5340-78-3Relevant academic research and scientific papers
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.
supporting information, (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.
A 3, 3 - dimethyl butyl preparation method (by machine translation)
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Paragraph 0015-0026, (2018/01/13)
The invention discloses a 3, 3 - dimethyl butyl preparation of the preparation method, characterized in that in the ethanol, 3, 3 - dimethyl butyric acid under the acid catalysis ester, then under the action of the borohydride one pot method to obtain the final product 3, 3 - dimethyl-butanol. This invention abolishes the existing literature reports of flammable and explosive reagent (such as lithium aluminum hydride) and a solvent (such as ethyl ether) reaction conditions; in addition, the invention uses the one pot method to obtain the final product, high yield, purity is good, the price of raw materials used low, source is wide, the final product cost, applied to industrial production. (by machine translation)
Catalytic functionalization of methane and light alkanes in supercritical carbon dioxide
Fuentes, M. Angeles,Olmos, Andrea,Caballero, Ana,Perez, Pedro J.,Munoz, Bianca K.,Jacob, Kane,Etienne, Michel,Gonzalez-Nunez, M. Elena,Mello, Rossella,Asensio, Gregorio
supporting information, p. 11013 - 11018,6 (2015/01/07)
The development of catalytic methods for the effective functionalization of methane yet remains a challenge. The best system known to date is the so-called Catalytica Process based on the use of platinum catalysts to convert methane into methyl bisulfate with a TOF rate of 10-3 s. In this contribution, we report a series of silver complexes containing perfluorinated tris(indazolyl)borate ligands that catalyze the functionalization of methane into ethyl propionate upon reaction with ethyl diazoacetate (EDA) by using supercritical carbon dioxide (scCO2) as the reaction medium. The employment of this reaction medium has also allowed the functionalization of ethane, propane, butane, and isobutane.
Stereochemistry of Nucleophilic Substitution Reactions Depending upon Substituent: Evidence for Electrostatic Stabilization of Pseudoaxial Conformers of Oxocarbenium Ions by Heteroatom Substituents
Ayala, Leticia,Lucero, Claudia G.,Antoinette, Jan,Romero,Tabacco, Sarah A.,Woerpel
, p. 15521 - 15528 (2007/10/03)
Lewis acid-mediated nucleophilic substitution reactions of substituted tetrahydropyran acetates reveal that the conformational preferences of six-membered-ring cations depend significantly upon the electronic nature of the substituent. Nucleophilic substitutions of C-3 and C-4 alkyl-substituted tetrahydropyran acetates proceeded via pseudoequatorially substituted oxocarbenium ions, as would be expected by consideration of steric effects. Substitutions of C-3 and C-4 alkoxy-substituted tetrahydropyran acetates, however, proceeded via pseudoaxially oriented oxocarbenium ions. The unusual selectivities controlled by the alkoxy groups were demonstrated for a range of other heteroatom substituents, including nitrogen, fluorine, chlorine, and bromine. It is believed that the pseudoaxial conformation is preferred in the ground state of the cation because of an electrostatic attraction between the cationic carbon center of the oxocarbenium ion and the heteroatom substituent. This analysis is supported by the observation that selectivity diminishes down the halogen series, which is inconsistent with electron donation as might be expected during anchimeric assistance. The C-2 heteroatom-substituted systems gave moderately high 1,2-cis selectivity, while small alkyl substituents showed no selectivity. Only in the case of the tert-butyl group at C-2 was high 1,2-trans selectivity observed. These studies reinforce the idea that ground-state conformational effects need to be considered along with steric approach considerations.
Hydroxylation of carbanions with lithium teri-butyl peroxide acting as an oxenoid
Julia, Marc
, p. 15 - 24 (2007/10/03)
The lithium salt of terf-butyl hydroperoxide can convert alkyl, vinyl, aryl carbanions, acetylides and various enolates into the corresponding hydroxylated derivatives in good yields and under mild conditions. Eisevier.
A new chiral auxiliary for asymmetric thermal reactions: High stereocontrol in addition, allylation, and annulation reactions
Stack, Jeffrey G.,Curran, Dennis P.,Geib, Steven V.,Rebek Jr., Julius,Ballester, Pablo
, p. 7007 - 7018 (2007/10/02)
A new imide chiral auxiliary, endo-7-(2-benzoxazolyl)-1,5,7-trimethyl-3-azabicyclo[3.3.1]nonan-2-one (5), is prepared from Kemp's triacid and resolved via its menthyl carbamate. Mixed fumarate derivatives of the auxiliary show unprecedented control of regiochemistry and β-stereochemistry in representative radical addition reactions. Chiral radicals derived from 5 also show extremely high levels of stereoselectivity in representative radical allylation and cyclization reactions. Structural features of the chiral auxiliary and features of radical addition are integrated into a model for stereoselection.
Copper-catalyzed conjugate addition of organomagnesium reagents to α,β-ethylenic esters: A simple high yield procedure
Cahiez, Gerard,Alami, Mouad
, p. 7425 - 7428 (2007/10/02)
The conjugate addition of organomagnesium reagents to α, β-ethylenic esters is performed in THF, at room temperature (30 min to 1.5 h), in the presence of CuCl (3%) and Me3SiCl (1.2 eq.). Good yields of 1,4-addition products are obtained according to this very simple procedure.
Improved Synthesis of Tertiary Alkylacetic Acids and Esters
Randriamahefa, S.,Deschamps, P.,Gallo, R.,Grangette, H.
, p. 493 - 495 (2007/10/02)
Tertiary alkylacetic acids (R3CCH2COOH) are prepared by reaction of 1,1-dichloroethene with a reagent capable of forming readily a tertiary alkyl carbenium ion with sulfuric acid in the absence of boron trifluoride.With tertiary butyl reagents, the yields are good and the method is convenient at laboratory and larger scales.The yields of carboxylic acids fall sharply with increasing steric effects.The esters are obtained directly, by adding alcohols, in a one-pot synthesis; with C1-C3 alcohols the reaction is selective.
