- Atroposelective Synthesis of Axially Chiral N-Arylpyrroles by Chiral-at-Rhodium Catalysis
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A transformation of fluxional into configurationally stable axially chiral N-arylpyrroles was achieved with a highly atroposelective electrophilic aromatic substitution catalyzed by a chiral-at-metal rhodium Lewis acid. Specifically, N-arylpyrroles were alkylated with N-acryloyl-1H-pyrazole electrophiles in up to 93 percent yield and with up to >99.5 percent ee, and follow-up conversions reveal the synthetic utility of this new method. DFT calculations elucidate the origins of the observed excellent atroposelectivity.
- Chen, Shuming,Han, Feng,Houk, K. N.,Ivlev, Sergei,Meggers, Eric,Xie, Xiulan,Ye, Chen-Xi
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supporting information
p. 13552 - 13556
(2020/06/05)
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- Enantioselective Palladium-Catalyzed Decarboxylative Allylation of β-Keto Esters Assisted by a Thiourea
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Enantioselective intramolecular decarboxylative allylation of β-keto esters catalyzed by a palladium bis(phosphine)-thiourea complex is reported. This procedure is not only effective for β-keto esters, but also effective for β-keto amides. An intermolecular variant of the asymmetric decarboxylative allylation is also established. DFT calculations indicate that an outer-sphere mechanism is viable for the decarboxylative allylation of β-keto esters.
- Qian, Hua,Gu, Guoxian,Zhou, Qinghai,Lu, Jiaxiang,Chung, Lung Wa,Zhang, Xumu
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- Ring expansion of cyclic β-amino alcohols induced by diethylaminosulfur trifluoride: Synthesis of cyclic amines with a tertiary fluorine at C3
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As the replacement of a hydrogen atom by a fluorine atom in a compound can have an important impact on its biological properties, the development of methods allowing the introduction of a fluorine atom is of great importance. The scope and limitations of
- Anxionnat, Bruno,Robert, Benoit,George, Pascal,Ricci, Gino,Perrin, Marc-Antoine,Gomez Pardo, Domingo,Cossy, Janine
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experimental part
p. 6087 - 6099
(2012/09/11)
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- Solvent-controlled highly selective bis-and monoallylation of active methylene compounds by allyl acetate with palladium(0) nanoparticle
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(Chemical Equation Presented) Palladium(0) nanoparticle has been used as an efficient catalyst for the allylation of active methylene compounds. Very efficient bisallylation is achieved for a variety of active methylene compounds by allyl acetate and its derivatives in one stroke in THF solvent. The reaction in water provides monoallylated product selectively by allyl acetate only. The recovered Pd(0) nanoparticle is recycled. A probable mechanism is suggested.
- Ranu, Brindaban C.,Chattopadhyay, Kalicharan,Adak, Laksmikanta
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p. 4595 - 4598
(2008/03/12)
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- Studies on diastereoselective reduction of cyclic β-ketoesters with boron hydrides. Part 4: The reductive profile of functionalized cyclohexanone derivatives
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Reduction of 2-allyl-2-carboalkoxycyclohexanones (3d-f), 2-propyl-2-carboethoxycyclohexanone (3g) and 2-benzyl-2- carboethoxycyclohexanone (3h) with boron hydrides in the presence and absence of several chelating agents were studied. Molecular modeling studies using semiempirical PM3 method were performed in order to find a suitable explanation of the diastereoselection of ketone carbonyl faces during the reductive process, which yielded trans-2-allyl-2-carboethoxycyclohexanol (6e) and cis-2-allyl-2-carboethoxycyclohexanol (7e) in good diastereomeric excess by using inexpensive sodium and tetrabutylammonium borohydrides.
- Fraga, Carlos A.M.,Teixeira, Lis Helena P.,Menezes, Carla Maria De S.,Sant'Anna, Carlos Mauricio R.,Ramos, Maria Da Concei??o K.V.,De Aquino Neto, Francisco R.,Barreiro, Eliezer J.
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p. 2745 - 2755
(2007/10/03)
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- Ring-closing metathesis/fragmentation route to geometrically defined medium-ring cycloalkenes: Total synthesis of (±)-periplanone C
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The combination of alkene metathesis and β-fragmentation offers an efficient entry into (Z)-configured medium-ring cycloalkenes. The versatility of this method is demonstrated by the total synthesis of Periplanone C, a semiochemical of Periplaneta america
- Ivkovic, Aleksandar,Matovic, Radomir,Saicic, Radomir N.
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p. 1221 - 1224
(2007/10/03)
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- A new tetratertiary phosphine ligand and its use in Pd-catalyzed allylic substitution
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A new tetraphosphine, the cis-cis-cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane (Tedicyp) 1 has been synthesized, characterized, and used in Pd-catalyzed allylic substitutions. The Tedicyp was easily prepared in seven steps from the commercially available himic anhydride. The structure of the complex Tedicyp-borane was determined by X-ray analysis. The tetraphosphine in combination with [Pd(η3-C3H5)Cl]2 affords a very efficient catalyst for allylic substitution of several allylic acetates. Under mild conditions, very high turnover numbers and turnover frequencies have been obtained.
