Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• and practicability of this approach, a 2 mmol scale experiment of the asymmetric transfer hydrogenation of 1a was carried out (Scheme 3). Under the standard reaction conditions, 0.5 gram (98% yield) of chiral difluorinated indoline 2a was obtained with 95% ee. Based on previous studies [31], a

• chiral phosphoric acid as a Brønsted acid catalyst and Hantzsch ester as the hydrogen source, a series of 3,3-difluoro-substituted 3H-indoles underwent asymmetric transfer hydrogenation under mild reaction conditions, giving the target products with excellent yields and optical purity. Experimental

Organophosphorus chemistry: from model to application

• György Keglevich

Beilstein J. Org. Chem. 2023, 19, 89–90, doi:10.3762/bjoc.19.8

• newly prepared thiophosphorus acids were not efficient in the asymmetric transfer hydrogenation of 2-phenylquinoline. However, they may find application in other model reactions. These days, stereoselective syntheses incorporating “green" chemical considerations are of utmost importance in medicinal

Design, synthesis, and evaluation of chiral thiophosphorus acids as organocatalysts

• Karen R. Winters and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2022, 18, 1471–1478, doi:10.3762/bjoc.18.154

• asymmetric organocatalysis. In order to eliminate the need for C2-symmetry in common CPAs, various scaffolds containing C1-symmetrical thiophosphorus acids were chosen. These new compounds were synthesized and evaluated in the asymmetric transfer hydrogenation of 2-phenylquinoline. Although the efficacy of

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• ) [59]. The catenane catalyst allows for the asymmetric transfer hydrogenation of 2-substituted quinolines by Hantzsch esters in a highly stereoselective fashion [60]. It was found that the catenated catalyst gives superior stereoselectivities in comparison to the macrocyclic and the acyclic reference

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• -carbon precursor for the synthesis. The forward synthesis transformed 2-acetylfuran (20) to its corresponding alcohol 21 through an asymmetric transfer hydrogenation catalyzed by a ruthenium complex (0.5 mol %) in 98% yield with 95% ee (Scheme 2). The azeotropic mixture of HCO2H/Et3N 5:2 was employed as

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• enantioselective hydrocupration of difluorocyclopropenes in the presence of chiral diphosphine ligands using stoichiometric hydride sources that included polymethylhydrosiloxane (PMHS) and organoboranes (Scheme 35) [79]. Cossy and co-workers have achieved the catalytic asymmetric transfer hydrogenation with

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• ligands that were obtained from readily available natural (1S)-β-pinene and (1S)-α-pinene [18]. We applied these ligands for the formation of the ruthenium complexes, which were successfully used as catalysts in asymmetric transfer hydrogenation of prochiral ketones. In continuation of our studies on the

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• use of heated CSTRs would be useful to explore. The formation of both imines 20 and 21 are of interest as an asymmetric reduction would give an optically pure amine. To demonstrate this, imine 20, formed in situ, underwent asymmetric-transfer hydrogenation in both batch and flow modes, using [IrCp*Cl2

• imines reported within our study. Of these examples, the latter was further explored by immediate asymmetric-transfer hydrogenation of an in situ formed imine under continuous-flow conditions, as a potentially productive route to chiral amines. Continuous-flow process to produce and react N-chloramines

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• ]. Opatz et al. developed the enantioselective syntheses of various alkaloids using the rhodium catalyst developed by Noyori [88] for the asymmetric transfer hydrogenation of imines. Interestingly, imines are formed from unstable α-aminonitrile intermediates which spontaneously eliminate HCN [89][90][91

The enantioselective synthesis of (S)-(+)-mianserin and (S)-(+)-epinastine

• Piotr Roszkowski,
• Jan. K. Maurin and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2015, 11, 1509–1513, doi:10.3762/bjoc.11.164

• /bjoc.11.164 Abstract A simple enantioselective synthetic procedure for the preparation of mianserin and epinastine in optically pure form is described. The key step in the synthetic pathway is the asymmetric reduction of the cyclic imine using asymmetric transfer hydrogenation conditions. Keywords

• phthalimide proposed by Moffett [15] may be used for this step with comparable results. The imine 6 was then transformed to the enantiomerically enriched amine 7 with the aid of asymmetric transfer hydrogenation (ATH) process [8][10][11]. As in our synthesis of aptazepine [8], we initially used the chiral

• )-(+)-epinastine. Chirality was introduced in a key step by asymmetric transfer hydrogenation. This synthetic procedure could be used for the preparation of other compounds variously substituted at the aryl rings. The structure of mianserin 1 and epinastine 2. Catalysts used in ATH. The ORTEP diagram for X-ray

A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

• Erli Sugiono and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 2457–2462, doi:10.3762/bjoc.9.284

• dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities. Keywords: asymmetric transfer hydrogenation; binolphosphate; continuous-flow reactors; flow chemistry; microreactors; organocatalysis; photochemistry; Introduction Tetrahydroquinolines [1][2

• hand, the substrate scope of this new photocyclization–asymmetric transfer hydrogenation sequence was examined. The results are summarized in Table 2. In general, different 2-aminochalcones bearing substituted aromatic residues on both ketone and enone moieties underwent the desired photocyclization

Continuous-flow catalytic asymmetric hydrogenations: Reaction optimization using FTIR inline analysis

• Magnus Rueping,
• Teerawut Bootwicha and
• Erli Sugiono

Beilstein J. Org. Chem. 2012, 8, 300–307, doi:10.3762/bjoc.8.32

• example of a continuous-flow organocatalytic asymmetric transfer hydrogenation performed in a microreactor. In this work a ReactIR flow cell was coupled with the microreactor and applied as an inline monitoring device for optimizing the reactions. Results and Discussion The continuous-flow microreactor

• ReactIR monitoring: (a) Trend curve of product formation at different temperatures. (b) Reaction spectra showing the consumption of the substrate and the formation of product at different temperatures. (c) Three-dimensional time-resolved spectral data. Experimental setup for the asymmetric transfer

• hydrogenation. Asymmetric hydrogenation of benzoxazines. Optimization of the Brønsted acid catalyzed reduction of benzoxazines.a Scope of the Brønsted acid catalyzed reduction of benzoxazines.a Optimization of the Brønsted acid catalyzed transfer hydrogenation of quinolines.a Scope of the Brønsted acid

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• also been used as a heterogeneous support medium in continuous flow. A ruthenium catalyst complexed to a norephedrine-derived ligand 47 was immobilized onto modified (alkylsilyl-capped) silica and employed to catalyze a continuous asymmetric transfer hydrogenation [50] (Scheme 13). The use of

• of asymmetric transfer hydrogenation in flow have also been reported [51][52]. Supported catalysis has been extended to reactions involving the use of continuous flow membrane reactors [19][20][21][22]. For example, the asymmetric epoxidation of a chromene derivative 49, catalyzed by homogeneous

• ). Continuous-flow asymmetric cyclopropanation. Continuous asymmetric hydrogenation of dimethyl itaconate in scCO2. Continuous asymmetric transfer hydrogenation of acetophenone. Asymmetric epoxidation using a continuous flow membrane reactor. Enzymatic cyanohydrin formation in a microreactor. Resolution of (R/S