16201-63-1Relevant academic research and scientific papers
(Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
supporting information, p. 1460 - 1464 (2018/04/06)
Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
Diastereoselective and enantioselective alkaline-hydrolysis of 2-aryl-1-cyclohexyl acetate: a CAL-B catalyzed deacylation/acylation tandem process
Belkacemi, Fatma Zahra,Merabet-Khelassi, Mounia,Aribi-Zouioueche, Louisa,Riant, Olivier
supporting information, p. 1644 - 1650 (2017/10/12)
Candida antarctica lipase proved to be a particularly efficient lipase for the resolution of racemic 2-arylcyclohexyl acetate in hydrolysis reaction with Na2CO3 in an organic medium. The (1R,2S)-trans-2-arylcyclohexanols 2a–2d were obtained with high ee values (up to >99%) and the selectivity reached E > 200. The influence of the enol ester and the solvent on (±)-trans-2-arylcyclohexanol in the CAL-B catalyzed acylation was also studied and compared with the deacylation. The CAL-B exhibits a better affinity for the alkaline hydrolysis reaction compared with acylation with the enol esters in the same organic solvents. The best conditions were applied to resolve a stereoisomeric mixture cis/trans-2-phenyl-1-cyclohexanol and its corresponding acetate by acylation and deacylation. The obtained results show a highly enantio- and diastereoselectivity of the CAL-B during the acylation and the deacylation in favor of the trans-(R)-enantiomer product. The resolution of a mixture of cis/trans-2-arylcyclohexanols was an easy, convenient approach to provide only one stereoisomer of a mixture of four with high enantiomeric excess.
Directed β C-H Amination of Alcohols via Radical Relay Chaperones
Wappes, Ethan A.,Nakafuku, Kohki M.,Nagib, David A.
supporting information, p. 10204 - 10207 (2017/08/10)
A radical-mediated strategy for β C-H amination of alcohols has been developed. This approach employs a radical relay chaperone, which serves as a traceless director that facilitates selective C-H functionalization via 1,5-hydrogen atom transfer (HAT) and enables net incorporation of ammonia at the β carbon of alcohols. The chaperones presented herein enable direct access to imidate radicals, allowing their first use for H atom abstraction. A streamlined protocol enables rapid conversion of alcohols to their β-amino analogs (via in situ conversion of alcohols to imidates, directed C-H amination, and hydrolysis to NH2). Mechanistic experiments indicate HAT is rate-limiting, whereas intramolecular amination is product- and stereo-determining.
Diastereoselective and Enantioselective Silylation of 2-Arylcyclohexanols
Wang, Li,Akhani, Ravish K.,Wiskur, Sheryl L.
supporting information, p. 2408 - 2411 (2015/05/27)
The silylation-based kinetic resolution of trans 2-arylcyclohexanols was accomplished by employing a triaryl silyl chloride as the derivatizing reagent with a commercially available isothiourea catalyst. The methodology is selective for the trans diastereomer over the cis, which provides an opportunity to selectively derivatize one stereoisomer out of a mixture of four. By employing this technology, a facile, convenient method to form a highly enantiomerically enriched silylated alcohol was accomplished through a one-pot reduction-silylation sequence that started with a 2-aryl-substituted ketone.
Nickel-catalyzed regiodivergent opening of epoxides with aryl halides: Co-catalysis controls regioselectivity
Zhao, Yang,Weix, Daniel J.
supporting information, p. 48 - 51 (2014/01/23)
Epoxides are versatile intermediates in organic synthesis, but have rarely been employed in cross-coupling reactions. We report that bipyridine-ligated nickel can mediate the addition of functionalized aryl halides, a vinyl halide, and a vinyl triflate to epoxides under reducing conditions. For terminal epoxides, the regioselectivity of the reaction depends upon the cocatalyst employed. Iodide cocatalysis results in opening at the less hindered position via an iodohydrin intermediate. Titanocene cocatalysis results in opening at the more hindered position, presumably via TiIII-mediated radical generation. 1,2-Disubstituted epoxides are opened under both conditions to form predominantly the trans product.
Influence of chiral thiols on the diastereoselective synthesis of γ-lactams from cyclic anhydrides
Younai, Ashkaan,Fettinger, James C.,Shaw, Jared T.
scheme or table, p. 4320 - 4327 (2012/07/28)
The synthesis of γ-lactams from both four-component and imine-anhydride reactions is reported. The synthesis of 2-phenylcyclohexanethiol is described and this compound was evaluated along with an additional seven chiral thiols. A range of selectivity and yields was observed and comparisons to established reactions are made in order to account for the observed reactivity.
Reduction of carbonyl compounds by lanthanide metal/2-propanol: In-situ generation of samarium isopropyloxide for stereoselective Meerwein-Ponndorf- Verley reduction
Fukuzawa, Shin-Ichi,Nakano, Narihito,Saitoh, Takahide
, p. 2863 - 2867 (2007/10/03)
The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The yields of alcohols were improved most effectively by the use of Sm metal, the amount of pinacol produced thus being minimized. The actual reducing agent may be samarium isopropyloxide, which mediates the Meerwein-Ponndorf-Verley-type hydride-transfer reaction, since the reaction can be carried out catalytically with respect to samarium. The stereoselectivities of the reductions of the 2- and 4-substituted cyclohexanones with Sm/iPrOH were higher than those achieved with SmI2/iPrOH or Sm/ H20. The asymmetric reduction of acetophenone could be achieved to give the 1-phenylethanol in up to 95% ee in the presence of the chiral ligand 7. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Recyclable Polyurea-Microencapsulated Pd(0) Nanoparticles: An Efficient Catalyst for Hydrogenolysis of Epoxides
Ley, Steven V.,Mitchell, Claire,Pears, David,Ramarao, Chandrashekar,Yu, Jin-Quan,Zhou, Wuzong
, p. 4665 - 4668 (2007/10/03)
(Matrix presented) Pd nanoparticles (～2 nm in size) microencapsulated in polyurea is an efficient and recyclable catalyst for reductive ring-opening hydrogenolysis of epoxides, using either HCOOH/Et3N or H2 as a hydrogen donor.
The design of novel N-4′-pyridinyl-α-methyl proline derivatives as potent catalysts for the kinetic resolution of alcohols
Priem, Ghislaine,Pelotier, Béatrice,Macdonald, Simon J. F.,Anson, Mike S.,Campbell, Ian B.
, p. 3844 - 3848 (2007/10/03)
A novel family of chiral acylation catalysts based on a N-4′-pyridinyl-α-methyl proline structure has been studied. A set of 31 compounds has been easily prepared and screened in the kinetic resolution of racemic alcohol 33 resulting in high enantioselectivities in most cases. From results obtained, H-bonding interactions between the catalyst and the substrate would appear essential to afford high enantioselectivity during the catalytic acylation. Additional solvent dependence and anhydride studies have been made to better identify the mechanism. This work has been further extended to the study of a number of structurally different alcohols. Ethanolamine derivatives in particular were found to be highly effective substrates (up to S = 18.8) in the kinetic resolution.
Diastereoselective reduction of alkenylboronic esters as a new method for controlling the stereochemistry of up to three adjacent centers in cyclic and acyclic molecules
Hupe, Eike,Marek, Ilan,Knochel, Paul
, p. 2861 - 2863 (2007/10/03)
(figure presented) cis-Boronates are readily available via a diastereoselective Pd-catalyzed reduction of tetrasubstituted alkenylboronic esters using H2. Applying the reaction conditions presented to unsaturated open-chain boronic esters allows the stereochemistry of up to three adjacent centers to be controlled.
