Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• Ishihara et al. using chiral copper bis(oxazoline) (S,S-11) catalysts to provide optically active mandelic acid esters 9 [75]. Among the different catalysts employed, Cu(SbF6)2 in the presence of t-butanol and (S,S)-bis oxazoline (S,S-11), afforded the desired product in 71% yield and 54

• % enantioselectivity. They employed a double asymmetric induction with (+)/(−)-menthol (12), and CuX2 bis(oxazoline) catalyst where the corresponding chiral mandelate ester 13 was obtained in 81% yield and high selectivity (90% de) (Scheme 6). The proposed mechanism of the reaction is depicted below. Hong et al

• reaction of aryl glyoxals using Cr(ClO4)3 as catalyst. Cu(II)-PhBox-catalyzed asymmetric Cannizzaro reaction. FeCl3-based chiral catalyst applied for the enantioselective intramolecular Cannizzaro reaction reported by Wu et al. Copper bis-oxazoline-catalysed intramolecular Cannizzaro reaction and proposed

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• iridium(III) photocatalyst 2-I. Subsequently, Ahneman and Doyle reported a related process for the synthesis of a variety of benzylic amines 7 by the arylation of α-amino C(sp3)‒H bonds with aryl iodides 2 involving photoredox nickel catalysis (Scheme 4) [55]. In this protocol, bis(oxazoline) (BiOx) was

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• olefins 84 as nucleophile partners and racemic secondary and tertiary α-bromo-N-protected β-lactams 83 under nickel catalysis, along with the chiral bis(oxazoline) ligand 85 and triethoxysilane (Scheme 32) [108]. Substrate structural variations on 84 had only a small impact on the reaction

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• synthesis of dendrimers and their applications as nanoreactors and catalyst carriers have been extensively studied over the last decades [94][95][96]. Fan and co-workers incorporated a bis(oxazoline)-copper(II) complex in the hydrophobic core of a polyether dendrimer [11]. The copper catalytic complex was

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• palladium by ligands which are covalently bound to the support material [12]. One example of such a catalyst was reported by our group using a bis(oxazoline) ligand bonded to 3-mercaptopropyl-functionalised silica [20]. Alternatively, the use of unsupported Pd nanoparticles or encapsulated Pd complexes are

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• (Scheme 2) [15][16][17]. A Mg-(bis)oxazoline complex serves as both a Lewis acid for the activation of α-substituted acrylates 6 towards radical addition and as a chiral template for an enantioselective hydrogen atom transfer from Bu3SnH to the α-ester radical intermediate. The authors found that the

• stoichiometric chiral Mg-(bis)oxazoline complex was required to achieve high enantioselectivity. Higher enantioselectivity was generally observed for reactions using secondary or tertiary alkyl halides. When performing radical conjugate additons to give 2-hydroxymethyl esters 7c, the authors observed a complete

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• allylated product in 93% yield and 72% ee value when cat. 2 was used (Scheme 2). Kesavan and co-workers described that the Pd/bis(oxazoline) (L1) complex can catalyze the asymmetric allylation of 3-O-Boc-oxindole, yielding the 3-allyl-3-hydroxyoxindoles in good yields (up to 93% yield) and with high

• the Cu(OTf)2 as the catalyst (10 mol %) and a fluorinated bis(oxazoline) L2 as the ligand (10 mol %), affording the products in moderate yields (up to 66% yield) and with good to excellent enantioselectivities (up to 92% ee). Interestingly, the fluorinated bis(oxazoline) L2 can be recovered and reused

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• (sp3)–H bond has gained special attention, as in the works of Muler and Boléa [9], Flynn [10], Stattery [11] and their respective co-workers. The most selective copper carbenoids are those generated from chiral bis(oxazoline) ligands in the presence of copper(I) triflate (CuOTf) (Figure 3). The rhodium

• transformation was regio and stereoselective where the main product was trans-γ-lactam (56). The chiral rhodium complexes (S)-17, (S)-18 and (S)-23 were also evaluated and yielded similar regio- and diastereoselectivity, however, with lower enantioselectivity when compared to the bis(oxazoline)/CuCl2/NaBARF

• carbene, triplet carbene and carbenoids. Classification of the carbenoid intermediates by the electronic nature of the groups attached to the divalent carbene carbon. Chiral bis(oxazoline) ligands used in enantioselective copper carbenoid insertion. Chemical structures of complexes (R)-18 and (S)-18

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• , highlighting both the accomplishments and the future work needed in this important area. Throughout the discussion below, it is clear that there are privileged ligand architectures of these copper-catalyzed alkynylations. High enantioselectivities have been achieved with pyridine bis(oxazoline) (Pybox), bis

• (oxazoline) (Box), and Quinap-type ligands (Figure 1). Review Additions to iminium ions Although this review will focus on enantioselective additions to cyclic electrophiles, it is worth noting that the first enantioselective additions of chiral copper acetylides to imines or iminium ions utilized acyclic

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• , heteroaryl, and alkyl, etc. to produce α,β-unsaturated acylimidazolidinones 215. Next, the Evan’s asymmetric DA methodology involving a [4 + 2] cycloaddition of chiral bis(oxazoline) in the presence of Cu(OTf)2 was employed to furnish the required norbornene system 216. Later, it was converted into a lactam

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• . After 3.5 h the reaction yielded 89% of the expected dimer. However, a significant change on the isomer ratio was observed. In this work, we report one example related to the direct palladation of enantiopure bis-oxazoline 7 having a chiral center at the 4-position and the substituent at the 2-position

