - 8602
(2014/07/21)
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- Palladium(II)-catalyzed direct carboxylation of alkenyl C-H bonds with CO2
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Pd-catalyzed direct carboxylation of alkenyl C-H bonds with carbon dioxide was realized for the first time. Treatment of 2-hydroxystyrenes and a catalytic amount of Pd(OAc)2 with Cs2CO3 under atmospheric pressure of CO2 afforded corresponding coumarins in good yield. Furthermore, isolation of the key alkenylpalladium intermediate via C-H bond cleavage was achieved. The reaction was proposed to undergo reversible nucleophilic addition of the alkenylpalladium intermediate to CO2.
- Sasano, Kota,Takaya, Jun,Iwasawa, Nobuharu
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supporting information
p. 10954 - 10957
(2013/08/23)
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- Remarkable improvement achieved by imidazole derivatives in ruthenium-catalyzed hydroesterification of alkenes using formates
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Imidazole derivatives are revealed to be effective ligands in the Ru-catalyzed hydroesterification of alkenes using formates, affording one-carbonelongated esters in high yields. Further, intramolecular hydroesterification was successfully performed to give lactones for the first time. Imidazole derivatives can contribute to promote the reaction as well as to suppress the undesired decarbonylation of formate. Toxic CO gas, a directing group, and large excess alkenes are not required.
- Konishi, Hideyuki,Muto, Takashi,Manabe, Kei,Ueda, Tsuyoshi
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supporting information
p. 4722 - 4725,4
(2012/12/12)
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- Synthesis of coumarins via Pd-catalyzed oxidative cyclocarbonylation of 2-vinylphenols
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Palladium-catalyzed oxidative cyclocarbonylation of 2-vinylphenols constitutes a simple, direct method for the synthesis of coumarins. The reaction conditions, employing low pressures of CO, and air or 1,4- benzoquinone as the oxidant, are attractive in terms of environmental considerations and operational simplicity. Coumarins with a variety of functional groups were prepared in yields up to 85%.
- Ferguson, Jamie,Zeng, Fanlong,Alper, Howard
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supporting information
p. 5602 - 5605,4
(2012/12/12)
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- ortho-Effect on the acid-catalyzed hydration of 2-substituted α-methylstyrenes
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α-Methylstyrene and nine ortho-substituted analogs have been synthesized and the kinetics of their acid-catalyzed hydration in aqueous solutions of sulfuric acid at 25°C have been investigated. The kinetic acidity function HS has been constructed from the dependence of the observed rate constants kobs on the sulfuric acid concentration. The catalytic rate constants of the acid-catalyzed hydration kortho have been calculated as well. The identical shape of the kinetic acidity functions for ortho- and para-derivatives confirms what the consistent mechanism A-SE2 of the acid-catalyzed hydration has already proved for the corresponding paraderivatives. The A-SE2 mechanism involves a rate-determining proton transfer of the hydrated proton to the substrate. From the dependence of the catalytic rate constants of the ortho-derivatives on the catalytic rate constants of the para-derivatives, it is seen that the logarithm of the catalytic rate constant for hydrogen as a substituent is markedly out of the range of the other substituents and, simultaneously, that the ortho-derivatives react significantly slower than the corresponding para-derivatives. In correlation with the substitent constants σp+, a reaction constant of ρ+= -1.45 have been found. The constant is, in absolute value, considerably smaller than that for para-derivatives (ρ+ = -3.07). In parallel, the steric effects are enforced more significantly for the monoatomic substituents (slope of the Charton's constants 3.92) than for substituents including more atoms (slope of the Charton's constants 2.09). A small value of the reaction constant ρ+ has been elucidated due to the lower conjugation between the reaction centre and the benzene ring as a consequence of the geometric twist of the reaction centre out of the main aromatic plane accompanied by fading mesomeric interaction between the reaction centre and the substituents attached to the benzene ring. The isopropyl group in the carbocation is twisted less out of the aromatic plane for the monoatomic substituents and, therefore, also a small difference in the bulk of substituents has considerable steric influence on the conjugation between the carbocation and the benzene ring bearing substituents. On the contrary, the isopropyl group in the carbocations with polyatomic substituents is twisted to such a degree that changes in the bulk of substituents affect the resonant stabilization negligibly. Similar conclusions were also deduced from the correlations of the substitution constants σI and σR+.
- Prusek, Ondrej,Bures, Filip,Pytela, Oldrich
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experimental part
p. 85 - 99
(2009/06/06)
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- A mild anionic method for generating o-quinone methides: Facile preparations of ortho-functionalized phenols
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A low-temperature method for generating o-quinone methides is described which permits facile introduction of assorted R substituents onto the aryl ring system at low temperature. The method is useful for the efficient preparation of ortho-ring-alkylated phenols.
- Jones,Van De Water,Lindsey,Hoarau,Ung,Pettus
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p. 3435 - 3441
(2007/10/03)
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- Nitro substituted diphenyl ethers
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Nitro-isopropenyldiphenyl ethers are provided which can serve as a useful source of known monomer intermediates or as intermediates for the preparation of nitro-haloisopropyl substituted diphenyl ethers. The latter have been discovered to act as facile alkylating agents with phenols providing nitro-p-hydroxyphenylisopropyl substituted diphenyl ethers. When the latter compounds are reduced there are obtained the corresponding amino-p-hydroxyphenylisopropyl substituted diphenyl ethers. The polymerization of this last class of compounds with acid halides provides polyamide-esters. The polymers can be used in the manufacture of such articles as tubing, hose, bellows hose, and the like.
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