Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• -azabicyclo[3.1.0]hexane system 61 and the δ3-amino acid precursor 62 [50]. Epoxidations and oxaziridinations A variety of cinchona-derived phase transfer catalysts have been employed in the asymmetric epoxidation [51][52], but only one utilizes the free 6’-OH. In this report by Berkessel and co-workers

Bifunctional phase-transfer catalysis in the asymmetric synthesis of biologically active isoindolinones

• Antonia Di Mola,
• Maximilian Tiffner,
• Francesco Scorzelli,
• Laura Palombi,
• Rosanna Filosa,
• Paolo De Caprariis,
• Mario Waser and
• Antonio Massa

Beilstein J. Org. Chem. 2015, 11, 2591–2599, doi:10.3762/bjoc.11.279

• particularly promising for large scale applications. Keywords: asymmetric synthesis; Belliotti (S)-PD 172938; heterocycles; isoindolinones cascade reactions; phase transfer catalysts; Introduction Among the nitrogen heterocycles, the isoindolinone ring system is a favored scaffold, owing to the wide range of

Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

• A. John Blacker and
• Katherine E. Jolley

Beilstein J. Org. Chem. 2015, 11, 2408–2417, doi:10.3762/bjoc.11.262

• as split and recombination streams [31][32], or static mixers [32][33], can enhance mixing and mass transfer between phases. Phase-transfer catalysts (PTCs) can also be used to promote reactions across phase boundaries [31], their use would, however, incur additional financial costs for the reaction

N,N'-(Hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide): Synthesis via cyclodextrin mediated N-alkylation in aqueous solution and further Prilezhaev epoxidation

• Julian Fischer,
• Simon Millan and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2834–2840, doi:10.3762/bjoc.9.318

• adequate phase transfer catalysts and the cyclodextrin–guest complexes were characterized by 1H NMR and 2D NMR ROESY spectroscopy. Finally, the curing properties of the diepoxide with lysine-based α-amino-ε-caprolactam were analyzed by rheological measurements. Keywords: alkylation; cyclodextrins; epoxy

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

• James C. Anderson,
• Andreas S. Kalogirou,
• Michael J. Porter and
• Graham J. Tizzard

Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200

• . Enantioselective reactions have been controlled by asymmetric metal-centred Lewis acids; chiral hydrogen bond donors, in particular by the use of asymmetric thiourea organocatalysts, chiral Brønsted acids, phase-transfer catalysts and Brønsted base catalysts [3][15][25][26][27][28][29][30][31][32][33][34][35][36

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• organocatalysts. Cinchona alkaloid derivatives The first organocatalytic enantioselective desymmetrization of meso-aziridines was discovered by Hou and co-workers in 2007 [40] with various arylthiols as nucleophiles in CCl4 at 0 °C in the presence of cinchonine-derived phase-transfer catalysts (PTCs, Figure 2, OC

• enantioselectivities. In the presence of some achiral phase-transfer catalysts or phosphines such as TBAB and P(t-Bu)3, the vicinal chlorohydrins were obtained in high yields. Up to now, three classes of organocatalysts including chiral phosphoramides, chiral phosphine oxides, and chiral pyridine N-oxides were used in

One-pot tandem cyclization of enantiopure asymmetric cis-2,5-disubstituted pyrrolidines: Facile access to chiral 10-heteroazatriquinanes

• Ping-An Wang,
• Sheng-Yong Zhang and
• Henri B. Kagan

Beilstein J. Org. Chem. 2013, 9, 265–269, doi:10.3762/bjoc.9.32

• , this 10-heteroazatriquinane 7b possesses a rigid bowl-like molecular scaffold with a quaternary nitrogen site (N2) at the bottom of the cavity. Recently, Denmark and colleagues [25][26] have synthesized a series of chiral phase-transfer catalysts (chiral PTCs) based on a 2-azatriquinane skeleton

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• -catalyzed asymmetric fluorinations were discovered by others and ourselves, based on complexes of Pd(II) [46], Cu(II) [47][48][49], Ni(II) [48][50] and Ru(II) [51] as catalysts [4][51]. In parallel, organocatalytic asymmetric electrophilic fluorination of carbonyl compounds by means of phase-transfer

• catalysts [52] and small-molecule chiral amine catalysts were introduced and explored with great success [53][54][55][56]. Here we present the full range of observations on titanium-catalyzed fluorinations of β-ketoesters. The focus is on the development of the reaction and the study of factors influencing

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• and its derivatives is a synthetically useful reaction, because it allows the preparation of polycyclic structures which are relatively difficult to obtain by ground-state transformations [8]. During our attempts to develop novel ammonium-based phase-transfer catalysts [9][10][11] that are embedded

• dibenzosemibullvalene derivatives are accessable by the photoinduced di-π-methane rearrangement of appropriately substituted dibenzobarrelene substrates. With one representative example, it was demonstrated that these compounds may act as phase-transfer catalysts in alkylation reactions with comparable or even better

• performance than the commonly employed tetrabutylammonium salts. It is therefore concluded that this class of chiral compounds may be used as a promising platform for the development of versatile phase-transfer catalysts. Experimental General remarks: NMR spectra were recorded on a Bruker Avance 400 (1H NMR

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Enantioselective nucleophilic difluoromethylation of aromatic aldehydes with Me₃SiCF₂SO₂Ph and PhSO₂CF₂H reagents catalyzed by chiral quaternary ammonium salts

• Chuanfa Ni,
• Fang Wang and
• Jinbo Hu

Beilstein J. Org. Chem. 2008, 4, No. 21, doi:10.3762/bjoc.4.21

• RbOH (Table 2, entries 8 and 9). Encouraged by these results, we further examined the influence of substituents on the chiral phase transfer catalysts. As shown in Table 2, the different substituents showed some influence on the enantioselectivity. The electron-withdrawing group CF3 at C-4 position of