• . Synthesis of the bis(oxazoline) coordinated complexes Synthesis of dichlorobis[(4-isopropyl-2-naphthalen-1-yl)oxazoline)]palladium(II) (9) and dichlorobis(4-isopropyl-2-(2-cyanoethyl)oxazoline)palladium(II) (12): Complexes 9 and 12 were synthesized using the same procedure. A solution of sodium

• versus temperature. Recycling experiments for Erio removal (C0 = 30 ppm, 20 mL) in the presence of catalyst 9 at pH 7 and T = 22 °C. Cyclopalladation reactions of (S)-4-isopropyl-2-(naphthalen-1-yl)oxazoline. Synthesis of cyclopalladated complex from bis-oxazoline. Synthesis of the bis(oxazoline

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• either a Sc(OTf)3–3,3′-bis(diethylaminomethyl)-1,1′-bi-2-naphthol complex (85) or Cu(OTf)2–(S,S)-2,2′-isopropylidene-bis(4-tert-butyl-2-oxazoline) complex (86) (Figure 6). The latter bis(oxazoline) and its derivatives have become common chiral ligands in Lewis acid-mediated reactions [179]. The Evans

• group has developed several methods for Diels–Alder and aldol reactions that employed chiral bis(oxazoline) copper(II) complexes [180]. Starting in 1999, Evans and co-workers published a series of papers which reported the Mukaiyama–Michael addition to various α,β-unsaturated Michael acceptors [181][182

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• reaction conditions showed that cesium fluoride proved the best base. PhI(OAc)2 was the preferred oxidant over other hypervalent iodine compounds or sources of F+ or CF3+; additionally, the presence of a bis(oxazoline) as a ligand was beneficial to the reaction, as well as that of TEMPO to prevent

Catalytic asymmetric tandem Friedel–Crafts alkylation/Michael addition reaction for the synthesis of highly functionalized chromans

• Jiahuan Peng and
• Da-Ming Du

Beilstein J. Org. Chem. 2013, 9, 1210–1216, doi:10.3762/bjoc.9.137

• diphenylamine-linked bis(oxazoline)-Zn(OTf)2 complex was investigated. This tandem reaction afforded functionalized chiral chromans in good yields with moderate to high stereoselectivities (up to 95:5 dr, up to 99% ee). Keywords: asymmetric catalysis; bis(oxazoline); chroman; Friedel–Crafts alkylation; tandem

• -linked bis(oxazoline)-Zn(II) complexes. On the other hand, indole and its derivatives are one of the most intensively investigated classical heterocycles owing to their prevalence in bioactive compounds. Indoles have been successfully utilized in asymmetric Friedel–Crafts reactions with nitroolefin and

• reaction has appeared [50]. Herein, we wish to detail our independent research on the asymmetric tandem Friedel–Crafts alkylation/Michael addition reaction of indoles with nitroolefin enoates catalyzed by bis(oxazoline)-Zn(OTf)2 complexes, resulting in functionalized chiral chromans (dihydrobenzopyrans) in

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

Bis(oxazolines) based on glycopyranosides – steric, configurational and conformational influences on stereoselectivity

• Tobias Minuth and
• Mike M. K. Boysen

Beilstein J. Org. Chem. 2010, 6, No. 23, doi:10.3762/bjoc.6.23

• excellent yields and the trans/cis ratio was in the typical range (around 70:30) obtained with bis(oxazoline) ligands [22]. However, the enantioselectivities differed dramatically for the new ligands and revealed once again the strong influence of position 3 and the pyranose conformation on the efficiency

• derivatives of gluco-configured bis(oxazoline) ligands 2 and 3 with 3-epimerisation or 3-defunctionalisation in the pyranose scaffold. Application in stereoselective cyclopropanation as a model reaction highlighted the strong impact of modifications at the pyranose position 3 on the asymmetric induction

• are currently under way. Planned modifications at pyranose position 3 of carbohydrate bis(oxazolines). Impact of structural ligand modifications on the stereoselectivity of cyclopropanations. New glucosamine-based bis(oxazoline) ligands with their pyranose conformation and application in asymmetric

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• tributyltin fluoride [112]. After protecting group manipulations and formation of the diazoester 138 with p-nitrobenzenesulfonylazide (PNBSA), the key carbene insertion was achieved using copper(I) in the presence of bis-oxazoline 139. A 9:1 ratio of 141 and 142 was obtained after direct chloranil oxidation

DBFOX- Ph/metal complexes: Evaluation as catalysts for enantioselective fluorination of 3-(2-arylacetyl)-2-thiazolidinones

• Takehisa Ishimaru,
• Norio Shibata,
• Dhande Sudhakar Reddy,
• Takao Horikawa,
• Shuichi Nakamura and
• Takeshi Toru

Beilstein J. Org. Chem. 2008, 4, No. 16, doi:10.3762/bjoc.4.16

• availability of commonly used classes of ligands for asymmetric catalysis, such as, TADDOLs [37][39][41][47], BINAPs [38][40][43][44][46][49][51][53][55][56][57] and bis(oxazoline) [33][34][36][42][45]. Of particular importance are BINAP ligands. Sodeoka et al. have used the latter ligands in asymmetric

• enantioselectivities [57]. This study is useful because, up until now, the fluorinated products obtained by Sodeoka's method have been prepared by diastereoselective methods [65][66][67]. Independently, our group has focused on the development of enantioselective fluorination and related reactions using bis(oxazoline