82520-34-1Relevant articles and documents
Enantioselective Desymmetrization of 2-Aryl-1,3-propanediols by Direct O-Alkylation with a Rationally Designed Chiral Hemiboronic Acid Catalyst That Mitigates Substrate Conformational Poisoning
Estrada, Carl D.,Ang, Hwee Ting,Vetter, Kim-Marie,Ponich, Ashley A.,Hall, Dennis G.
, (2021/04/07)
Enantioselective desymmetrization by direct monofunctionalization of prochiral diols is a powerful strategy to prepare valuable synthetic intermediates in high optical purity. Boron acids can activate diols toward nucleophilic additions; however, the design of stable chiral catalysts remains a challenge and highlights the need to identify new chemotypes for this purpose. Herein, the discovery and optimization of a bench-stable chiral 9-hydroxy-9,10-boroxarophenanthrene catalyst is described and applied in the highly enantioselective desymmetrization of 2-aryl-1,3-diols using benzylic electrophiles under operationally simple, ambient conditions. Nucleophilic activation and discrimination of the enantiotopic hydroxy groups on the diol substrate occurs via a defined chairlike six-membered anionic complex with the hemiboronic heterocycle. The optimal binaphthyl-based catalyst 1g features a large aryloxytrityl group to effectively shield one of the two prochiral hydroxy groups on the diol complex, whereas a strategically placed "methyl blocker"on the boroxarophenanthrene unit mitigates the deleterious effect of a competing conformation of the complexed diol that compromised the overall efficiency of the desymmetrization process. This methodology affords monoalkylated products in enantiomeric ratios equal or over 95:5 for a wide range of 1,3-propanediols with various 2-aryl/heteroaryl groups.
Controlling the Conformational Energy of a Phenyl Group by Tuning the Strength of a Nonclassical CH···O Hydrogen Bond: The Case of 5-Phenyl-1,3-dioxane
Bailey, William F.,Lambert, Kyle M.,Stempel, Zachary D.,Wiberg, Kenneth B.,Mercado, Brandon Q.
, p. 12116 - 12127 (2016/12/23)
Anancomeric 5-phenyl-1,3-dioxanes provide a unique opportunity to study factors that control conformation. Whereas one might expect an axial phenyl group at C(5) of 1,3-dioxane to adopt a conformation similar to that in axial phenylcyclohexane, a series of studies including X-ray crystallography, NOE measurements, and DFT calculations demonstrate that the phenyl prefers to lie over the dioxane ring in order to position an ortho-hydrogen to participate in a stabilizing, nonclassical CH···O hydrogen bond with a ring oxygen of the dioxane. Acid-catalyzed equilibration of a series of anancomeric 2-tert-butyl-5-aryl-1,3-dioxane isomers demonstrates that remote substituents on the phenyl ring affect the conformational energy of a 5-aryl-1,3-dioxane: electron-withdrawing substituents decrease the conformational energy of the aryl group, while electron-donating substituents increase the conformational energy of the group. This effect is correlated in a very linear way to Hammett substituent parameters. In short, the strength of the CH···O hydrogen bond may be tuned in a predictable way in response to the electron-withdrawing or electron-donating ability of substituents positioned remotely on the aryl ring. This effect may be profound: a 3,5-bis-CF3 phenyl group at C(5) in 1,3-dioxane displays a pronounced preference for the axial orientation. The results are relevant to broader conformational issues involving heterocyclic systems bearing aryl substituents.
Enzymatic desymmetrization of prochiral 2-substituted-1,3-diamines: Preparation of valuable nitrogenated compounds
Rios-Lombardia, Nicolas,Busto, Eduardo,Garcia-Urdiales, Eduardo,Gotor-Fernandez, Vicente,Gotor, Vicente
body text, p. 2571 - 2574 (2009/07/25)
A wide range of prochiral 1, 3-diamines were first efficiently synthesized and subsequently desymmetrized by using lipase from Pseudomonas cepacia as catalyst and diallyl carbonate as alkoxycarbonylating agent. In all cases, the amino carbamates of R-configuration were recovered. Final selective cleavage of the N-allyloxycarbonyl moiety was carried out under mild reaction conditions, which demonstrates the high versatility and potential of this chemoenzymatic route as a source of intermediates in the synthesis of related optically active nitrogenated derivatives.
