The Palladium‐Catalyzed Aerobic Kinetic Resolution of Secondary Alcohols: Reaction Development, Scope, and Applications

Abstract

The first palladium-catalyzed enantioselective oxidation of secondary alcohols has been developed, utilizing the readily available diamine (−)-sparteine as chiral ligand and molecular oxygen as the stoichiometric oxidant. Mechanistic insights regarding the role of base and hydrogen bond donors have resulted in several improvements to the original system. Namely, addition of cesium carbonate and tert-butyl alcohol greatly enhances reaction rates, promoting rapid resolutions. The use of chloroform as solvent allows the use of ambient air as the terminal oxidant at 23 °C, resulting in enhanced catalyst selectivity. These improved reaction conditions have permitted the successful kinetic resolution of benzylic, allylic, and cyclopropyl secondary alcohols to high enantiomeric excess with good to excellent selectivity factors. This catalyst system has also been applied to the desymmetrization of meso-diols, providing high yields of enantioenriched hydroxyketones.

Evaluation of Cyclooctatetraene‐Based Aliphatic Polymers as Battery Materials: Synthesis, Electrochemical, and Thermal Characterization Supported by DFT Calculations

“…Model compounds 2-5 were synthesized from bromo-COT 6. [23] AS uzuki-Miyaurac oupling with p-tolyl boronice ster 7 [24] afforded model compound 2 in 68 %y ield (Scheme 2). For the synthesis of 3,aprocedure by Molander et al [25] was employed.…”

“…DSC measurements were performed on aD SC823 e instrument (HSS7, N 2 atmosphere, liquid N 2 cooling) by Mettler To ledo with astandard aluminum 40 mLm elting pot by Mettler To ledo. Synthesis (1E,3Z,5Z,7Z)-1-[4-(Methyl)phenyl]cycloocta-1,3,5,7-tetraene (2): Aqueous NaOH (2.5 mL, 1mm)w as added to am ixture of 2-(4methylphenyl)-4.4.5.5-tetramethyl-1.3.2-dioxaborolane [24] (7, 275 mg, 1.26 mmol) and (1Z,3Z,5Z,7Z)-1-bromocycloocta-1,3,5,7-tetraene [23] (6,3 www.chempluschem.org temperature the mixture was added to Pd(OAc) 2 (8.5 mg, 38 mmol), RuPhos (35 mg, 75 mmol), and potassium fluoride (230 mg, 3.95 mmol). (1E,3Z,5Z,7Z)-1-Bromocycloocta-1,3,5,7-tetraene (6, 320 mg, 1.75 mmol) was added, and the resulting mixture was stirred at room temperature for 24 h. The solvent was removed under reduced pressure, and Pd(OAc) 2 (5 mg, 22 mmol), RuPhos (33 mg, 71 mmol), K 2 CO 3 (725 mg, 5.2 mmol), and ad egassed mixture of toluene (10 mL) and H 2 O( 1mL) were added.…”

Short, Convergent Synthesis of Locked Retinals

“…We developed the palladium‐catalysed alkoxycarbonylation procedure based on a similar transformation of a related bromoalkene utilising only one atmosphere of CO gas,15 thus avoiding pressurised carbon monoxide 16,17. After a short optimisation, we found that the addition of tetrabutylammonium chloride resulted in quantitative conversion of bromides 5 and 6 with 6–8 mol‐% Pd(PPh 3 ) 4 as catalyst.…”

Advances in asymmetric oxidative kinetic resolution of racemic secondary alcohols catalyzed by chiral Mn(III) salen complexes

“…Recently, researchers have developed several effective non–enzymatic catalysts for the oxidative kinetic resolution (OKR) of racemic alcohols . In the last two decades, different chiral ligands with palladium, ruthenium, iridium, cobalt, iron, and manganese (Mn) metal ions have been used as catalysts for OKR of racemic secondary alcohols. In particular, chiral Mn(III) salen complexes are considered to be the most effective catalyst for the OKR of racemic secondary alcohols (Figure ) because of their facile synthesis and catalytic reaction condition with high turnover frequency.…”