- Laurenti,Feuerstein,Pepe,Doucet,Santelli
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p. 1633 - 1637
(2007/10/03)
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- PREPARATION OF OPTICALLY ACTIVE TRICYCLIC 1,4-DIOXEPIN-5-ONE DERIVATIVES AND ITS APPLICATION TO ASYMMETRIC ALKYLATION
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Chiral bicyclic α,β-unsaturated lactones (6a,b and 8a,b) were easily synthesized from chiral cyclic diols (2-4) and cyclic β-keto esters (1a,b).Alkylation of 8b proceeded in a highly diastereoselective manner to afford a quaternary carbon.
- Kato, Keisuke,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 413 - 424
(2007/10/02)
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- Asymmetric Alkylation Using Chiral Cyclic Diols to Prepare a Quaternary Carbon
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Asymmetric alkylation of cyclic and acyclic β-keto ester acetals (4, 5, 13, 14, and 18) with C2-symmetric cycloalkane-1,2-dioxy moiety proceeded in a highly diastereoselective manner to afford enol ethers (9-12, 15-17, 19a-c) with a chiral quat
- Kato, Keisuke,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 3315 - 3326
(2007/10/02)
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- Stereoselective reactions. XXI. Asymmetric alkylation of α-alkyl β-keto esters to α,α-dialkyl β-keto esters having either (R)- Or (S)-chiral quaternary center depending on the solvent system
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Asymmetric alkylation reaction of chiral enamines prepared from α-alkyl β-keto esters and (S)-valine tert-butyl ester leading to either enantiomer is described. Lithiated chiral enamines can be alkylated with alkyl halides in a toluene solvent in the presence of HMPA to give, after hydrolysis, α,α-dialkyl β-keto esters in 70-99%ee. The reactions in the presence of THF, dioxolane, or trimethylamine, instead of HMPA, afford the corresponding antipodes with enantiomeric purities of 44-92%ee. The present method provides a procedure for the synthesis of both enantiomers of α,α-dialkyl β-keto esters in high enantiomeric purities starting from the same chiral enamines.
- Ando, Kaori,Takemasa, Yataka,Tomioka, Kiyoshi,Koga, Kenji
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p. 1579 - 1588
(2007/10/02)
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- Enzyme-mediated enantioface-differentiating hydrolysis of α-substituted cycloalkanone enol esters
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A new type of enzymatic hydrolysis, enantioface-differentiating hydrolysis of enol esters, is disclosed. As a result of screening, Pichia miso IAM 4682, a type of yeast, was selected as the best strain to perform the enantioselective hydrolysis of enol esters to give α-chiral ketones. For example, incubation of 1-acetoxy-2-methylcyclohexene (4a) with P. miso afforded (S)-2-methylcyclohexanone (5) in high optical yield. This enzymatic hydrolysis is applicable to various α-substituted cycloalkanone enol esters, and thereby chiral six-, eight-, ten-, and twelve-membered-ring ketones of 70-96% enantiomeric excess (ee) are easily prepared.
- Matsumoto, Kazutsugu,Tsutsumi, Seiji,Ihori, Tamiko,Ohta, Hiromichi
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p. 9614 - 9619
(2007/10/02)
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- Alkylation of Active Methylene compounds by Allylic Alcohols using Tetrakis(triphenylphosphine)palladium(0) Catalysts
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We have found that active methylene compounds can be alkylated by allylic alcohols using (PPh3)4Pd as a catalyst at 100 deg C without prior activation of the allylic hydroxy group.
- Bergbreiter, David E.,Weatherford, David A.
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p. 883 - 884
(2007/10/02)
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- PREPARATION OF THERMODINAMICALLY STABLE ENOL SILYL ETHERS OF γ,δ-UNSATURATED KETONES BY PALLADIUM-CATALYZED DECARBOXYLATION-ALLYLATION OF ALLYL 2,3-DISUBSTITUTED 3-TRIMETHYLSILOXYACRYLATES
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Allyl 2,3-disubstituted 3-trimethylsiloxyacrylates underwent palladium-catalyzed intramolecular decarboxylation-allylation to afford enol silyl ethers of γ,δ-unsaturated ketones.
- Tsuji, Jiro,Ohashi, Yukihiro,Minami, Ichiro
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p. 2397 - 2398
(2007/10/02)
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- FACTORS CONTROLLING THE DIASTEREOFACE SELECTIVITY IN THE COMPLEMENTARY ASYMMETRIC ALKYLATION OF α-ALKYL β-KETO ESTERS
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Complementary asymmetric alkylation reaction of the lithioenamine derived from 2-methoxycarbonylcyclohexanone and (S)-valine tert-butyl ester was examined by employing the various electron pair donating additives in a toluene solvent, in order to clarify
- Tomioka, Kiyoshi,Ando, Kaori,Takemasa, Yutaka,Koga, Kenji
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p. 5677 - 5680
(2007/10/02)
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