NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• stereogenic trifluoromethyl centers is through enantioselective addition of enolates or their equivalents to prochiral trifluoromethyl ketones (Figure 1A). Within this area, a common catalytic approach has utilized aliphatic ketones as enolate equivalents using prolinamide, cinchona, or hybrid catalysts that

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• (NB4exp). The coupling reaction in aqueous buffer at pH 7.5 finally affords ArM 5, ArM 6 and ArM 7, respectively (Scheme 16). The obtained hybrid catalysts were tested for the RCM with substrates 21 and 64 (Table 9). Overall, ArM 6 and ArM 7 are comparable and perform best in both reactions with 35

• % conversion of substrate 21 and quantitative conversion of substrate 64. The water-soluble catalyst 9 was compared to the hybrid catalysts, displaying a higher TON in the RCM of 21 (Table 9, entry 4). Interestingly, the activity of catalyst 9 is inhibited in the presence of NB4exp (Table 9, entries 5 and 10

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• –Grubbs type hybrid catalysts active in metathesis of long-chain unsaturated esters [24]. Results and Discussion Catalyst preparation and characterization XRD patterns and texture properties (Table 1, Figure 1 A,B,C,D) of prepared MCM-22, MCM-56 and 2D-MFI zeolites proved a high quality of these supports

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

• Hynek Balcar,
• Naděžda Žilková,
• Martin Kubů,
• Michal Mazur,
• Zdeněk Bastl and
• Jiří Čejka

Beilstein J. Org. Chem. 2015, 11, 2087–2096, doi:10.3762/bjoc.11.225

• cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of

• revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6− counter anion underwent partial decomposition. Keywords: Hoveyda–Grubbs type catalyst; hybrid catalysts; lamellar zeolites; non-covalent

• −) and their immobilization on silica, and mesoporous molecular sieves MCM-41 and SBA-15 [21]. XPS analysis revealed that complexes were attached to the surface by non-covalent interactions and both cationic and anionic parts were present on the surface. The hybrid catalysts prepared were active in RCM

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• palladium/alumina (Pd/(PSi–Al2O3)) hybrid catalysts were developed. Our original Pd/(PSi–Al2O3) catalysts were used successfully in these systems and the hydrogenation of unsaturated C–C bonds and a nitro group, deprotection of a carbobenzyloxy (Cbz) group, and a dehalogenation reaction proceeded smoothly

• recovered and re-used in hydrogenation reactions in batch systems. We then developed polysilane-supported Pd/metal oxide hybrid catalysts [13] using the PI method (microencapsulation and cross-linking), which were then applied in these microreactor systems [14]. The hybrid catalysts were insoluble, did not

Hoveyda–Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

• Hynek Balcar,
• Tushar Shinde,
• Naděžda Žilková and
• Zdeněk Bastl

Beilstein J. Org. Chem. 2011, 7, 22–28, doi:10.3762/bjoc.7.4

• : alkene metathesis; catalyst immobilization; hybrid catalysts; mesoporous molecular sieves; Ru–alkylidene complexes; Introduction Ru–alkylidene complexes (Grubbs and Hoveyda–Grubbs catalysts, 1 and 2, respectively, Figure 1) belong to the most active and frequently used metathesis catalysts. These