1444-65-1Relevant articles and documents
First example of a highly enantioselective catalytic protonation of silyl enol ethers using a novel Lewis acid-assisted Bronsted acid system
Ishihara,Nakamura,Kaneeda,Yamamoto
, p. 12854 - 12855 (1996)
-
An expedient route to heterocycles through α-arylation of ketones and arylamides by microwave induced thermal SRN1 reactions
Soria-Castro, Silvia M.,Caminos, Daniel A.,Penenory, Alicia B.
, p. 17490 - 17497 (2014)
Microwave irradiation promotes a quick aromatic nucleophilic substitution by a thermally induced electron transfer process to form new C-C bonds by the coupling of aryl radicals and enolate nucleophiles. Diverse 2-aryl-1- phenylethanones can be prepared by the direct α-arylation of acetophenone with different haloarenes. The ketone enolate anion is generated by deprotonation with tBuOK in DMSO and the reaction is carried out in a closed microwave vessel at 70-100°C for 10 min. This simple procedure also allows the synthesis of deoxybenzoin and indole heterocycle derivatives by inter- or intra-molecular ring closure reactions, with moderate to excellent substitution yields. This journal is the Partner Organisations 2014.
-
Davis et al.
, p. 124,127 (1950)
-
First Enantioselective Protonation of Prochiral Allyltrimethyltins Using Lewis Acid Assisted Chiral Br?nsted Acids
Ishihara, Kazuaki,Ishida, Yuji,Nakamura, Shingo,Yamamoto, Hisashi
, p. 758 - 760 (1997)
The LBA which is prepared from tin tetrachloride and optically active binaphthol or its monomethyl ether is a highly effective reagent for the enantioselective protonation of prochiral allyltrimethyltins. The absolute stereochemical selectivity is quite different from that in the protonation of silyl enol ethers which we reported earlier.
Synthesis of an enantiopure 2-arylcyclohexanols from prochiral enol acetates by an enantioselective protonation/diastereoselective reduction sequence
Asensio, Gregorio,Cuenca, Ana,Rodriguez, Nuria,Medio-Simon, Mercedes
, p. 3851 - 3855 (2003)
The enantioselective protonation with 2-sulfinyl alcohols of lithium enolates of 2-arylcyclohexanones with different substituents on the phenyl group takes place with excellent enantioselectivities (89-99%). Chiral 2-phenylcyclohexanone and 2-arylcyclohexanones carrying electron donor substituents on the aromatic ring are converted into the corresponding trans-2-arylcyclohexanols by diastereoselective reduction with sodium naphthalenide in the presence of acetamide. The stereochemical integrity of the tertiary stereocenter is fully preserved using this reduction procedure. Interestingly, the chiral proton source is not consumed in the synthesis.
ANOMALOUS STEREOCHEMISTRY OF GASE-PHASE ACID-INDUCED RING OPENING IN 1-PHENYLCYCLOHEXENE OXIDE
Crotti, P.,Macchia, F.,Pizzabiocca, A.,Renzi, G.,Speranza, M.
, p. 3393 - 3396 (1987)
The first experimental evidence for an entropy-driven frontside displacement in a gas-phase cationic nucleophilic substitution has been provided by the results concerning the ring opening of 1-phenylcyclohexene oxide catalized by gaseous acids.
A study of substrate specificity of toluene dioxygenase in processing aromatic compounds containing benzylic and/or remote chiral centers
Bui,Hansen,Stenstrom,Hudlicky,Ribbons
, p. 116 - 124 (2001)
A series of substituted arenes containing remote chiral centers were screened as substrates for toluene dioxygenase (TDO). The absolute stereochemistry of the new metabolites was determined by chemical and spectroscopic correlation with synthetic standards. There was no evidence for kinetic resolution; enantiomers were indiscriminately processed by the enzyme to diastereomeric pairs, which were separable upon derivatization. Some of these new metabolites are useful as synthons for morphine synthesis. Full experimental details are reported for those new compounds stable to isolation and for derivatives of those that are unstable.
Immobilization and chromatographic evaluation of novel regioselectively substituted amylose-based chiral packing materials for HPLC
Shen, Jun,Li, Pengfei,Liu, Shuangyan,Shen, Xiande,Okamoto, Yoshio
, p. 878 - 886 (2011)
The regioselectively substituted amylose derivatives bearing a 4-tert-butylbenzoate or 4-chlorobenzoate group at 2-position, and 3,5-dichlorophenylcarbamate and a small amount of 3-(triethoxysilyl) propylcarbamate groups at 3- and 6-positions were synthesized by a two-step process based on the esterification of 2-position of a glucose unit. The obtained derivatives were effectively immobilized onto macroporous silica gel by intermolecular polycondensation of triethoxysilyl groups. Their chiral recognition abilities were evaluated as chiral packing materials (CPMs) for high-performance liquid chromatography. These CPMs showed high chiral recognition as well as the conventional coated-type CPM, and can be used with the eluents-containing chloroform and tetrahydrofuran. With the extended use of these eluents, improvement of chiral recognition and reversed elution orders were realized. For some racemates, the immobilized CPM exhibited ability comparable or better to the commercial immobilized amylose- or cellulose-based columns,
Safe and Scalable Aerobic Oxidation by 2-Azaadamantan-2-ol (AZADOL)/NOx Catalysis: Large-Scale Preparation of Shi's Catalyst
Sasano, Yusuke,Sato, Hikaru,Tadokoro, Shinsuke,Kozawa, Masami,Iwabuchi, Yoshiharu
, p. 571 - 577 (2019)
A method for safe and scalable aerobic alcohol oxidation using 2-azaadamantan-2-ol (AZADOL), an azaadamantane-type hydroxylamine catalyst, with a NOx cocatalyst in a conventional batch reactor has been developed. The use of 2 mol % AZADOL and 10 mol % NaNO2 was determined to promote aerobic alcohol oxidation quantitatively within a reasonable time (8 h). Safety is ensured by controlling the reaction temperature below the flash point of the acetic acid solvent. The robustness of the developed method is demonstrated by the 500 g scale oxidation of diacetone fructose into Shi's catalyst for asymmetric epoxidation.