Facile reduction of malonate derivatives using NaBH4/Br2: an efficient route to 1,3-diols
Tudge, Matthew,Mashima, Hiroko,Savarin, Cecile,Humphrey, Guy,Davies, Ian
, p. 1041 - 1044 (2008/09/17)
Borane-dimethoxyethane generated from sodium borohydride-bromine mixtures efficiently reduces a wide range of malonate derivatives to the corresponding 1,3-diols. This new reagent system represents a milder alternative to current methods available, providing the requisite 1,3-diols in higher yields over shorter reaction times.
First desymmetrization of 1,3-propanediamine derivatives in organic solvent. Development of a new route for the preparation of optically active amines
Bustos, Eduardo,Gotor-Fernandez, Vicente,Montejo-Bernardo, Jose,Garcia-Granda, Santiago,Gotor, Vicente
, p. 4203 - 4206 (2008/02/14)
The chemical synthesis and enzymatic desymmetrization of a panel of prochiral diamines have been successfully described for the first time using lipases in organic solvents. A family of 2-aryl-1,3-propanediamines has been obtained with high enantiopurity and good yields in the PSL-catalyzed reaction using diallyl carbonate in 1,4-dioxane.
The synthesis of phenolic propane-1, 2- and 1,3-diols as intermediates in immobilised chelatants for the borate anion
Tyman, John H. P.,Payne
, p. 691 - 695 (2007/10/03)
The isomeric 3-(hydroxyphenyl)propane-1, 2-diols have been synthesised from allylic precursors by epoxidation and cleavage. Several different methods have been examined for obtaining 1-(methoxyphenyl)propane-1, 3-diols. 2-(methoxyphenyl)propane-1, 3-diols and certain hydroxy analogues have been obtained from benzaldoximes converted by oxidation to methoxy- and benzyloxynitromethylbenzenes followed by hydroxymethylation with formaldehyde and catalytic hydrogenation.
Mesogenic, optical, and dielectric properties of 5-substituted 2-[12-(4-pentyloxyphenyl)-p-carboran-1-yl] [1,3]dioxanes
Nagamine, Takashi,Januszko, Adam,Kaszynski, Piotr,Ohta, Kiminori,Endo, Yasuyuki
, p. 3836 - 3843 (2007/10/03)
Two homologous series of carborane-containing dioxanes 1[n] and 2[n] (n = 1-10) were prepared and their mesogenic properties investigated. All compounds exhibit nematic behavior and three members of series 2[n] show an E phase. Numerical analysis of the clearing temperatures gave a limiting value T NI(∞) of 89 °C for series 2[n] and indicated conformational flexibility of the dioxane ring. Investigations of three-ring derivative 1[4] gave Δn = 0.17, S = 0.53, and Δε = +0.4 ± 0.1 at 85 °C. Extrapolation of dielectric data for dilute solutions of 1[4] in 6-CHBT gave Δε = +0.4 ± 0.25 at 24 °C. Modelling of dielectric results with the Maier-Meier equation demonstrated that conformers with a higher β angle are preferred, which is consistent with conformational selection for the most elongated conformers. The Royal Society of Chemistry 2006.
Unusual Tethering Effects in the Schmidt Reaction of Hydroxyalkyl Azides with Ketones: Cation-π and Steric Stabilization of a Pseudoaxial Phenyl Group
Katz, Christopher E.,Aube, Jeffrey
, p. 13948 - 13949 (2007/10/03)
The Lewis acid-promoted reactions of chiral 2-aryl-3-azido-1-propanols with 4-substituted cyclohexanones lead to iminium ethers and ultimately caprolactams (following a hydrolysis step). In this study, it is shown that these reactions afford variable ratios of products, depending on the electronic nature of the phenyl group. These results are interpreted in the context of a cation?π stabilizing effect in the product-determining reaction intermediate. Remarkably, the best selectivity was obtained when an azidopropanol reagent containing a quaternary center was used; a control experiment showed that the high selectivity observed in this result depended upon the free rotation of the pseudoaxial aromatic group in the intermediate that affords the major product. Copyright
Enzyme catalyzed monohydrolysis of 2-aryl-1 3-propanediol diacetates. A study of structural effects of the aryl moiety on the enantioselectivity
Guanti, Giuseppe,Narisano, Enrica,Podgorski, Tadeusz,Thea, Sergio,Williams, Andrew
, p. 7081 - 7092 (2007/10/02)
PPL catalyzed monohydrolysis of 2-aryl substituted 13-propanediol diacetates afforded the corresponding monoacetates in acceptable to fair chemical and optical yields. Electronic effects in the aromatic ring were examined. Elaboration of some 2-arylpropanediol monoacetates to optically active 2-arylpropanols and propanoic acids was performed.
