- Hydrogen Bonding Networks Enable Br?nsted Acid-Catalyzed Carbonyl-Olefin Metathesis**
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Synthetic chemists have learned to mimic nature in using hydrogen bonds and other weak interactions to dictate the spatial arrangement of reaction substrates and to stabilize transition states to enable highly efficient and selective reactions. The activation of a catalyst molecule itself by hydrogen-bonding networks, in order to enhance its catalytic activity to achieve a desired reaction outcome, is less explored in organic synthesis, despite being a commonly found phenomenon in nature. Herein, we show our investigation into this underexplored area by studying the promotion of carbonyl-olefin metathesis reactions by hydrogen-bonding-assisted Br?nsted acid catalysis, using hexafluoroisopropanol (HFIP) solvent in combination with para-toluenesulfonic acid (pTSA). Our experimental and computational mechanistic studies reveal not only an interesting role of HFIP solvent in assisting pTSA Br?nsted acid catalyst, but also insightful knowledge about the current limitations of the carbonyl-olefin metathesis reaction.
- Anh To, Tuong,Pei, Chao,Koenigs, Rene M.,Vinh Nguyen, Thanh
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- AuCl3-Catalyzed Ring-Closing Carbonyl–Olefin Metathesis
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Compared with the ripeness of olefin metathesis, exploration of the construction of carbon–carbon double bonds through the catalytic carbonyl–olefin metathesis reaction remains stagnant and has received scant attention. Herein, a highly efficient AuCl3-catalyzed intramolecular ring-closing carbonyl–olefin metathesis reaction is described. This method features easily accessible starting materials, simple operation, good functional-group tolerance and short reaction times, and provides the target cyclopentenes, polycycles, benzocarbocycles, and N-heterocycle derivatives in good to excellent yields.
- Wang, Rui,Chen, Yi,Shu, Mao,Zhao, Wenwen,Tao, Maoling,Du, Chao,Fu, Xiaoya,Li, Ao,Lin, Zhihua
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supporting information
p. 1941 - 1946
(2020/02/11)
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- Regioselective Epoxidations by Cytochrome P450 3A4 Using a Theobromine Chemical Auxiliary to Predictably Produce N-Protected β- or γ-Amino Epoxides
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N-Protected β- and γ-amino epoxides are useful chiral synthons. We report here that the enzyme cytochrome P450 3A4 can catalyze the formation of such compounds in a regio- and stereoselective manner, even in the presence of multiple double bonds or aromatic substituents. To this end, the theobromine chemical auxiliary is used not only to control the selectivity of the enzyme, but also as a masked amine, and to facilitate product recovery. Theobromine predictably directed epoxidation at the double bond of the fourth carbon from the theobromine group. Unlike with most catalysts, the selectivity did not depend on electronic or steric factors but rather on the position of the olefin relative to the theobromine group. (Figure presented.).
- Polic, Vanja,Cheong, Kin Jack,Hammerer, Fabien,Auclair, Karine
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supporting information
p. 3983 - 3989
(2017/11/30)
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- Nickel-Catalyzed Stereoselective Dicarbofunctionalization of Alkynes
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A nickel-catalyzed three-component reaction involving terminal alkynes, boronic acids, and alkyl halides is presented herein. Trisubstituted alkenes can be obtained in a highly regio- and stereocontrolled manner by the simultaneous addition of both aryl and alkyl groups across the triple bond in a radical-mediated process. The reaction, devoid of air- and moisture-sensitive organometallic reagents and catalysts, is operationally simple and offers a broad scope and functional-group tolerance. Triple whammy: A nickel-catalyzed three-component reaction involving terminal alkynes, boronic acids, and alkyl halides produces trisubstituted alkenes in a highly regio- and stereocontrolled fashion. The reaction, devoid of air- and moisture-sensitive organometallic reagents and catalysts, is operationally simple and offers a broad scope and functional-group tolerance.
- Li, Zhaodong,García-Domínguez, Andrés,Nevado, Cristina
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supporting information
p. 6938 - 6941
(2016/06/13)
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- A dehydrogenative diels-alder reaction of prenyl derivatives with 2,3-dichloro-5,6-dicyanobenzoquinone
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An efficient dehydrogenative Diels-Alder (DHDA) reaction of prenyl derivatives with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) has been developed under mild conditions, leading to a series of cyclohexene derivatives with good to excellent yields and excellent diastereoselectivity.
- Feng, Hong-Xia,Wang, Yuan-Yuan,Chen, Jie,Zhou, Ling
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supporting information
p. 940 - 944
(2015/03/30)
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- Synthesis of the tricyclic core of colchicine via a dienyne tandem ring-closing metathesis reaction
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The synthesis of the tricyclic framework of colchicine has been achieved using a tandem ring-closing metathesis reaction of dienynes as the key step. In this process, both seven-membered rings B and C were formed in one step. Oxidation of tertiary allylic
- Boyer, Francois-Didier,Hanna, Issam
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p. 2293 - 2295
(2008/02/05)
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- SYNTHESIS OF THE RACEMIC AND OPTICALLY ACTIVE FORMS OF GIZZEROSINE, THE INDUCER OF GIZZARD EROSION IN CHICKS
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The racemate end both the (R)- and (S)-forms of gizzerosine were synthesised, and the (S)-isomer was identified as the toxic substance in fish meal causing severe gizzard erosion (black vomit) in chicks.
- Mori, Kenji,Sugai, Takeshi,Maeda, Yukari,Okazaki, Tomomi,Noguchi, Tadashi,Naito, Hiroshi
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p. 5307 - 5312
(2007/10/02)
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- STEREOSELEKTIVE TOTALSYNTHESE VON (+/-)-TORREYOL
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Enones of formulae Ia-d undergo cyclization to give stereoselectively the enol esters IIa-d, respectively.IIa-d are suitable synthones for some sesquiterpene syntheses.-In this paper the synthesis of torreyol (1) is described by an all step strereocontrolled reaction sequence: cyclization educt 10 (Ic) was prepared by alkylation of 8 with 5 and enol ether cleavage of 9.The reaction sequence 11a (IIc)14a 1518 (ester hydrolysis, formation of the tert. alcohol, degradation of the isopropenyl group) followed by oxidation resulted in the formation of ketone 19 whose relative configuration was determined by the 2D J-resolved 400 MHz (1)H NMR spectrum.After methylation at C-8 (2223) the tosylhydrazone 25 underwent Bamford-Stevens reaction to yield (+/-)-1.
- Franke, L.R. Rodriguez-Avial,Wolf, H.,Wray, V.
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p. 3491 - 3498
(2007/10/02)
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- Intramolecular and Intermolecular Lewis Acid Catalyzed Ene Reactions Using Ketones as Enophiles
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Alkylaluminium halide catalyzed intramolecular ene reactions of β-keto esters proceed in high yield to give cyclohexanols, via either a type I or type II process.Treatment of β-keto ester 3 with Me2AlCl gives cis-fused ene adduct 5 in 67percent yield.Simi
- Jackson, Andrew C.,Goldman, Boris E.,Snider, Barry B.
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p. 3988 - 3994
(2007/10/02)
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