Enantioselective protonation/diastereoselective reduction with sodium naphthalenide-acetamide; a new synthesis of chiral trans-2-phenylcyclohexanol
Asensio, Gregorio,Cuenca,Gavina,Medio-Simon, Mercedes
, p. 3939 - 3940 (1999)
An efficient synthesis of trans-2-phenylcyclohexanol has been achieved by enantioselective protonation of the enolate of 2-phenylcyclohexanone with α-sulfinyl alcohols and subsequent reduction of the chiral ketone by sodium naphthalenide in the presence of acetamide. Interestingly, the chirality source is not consumed in the synthesis of the chiral target.
Synthesis of optically active poly(diphenylacetylene)s using polymer reactions and an evaluation of their chiral recognition abilities as chiral stationary phases for HPLC
Maeda, Katsuhiro,Maruta, Miyuki,Sakai, Yuki,Ikai, Tomoyuki,Kanoh, Shigeyoshi
, (2016)
A series of optically active poly(diphenylacetylene) derivatives bearing a chiral substituent (poly-2S) or chiral and achiral substituents (poly-(2Sx-co-31-x)) on all of their pendant phenyl rings were synthesized by the reaction of poly(bis(4-carboxyphenyl)acetylene) with (S)-1-phenylethylamine ((S)-2) or benzylamine (3) in the presence of a condensing reagent. Their chiroptical properties and chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were investigated. Poly-2S and poly-(2Sx-co-31-x) (0.06 x-co-31-x)). Furthermore, h-poly-2S and h-poly-(2S0.36-co-30.64) emitted circularly polarized luminescence with opposite signs. h-Poly-2S showed higher chiral recognition abilities toward a larger number of racemates than poly-2S without a preferred-handed helicity and the previously reported preferred-handed poly(diphenylacetylene) derivative bearing the same chiral substituent on half of its pendant phenyl rings. h-Poly-(2S0.36-co-30.64) also exhibited good chiral recognition abilities toward several racemates, though the elution order of some enantiomers was reversed compared with h-poly-2S.
Conformational control in proton sources for enantioselective protonation of samarium enolate derived from α-methoxy-substituted ketones
Mikami, Koichi,Yamaoka, Makoto,Yoshida, Akihiro,Nakamura, Yutaka,Takeuchi, Seiji,Ohgo, Yoshiaki
, p. 607 - 608 (1998)
High enantioselectivity is achieved in the asymmetric protonation of samarium enolate, regioselectively generated by SmI2-mediated reduction of 2-methoxy-substituted cydohexanones using achiral diamine- or pro-atropisomeric 2,2′-biphenol-derived chiral diols as proton sources by virtue of the conformational control.
Visible-Light Photoredox-Catalyzed Dicarbofunctionalization of Styrenes with Oxime Esters and CO2: Multicomponent Reactions toward Cyanocarboxylic Acids and γ-Keto Acids
Bai, Junxue,Li, Miao,Zhou, Cong,Sha, Yu,Cheng, Jiang,Sun, Jianwei,Sun, Song
supporting information, p. 9654 - 9658 (2021/12/14)
A photoredox-catalyzed dicarbofunctionalization of styrenes with oxime esters and CO2 has been achieved. Notably, a series of four-, five-, or six-membered cyclic ketone oximes worked well to furnish a wide range of ε-, ζ-, and η-cyanocarboxylic acids in good yields. Furthermore, a series of γ-keto acids also could be obtained by employing acyclic ketone oxime esters as the carbonyl radical precursor. It provides convergent access to diverse biologically important cyanocarboxylic and γ-keto acids.
The Silicon-Hydrogen Exchange Reaction: Catalytic Kinetic Resolution of 2-Substituted Cyclic Ketones
List, Benjamin,Zhang, Pinglu,Zhou, Hui
supporting information, p. 1953 - 1956 (2021/11/17)
We have recently reported the strong and confined, chiral acid-catalyzed asymmetric 'silicon-hydrogen exchange reaction'. One aspect of this transformation is that it enables access to enantiopure enol silanes in a tautomerizing σ-bond metathesis, via deprotosilylation of ketones with allyl silanes as the silicon source. However, until today, this reaction has not been applied to racemic, 2-substituted, cyclic ketones. We show here that these important substrates readily undergo a highly enantioselective kinetic resolution furnishing the corresponding kinetically preferred enol silanes. Mechanistic studies suggest the fascinating possibility of advancing the process to a dynamic kinetic resolution.
